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Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2018	Feb. 19, 2019	Jun. 29, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Trading Symbol	EXR
Entity Registrant Name	Extra Space Storage Inc.
Entity Central Index Key	0001289490
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Smaller Reporting Company	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		127,298,501
Entity Public Float			$ 12,155,910,603

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Assets:
Real estate assets, net	$ 7,491,831	$ 7,132,431
Investments in unconsolidated real estate ventures	125,326	75,907
Cash and cash equivalents	57,496	55,683
Restricted cash	15,194	30,361
Other assets, net	158,131	166,571
Total assets	7,847,978	7,460,953
Liabilities, Noncontrolling Interests and Equity:
Notes payable, net	4,137,213	3,738,497
Exchangeable senior notes, net	562,374	604,276
Notes payable to trusts, net	30,928	117,444
Revolving lines of credit	81,000	94,000
Cash distributions in unconsolidated real estate ventures	45,197	5,816
Accounts payable and accrued expenses	101,461	96,087
Other liabilities	104,383	81,026
Total liabilities	5,062,556	4,737,146
Commitments and contingencies
Extra Space Storage Inc. stockholders' equity:
Preferred stock, $0.01 par value, 50,000,000 shares authorized, no shares issued or outstanding	0	0
Common stock, $0.01 par value, 500,000,000 shares authorized, 127,103,750 and 126,007,091 shares issued and outstanding at December 31, 2018 and December 31, 2017, respectively	1,271	1,260
Additional paid-in capital	2,640,705	2,569,485
Accumulated other comprehensive income	34,650	33,290
Accumulated deficit	(262,902)	(253,284)
Total Extra Space Storage Inc. stockholders' equity	2,413,724	2,350,751
Noncontrolling interest represented by Preferred Operating Partnership units, net	153,096	159,636
Noncontrolling interests in Operating Partnership, net and other noncontrolling interests	218,602	213,420
Total noncontrolling interests and equity	2,785,422	2,723,807
Total liabilities, noncontrolling interests and equity	$ 7,847,978	$ 7,460,953

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	50,000,000	50,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares issued (in shares)	127,103,750	126,007,091
Common stock, shares outstanding (in shares)	127,103,750	126,007,091

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues:
Property rental	$ 1,039,340	$ 967,229	$ 864,742
Tenant reinsurance	115,507	98,401	87,291
Management fees and other income	41,757	39,379	39,842
Total revenues	1,196,604	1,105,009	991,875
Expenses:
Property operations	291,695	271,974	250,005
Tenant reinsurance	25,707	19,173	15,555
Acquisition related costs and other	0	0	12,111
General and administrative	81,256	78,961	81,806
Depreciation and amortization	209,050	193,296	182,560
Total expenses	607,708	563,404	542,037
Gain on real estate transactions, earnout on prior acquisitions and impairment of real estate	30,807	112,789	8,465
Income from operations	619,703	654,394	458,303
Interest expense	(178,436)	(153,511)	(133,479)
Non-cash interest expense related to amortization of discount on equity component of exchangeable senior notes	(4,687)	(5,103)	(4,980)
Interest income	5,292	6,736	10,998
Income before equity in earnings of unconsolidated real estate ventures and income tax expense	441,872	502,516	330,842
Equity in earnings of unconsolidated real estate ventures	14,452	15,331	12,895
Equity in earnings of unconsolidated real estate ventures - gain on sale of real estate assets and purchase of joint venture partners' interests	0	0	69,199
Income tax expense	(9,244)	(3,625)	(15,847)
Net income	447,080	514,222	397,089
Net income allocated to Preferred Operating Partnership noncontrolling interests	(13,995)	(14,989)	(14,700)
Net income allocated to Operating Partnership and other noncontrolling interests	(17,796)	(20,220)	(16,262)
Net income attributable to common stockholders	$ 415,289	$ 479,013	$ 366,127
Earnings per common share
Basic (in dollars per share)	$ 3.29	$ 3.79	$ 2.92
Diluted (in dollars per share)	$ 3.27	$ 3.76	$ 2.91
Weighted average number of shares
Basic (in shares)	126,087,487	125,967,831	125,087,554
Diluted (in shares)	133,159,033	134,155,771	125,948,076

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 447,080	$ 514,222	$ 397,089
Other comprehensive income:
Change in fair value of interest rate swaps	1,430	17,308	24,598
Total comprehensive income	448,510	531,530	421,687
Less: comprehensive income attributable to noncontrolling interests	31,861	35,997	32,438
Comprehensive income attributable to common stockholders	$ 416,649	$ 495,533	$ 389,249

- Definition

The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

+ References

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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Redemption of Operating Partnership units for sale of property	Redemption of Operating Partnership units for common stock and cash	Redemption of Operating Partnership units for cash	Preferred Operating Partnership, Series A	Preferred Operating Partnership, Series B	Preferred Operating Partnership, Series C	Preferred Operating Partnership, Series D	Operating Partnership	Operating Partnership Redemption of Operating Partnership units for sale of property	Operating Partnership Redemption of Operating Partnership units for common stock and cash	Operating Partnership Redemption of Operating Partnership units for cash	Operating Partnership Redemption of Operating Partnership units for stock	Other	Common Stock	Common Stock Redemption of Operating Partnership units for common stock and cash	Common Stock Redemption of Operating Partnership units for stock	Additional Paid-in Capital	Additional Paid-in Capital Redemption of Operating Partnership units for common stock and cash	Additional Paid-in Capital Redemption of Operating Partnership units for cash	Accumulated Other Comprehensive Income	Accumulated Deficit
Beginning balance at Dec. 31, 2015	$ 2,372,604				$ 14,189	$ 41,902	$ 10,730	$ 13,710	$ 202,834					$ 162	$ 1,241			$ 2,431,754			$ (6,352)	$ (337,566)
Beginning balance (in shares) at Dec. 31, 2015															124,119,531
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon the exercise of options (in shares)	97,855														97,855
Issuance of common stock upon the exercise of options	$ 1,444														$ 0			1,444
Restricted stock grants issued (in shares)															119,931
Restricted stock grants issued	2														$ 2
Restricted stock grants cancelled (in shares)															(9,947)
Issuance of common stock, net of offering costs (in shares)															1,381,300
Issuance of common stock, net of offering costs	123,422														$ 14			123,408
Compensation expense related to stock-based awards	8,045																	8,045
Issuance of Operating Partnership units in conjunction with acquisitions	7,247								7,247
Redemption or purchase of noncontrolling interests		$ (7,689)	$ (506)						800	$ (7,689)	$ (1,083)			(162)				(638)	$ 577
Redemption of Operating Partnership units (in shares)																23,850
Issuance of Preferred D Units in the Operating Partnership in conjunction with acquisitions	67,193							67,193										0
Repurchase of equity portion of 2013 exchangeable senior notes (in shares)															148,940
Repurchase of equity portion of 2013 exchangeable senior notes	(872)														$ 2			(874)
Net income (loss)	397,089				7,645	2,514	2,570	1,971	16,262													366,127
Other comprehensive income	24,598				201				1,275												23,122
Tax effect from vesting of restricted stock grants and stock option exercises	2,404																	2,404
Distributions to Operating Partnership units held by noncontrolling interests	(30,997)				(7,650)	(2,514)	(2,570)	(1,971)	(16,292)
Dividends paid on common stock	(367,818)																					(367,818)
Ending balance at Dec. 31, 2016	$ 2,596,166				14,385	41,902	10,730	80,903	203,354					0	$ 1,259			2,566,120			16,770	(339,257)
Ending balance (in shares) at Dec. 31, 2016															125,881,460
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon the exercise of options (in shares)	38,418														38,418
Issuance of common stock upon the exercise of options	$ 1,266																	1,266
Restricted stock grants issued (in shares)															95,392
Restricted stock grants issued															$ 1			(1)
Restricted stock grants cancelled (in shares)															(8,179)
Compensation expense related to stock-based awards	9,561																	9,561
Issuance of Operating Partnership units in conjunction with acquisitions	7,618								7,618
Redemption or purchase of noncontrolling interests				$ (2,510)								$ (1,238)								$ (1,272)
Issuance of Preferred D Units in the Operating Partnership in conjunction with acquisitions	11,161							11,161
Noncontrolling interest in consolidated joint venture	216													216
Repurchase of equity portion of 2013 exchangeable senior notes	(6,189)																	(6,189)
Net income (loss)	514,222				6,300	2,514	2,703	3,472	20,317					(97)								479,013
Other comprehensive income	17,308				106				682												16,520
Tax effect from vesting of restricted stock grants and stock option exercises	0
Distributions to Operating Partnership units held by noncontrolling interests	(31,972)				(5,851)	(2,514)	(2,703)	(3,472)	(17,432)
Dividends paid on common stock	(393,040)																					(393,040)
Ending balance at Dec. 31, 2017	$ 2,723,807				14,940	41,902	10,730	92,064	213,301					119	$ 1,260			2,569,485			33,290	(253,284)
Ending balance (in shares) at Dec. 31, 2017	126,007,091														126,007,091
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon the exercise of options (in shares)	54,575														54,575
Issuance of common stock upon the exercise of options	$ 1,169																	1,169
Restricted stock grants issued (in shares)															85,066
Restricted stock grants issued	1														$ 1			0
Restricted stock grants cancelled (in shares)															(11,771)
Issuance of common stock, net of offering costs (in shares)															933,789
Issuance of common stock, net of offering costs	90,231														$ 10			90,221
Compensation expense related to stock-based awards	11,176																	11,176
Repayment of receivable for preferred operating units pledged as collateral on loan	495						495
Issuance of Operating Partnership units in conjunction with acquisitions	1,877								1,877
Redemption or purchase of noncontrolling interests				$ (2,558)								$ (1,126)	$ (1,337)							$ (1,432)
Redemption of Operating Partnership units (in shares)																	35,000
Conversion of Preferred C Units in the Operating Partnership for Common Operating Partnership Units							(6,851)		6,851
Noncontrolling interest in consolidated joint venture	122													122
Repurchase of equity portion of 2013 exchangeable senior notes	(31,251)																	(31,251)
Net income (loss)	447,080				5,035	2,514	2,731	3,715	17,797					(1)								415,289
Other comprehensive income	1,430				12				58												1,360
Tax effect from vesting of restricted stock grants and stock option exercises	0
Distributions to Operating Partnership units held by noncontrolling interests	(33,250)				(5,231)	(2,514)	(2,731)	(3,715)	(19,059)
Dividends paid on common stock	(424,907)																					(424,907)
Ending balance at Dec. 31, 2018	$ 2,785,422				$ 14,756	$ 41,902	$ 4,374	$ 92,064	$ 218,362					$ 240	$ 1,271			$ 2,640,705			$ 34,650	$ (262,902)
Ending balance (in shares) at Dec. 31, 2018	127,103,750														127,103,750

Consolidated Statements of Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Stockholders' Equity [Abstract]
Dividends paid on common stock (in dollars per share)	$ 3.36	$ 3.12	$ 2.93

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income	$ 447,080	$ 514,222	$ 397,089
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	209,050	193,296	182,560
Amortization of deferred financing costs	14,286	12,289	12,922
Non-cash interest expense related to amortization of discount on equity component of exchangeable senior notes	4,687	5,103	4,980
Non-cash interest expense related to amortization of premium on notes payable	0	0	(872)
Compensation expense related to stock-based awards	11,176	9,561	8,045
Gain on sale of real estate assets and purchase of joint venture partners' interests	0	0	(69,199)
Gain on real estate transactions, earnout on prior acquisitions and impairment of real estate	(30,807)	(112,789)	(8,465)
Distributions from unconsolidated real estate ventures in excess of earnings	6,867	4,567	3,534
Changes in operating assets and liabilities:
Other assets	(1,664)	(12,728)	(1,614)
Accounts payable and accrued expenses	2,736	(10,515)	10,075
Other liabilities	14,384	(5,631)	208
Net cash provided by operating activities	677,795	597,375	539,263
Cash flows from investing activities:
Acquisition of real estate assets	(426,388)	(653,185)	(1,086,523)
Development and redevelopment of real estate assets	(60,677)	(31,746)	(23,279)
Proceeds from sale of real estate assets, investments in real estate ventures and other assets	52,458	312,165	60,813
Investment in unconsolidated real estate ventures	(65,500)	(17,944)	(28,241)
Return of investment in unconsolidated real estate ventures	49,130	581	16,953
Issuance of notes receivable	(13,850)	0	(26,429)
Principal payments received from notes receivable	25,226	44,869	42,785
Purchase of equipment and fixtures	(4,297)	(7,819)	(4,968)
Net cash used in investing activities	(443,898)	(353,079)	(1,048,889)
Cash flows from financing activities:
Proceeds from the sale of common stock, net of offering costs	90,231	0	123,424
Proceeds from notes payable and revolving lines of credit	1,413,030	1,325,623	1,900,357
Principal payments on notes payable and revolving lines of credit	(1,109,854)	(1,088,679)	(1,122,442)
Principal payments on notes payable to trusts	(88,662)	0	0
Deferred financing costs	(12,302)	(6,967)	(17,486)
Repurchase of exchangeable senior notes	(80,270)	(19,916)	(22,195)
Net proceeds from exercise of stock options	1,169	1,266	1,444
Proceeds from termination of interest rate cap	0	0	1,650
Payment of earnout from prior acquisition	0	0	(4,600)
Redemption of Operating Partnership units held by noncontrolling interests	(2,558)	(2,510)	(506)
Contributions from noncontrolling interests	122	201	0
Dividends paid on common stock	(424,907)	(393,040)	(367,818)
Distributions to noncontrolling interests	(33,250)	(31,972)	(30,997)
Net cash (used in) provided by financing activities	(247,251)	(215,994)	460,831
Net increase (decrease) in cash, cash equivalents, and restricted cash	(13,354)	28,302	(48,795)
Cash, cash equivalents, and restricted cash, beginning of the period	86,044	57,742	106,537
Cash, cash equivalents, and restricted cash end of the period	72,690	86,044	57,742
Supplemental schedule of cash flow information
Interest paid	159,474	136,202	122,265
Income taxes paid	730	5,648	14,864
Redemption of Operating Partnership units held by noncontrolling interests for common stock
Common stock and paid-in capital	1,337	0	577
Tax effect from vesting of restricted stock grants and option exercises
Other assets	0	0	2,404
Additional paid-in capital	0	0	(2,404)
Acquisitions of real estate assets
Real estate assets	457,617	627,462
Notes payable assumed	(87,500)	(24,055)
Investment in unconsolidated real estate ventures			0
Accrued construction costs and capital expenditures
Acquisition of real estate assets	778	3,509	8,497
Development and redevelopment of real estate assets	554	1,703	125
Accounts payable and accrued expenses	(1,332)	(5,212)	(8,622)
Distribution of real estate from investments in unconsolidated real estate ventures
Real estate assets, net	0	0	25,055
Investments in unconsolidated real estate ventures	0	0	(25,055)
Disposition of real estate assets
Real estate assets, net	0	0	(7,869)
Issuance of Preferred OP Units for additional investment in unconsolidated real estate venture
Preferred OP Units issued	0	(4,351)	0
Investment in unconsolidated real estate ventures	0	4,351	0
Acquisitions of real estate assets
Acquisitions of real estate assets
Real estate assets	88,842	51,455	84,163
Value of Operating Partnership units issued	(1,877)	(14,428)	(74,440)
Notes payable assumed	(87,500)	(24,055)	(9,723)
Investment in unconsolidated real estate ventures	535	(12,957)
Other noncontrolling interests	0	(15)	0
Operating Partnership units redeemed
Redemption of Operating Partnership units held by noncontrolling interests for common stock
Noncontrolling interests in Operating Partnership	(1,337)	0	(577)
Disposition of real estate assets
Operating Partnership units redeemed	0	0	7,869
Acquisition of noncontrolling interests
Acquisition of noncontrolling interests
Operating Partnership units issued	0	0	(800)
Other noncontrolling interests	0	0	162
Additional paid-in capital	$ 0	$ 0	$ 638

Description of Business	12 Months Ended
Description of Business	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
DESCRIPTION OF BUSINESS	DESCRIPTION OF BUSINESS Extra Space Storage Inc. (the “Company”) is a fully integrated, self-administered and self-managed real estate investment trust (“REIT”), formed as a Maryland corporation on April 30, 2004, to own, operate, manage, acquire, develop and redevelop professionally managed self-storage properties located throughout the United States. The Company was formed to continue the business of Extra Space Storage LLC and its subsidiaries, which had engaged in the self-storage business since 1977. The Company’s interest in its stores is held through its operating partnership, Extra Space Storage LP (the “Operating Partnership”), which was formed on May 5, 2004. The Company’s primary assets are general partner and limited partner interests in the Operating Partnership. This structure is commonly referred to as an umbrella partnership REIT, or UPREIT. The Company invests in stores by acquiring wholly-owned stores or by acquiring an equity interest in real estate entities. At December 31, 2018, the Company had direct and indirect equity interests in 1,111 storage facilities. In addition, the Company managed 536 stores for third parties bringing the total number of stores which it owns and/or manages to 1,647. These stores are located in 39 states, Washington, D.C. and Puerto Rico. The Company also offers tenant reinsurance at its owned and managed stores that insures the value of goods in the storage units.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Basis of Presentation

The consolidated financial statements are presented on the accrual basis of accounting in accordance with U.S. generally accepted accounting principles (“GAAP”) and include the accounts of the Company and its wholly- or majority-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.

Certain amounts previously reported in the consolidated financial statements have been reclassified in the accompanying consolidated financial statements to conform to the current period’s presentation, primarily to change the presentation of Gain on real estate transactions, earnout from prior acquisitions, and impairment of real estate on the consolidated statement of operations. The Company has included Gain on real estate transactions, earnout from prior acquisitions, and impairment of real estate as a component of Income from operations to present gain and losses on sales of properties in accordance with ASC 360-10-45-5. The change was made for the prior periods as the Securities and Exchange Commission has eliminated Rule 3-15(a) of Regulation S-X as part of Release No. 33-10532; 34-83875; IC-33203, which had required REITs to present gain and losses on sale of properties outside of continuing operations in the statement of operations.

Immaterial Correction to Consolidated Balance Sheets

In connection with the preparation of the financial statements for the quarter ended March 31, 2018, the Company determined that the negative balances in the "Investments in unconsolidated real estate ventures" line should be presented separately as liabilities. As a result, $5,816 should have been reported as "Cash distributions in unconsolidated real estate ventures" as of December 31, 2017. The Company concluded that the amount was not material to the consolidated balance sheet as of December 31, 2017 but has elected to present these amounts as liabilities in the accompanying financial statements for consistent presentation. The classification error had no effect on the previously reported consolidated statements of operations, comprehensive income, stockholders' equity or cash flows for the year ended December 31, 2017.

Variable Interest Entities

The Company accounts for arrangements that are not controlled through voting or similar rights as variable interest entities (“VIEs”). An enterprise is required to consolidate a VIE if it is the primary beneficiary of the VIE. A VIE is created when (i) the equity investment at risk is not sufficient to permit the entity to finance its activities without additional subordinated financial support from other parties, or (ii) the entity’s equity holders as a group either: (a) lack the power, through voting or similar rights, to direct the activities of the entity that most significantly impact the entity’s economic performance, (b) are not obligated to absorb expected losses of the entity if they occur, or (c) do not have the right to receive expected residual returns of the entity if they occur. If an entity is deemed to be a VIE, the enterprise that is deemed to have a variable interest, or combination of variable interests, that provides the enterprise with a controlling financial interest in the VIE, is considered the primary beneficiary and must consolidate the VIE.

The Company has concluded that under certain circumstances when the Company enters into arrangements for the formation of joint ventures, a VIE may be created under condition (i), (ii) (b) or (c) of the previous paragraph. For each VIE created, the Company has performed a qualitative analysis, including considering which party, if any, has the power to direct the activities most significant to the economic performance of each VIE and whether that party has the obligation to absorb losses of the VIE or the right to receive benefits from the VIE that could be significant to the VIE. If the Company is determined to be the primary beneficiary of the VIE, the assets, liabilities and operations of the VIE are consolidated with the Company’s financial statements. Additionally, the Operating Partnership has notes payable to one trust that is a VIE under condition (ii)(a) above. Since the Operating Partnership is not the primary beneficiary of the trust, this VIE is not consolidated.

The Company’s investments in real estate joint ventures, where the Company has significant influence, but not control, and joint ventures which are VIEs in which the Company is not the primary beneficiary, are recorded under the equity method of accounting on the accompanying consolidated financial statements.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Fair Value Disclosures

Derivative financial instruments

Currently, the Company uses interest rate swaps to manage its interest rate risk. The valuation of these instruments is determined using widely accepted valuation techniques including discounted cash flow analysis on the expected cash flows of each derivative. This analysis reflects the contractual terms of the derivatives, including the period to maturity, and uses observable market-based inputs, including interest rate curves. The fair values of interest rate swaps are determined using the market standard methodology of netting the discounted future fixed cash payments and the discounted expected variable cash receipts. The variable cash receipts are based on an expectation of future interest rates (forward curves) derived from observable market interest rate forward curves.

The Company incorporates credit valuation adjustments to appropriately reflect both its own nonperformance risk and the respective counterparty’s nonperformance risk in the fair value measurements. In adjusting the fair value of its derivative contracts for the effect of nonperformance risk, the Company has considered the impact of netting and any applicable credit enhancements, such as collateral postings, thresholds, mutual puts, and guarantees. In conjunction with the Financial Accounting Standard Board’s fair value measurement guidance, the Company made an accounting policy election to measure the credit risk of its derivative financial instruments that are subject to master netting agreements on a net basis by counterparty portfolio.

Although the Company has determined that the majority of the inputs used to value its derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with its derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default by itself and its counterparties. However, as of December 31, 2018, the Company has assessed the significance of the impact of the credit valuation adjustments on the overall valuation of its derivative positions and has determined that the credit valuation adjustments are not significant to the overall valuation of its derivatives. As a result, the Company has determined that its derivative valuations in their entirety are classified in Level 2 of the fair value hierarchy.

The table below presents the Company’s assets and liabilities measured at fair value on a recurring basis as of December 31, 2018, aggregated by the level in the fair value hierarchy within which those measurements fall.



				Fair Value Measurements at Reporting Date Using
Description	December 31, 2018			Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)			Significant Unobservable Inputs (Level 3)
Other assets - Cash Flow Hedge Swap Agreements	$	42,324		$	—	$	42,324		$	—
Other liabilities - Cash Flow Hedge Swap Agreements	$	(2,131	)	$	—	$	(2,131	)	$	—

There were no transfers of assets and liabilities between Level 1 and Level 2 during the year ended December 31, 2018. The Company did not have any significant assets or liabilities that are re-measured on a recurring basis using significant unobservable inputs as of December 31, 2018 or 2017.

Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis

Long-lived assets held for use are evaluated for impairment when events or circumstances indicate there may be impairment. The Company reviews each store at least annually to determine if any such events or circumstances have occurred or exist. The Company focuses on stores where occupancy and/or rental income have decreased by a significant amount. For these stores, the Company determines whether the decrease is temporary or permanent, and whether the store will likely recover the lost occupancy and/or revenue in the short term. In addition, the Company reviews stores in the lease-up stage and compares actual operating results to original projections.

When the Company determines that an event that may indicate impairment has occurred, the Company compares the carrying value of the related long-lived assets to the undiscounted future net operating cash flows attributable to the assets. An impairment loss is recorded if the net carrying value of the assets exceeds the undiscounted future net operating cash flows attributable to the assets. The impairment loss recognized equals the excess of net carrying value over the related fair value of the assets.

When real estate assets are identified by management as held for sale, the Company discontinues depreciating the assets and estimates the fair value of the assets, net of selling costs. The Company compares the carrying value of the related long-lived assets to the undiscounted future net operating cash flows attributable to the assets (categorized within Level 3 of the fair value hierarchy). If the estimated fair value, net of selling costs, of the assets that have been identified as held for sale is less than the net carrying value of the assets, the Company would recognize a loss on the assets held for sale. The operations of assets held for sale or sold during the period are presented as part of normal operations for all periods presented.

The Company assesses annually whether there are any indicators that the value of the Company’s investments in unconsolidated real estate ventures may be impaired and when events or circumstances indicate that there may be impairment. An investment is impaired if management’s estimate of the fair value of the investment is less than its carrying value. To the extent impairment has occurred, and is considered to be other than temporary, the loss is measured as the excess of the carrying amount of the investment over the fair value of the investment.

As of December 31, 2018 and 2017, the Company did not have any assets or liabilities measured at fair value on a nonrecurring basis.

Fair Value of Financial Instruments

The carrying values of cash and cash equivalents, restricted cash, receivables, other financial instruments included in other assets, accounts payable and accrued expenses, variable-rate notes payable, revolving lines of credit and other liabilities reflected in the consolidated balance sheets at December 31, 2018 and 2017, approximate fair value.

The fair values of the Company’s notes receivable from Preferred Operating Partnership unit holders and other fixed rate notes receivable were based on the discounted estimated future cash flow of the notes (categorized within Level 3 of the fair value hierarchy); the discount rate used approximated the current market rate for loans with similar maturities and credit quality. The fair values of the Company’s fixed rate notes payable and notes payable to trusts were estimated using the discounted estimated future cash payments to be made on such debt (categorized within Level 3 of the fair value hierarchy); the discount rates used approximated current market rates for loans, or groups of loans, with similar maturities and credit quality. The fair value of the Company’s exchangeable senior notes was estimated using an average market price for similar securities obtained from a third party.

The fair values of the Company’s fixed-rate assets and liabilities were as follows for the periods indicated:



	December 31, 2018				December 31, 2017
	Fair Value		Carrying Value		Fair Value		Carrying Value
Notes receivable from Preferred and Common Operating Partnership unit holders	$	115,467	$	119,735	$	113,683	$	120,230
Fixed rate notes receivable	$	—	$	—	$	20,942	$	20,608
Fixed rate notes payable and notes payable to trusts	$	2,985,731	$	3,022,414	$	2,774,242	$	2,815,085
Exchangeable senior notes	$	620,149	$	575,000	$	719,056	$	624,259

Real Estate Assets

Real estate assets are stated at cost, less accumulated depreciation. Direct and allowable internal costs associated with the development, construction, renovation, and improvement of real estate assets are capitalized. Interest, property taxes, and other costs associated with development incurred during the construction period are capitalized. The construction period begins when expenditures for the real estate assets have been made and activities that are necessary to prepare the asset for its intended use are in progress. The construction period ends when the asset is substantially complete and ready for its intended use.

Expenditures for maintenance and repairs are charged to expense as incurred. Major replacements and betterments that improve or extend the life of the asset are capitalized and depreciated over their estimated useful lives. Depreciation is computed using the straight-line method over the estimated useful lives of the buildings and improvements, which are generally between five and 39 years.

Stores purchased at the time of certificate of occupancy issuance and stores purchased subsequent to the Company's adoption of ASU 2017-01 on January 1, 2017 are considered asset acquisitions. As such, the purchase price is allocated to the real estate assets acquired based on their relative fair values, which are estimated using significant unobservable inputs. The value of the tangible assets, consisting of land and buildings, is determined as if vacant. Intangible assets, which represent the value of existing tenant relationships, are recorded at their relative fair values based on the avoided cost to replace the current leases. The Company measures the value of tenant relationships based on the rent lost due to the amount of time required to replace existing customers, which is based on the Company’s historical experience with turnover in its stores. Any debt assumed as part of the acquisition is recorded at fair value based on current interest rates compared to contractual rates. Acquisition-related transactions costs are capitalized as part of the purchase price.

Intangible lease rights represent: (1) purchase price amounts allocated to leases on three stores that cannot be classified as ground or building leases; these rights are amortized to expense over the life of the leases and (2) intangibles related to ground leases on eight stores where the leases were assumed by the Company at rates that were lower than the current market rates for similar leases. The values associated with these assumed leases were recorded as intangibles, which will be amortized over the lease terms.

Real Estate Sales

In general, sales of real estate and related profits/losses are recognized when all consideration has changed hands and risks and rewards of ownership have been transferred. Certain types of continuing involvement preclude sale treatment and related profit recognition; other forms of continuing involvement allow for sale recognition but require deferral of profit recognition.

Investments in Unconsolidated Real Estate Ventures

The Company’s investments in real estate joint ventures, where the Company has significant influence, but not control and joint ventures which are VIEs in which the Company is not the primary beneficiary, are recorded under the equity method of accounting in the accompanying consolidated financial statements.

Under the equity method, the Company’s investment in real estate ventures is stated at cost and adjusted for the Company’s share of net earnings or losses and reduced by distributions. Equity in earnings of real estate ventures is generally recognized based on the Company’s ownership interest in the earnings of each of the unconsolidated real estate ventures. For the purposes of presentation in the statement of cash flows, the Company follows the “look through” approach for classification of distributions from joint ventures. Under this approach, distributions are reported under operating cash flow unless the facts and circumstances of a specific distribution clearly indicate that it is a return of capital (e.g., a liquidating dividend or distribution of the proceeds from the joint venture’s sale of assets), in which case it is reported as an investing activity.

Cash and Cash Equivalents

The Company’s cash is deposited with financial institutions located throughout the United States and at times may exceed federally insured limits. The Company considers all highly liquid debt instruments with a maturity date of three months or less to be cash equivalents.

Restricted Cash

Restricted cash is comprised of letters of credit and escrowed funds deposited with financial institutions located throughout the United States relating to earnest money deposits on potential acquisitions, real estate taxes, insurance and capital expenditures.

Other Assets

Other assets consist of equipment and fixtures, rents receivable from our tenants, investments in trusts, notes and other receivables, other intangible assets, deferred tax assets, prepaid expenses and the fair value of interest rate swaps. Depreciation of equipment and fixtures is computed on a straight-line basis over three to five years.

Derivative Instruments and Hedging Activities

The Company records all derivatives on the balance sheet at fair value. The accounting for changes in the fair value of derivatives depends on the intended use of the derivative, whether the Company has elected to designate a derivative in a hedging relationship and apply hedge accounting and whether the hedging relationship has satisfied the criteria necessary to apply hedge accounting. Derivatives designated and qualifying as a hedge of the exposure to changes in the fair value of an asset, liability or firm commitment attributable to a particular risk, such as interest rate risk, are considered fair value hedges. Derivatives designated and qualifying as a hedge of the exposure to variability in expected future cash flows, or other types of forecasted transactions, are considered cash flow hedges. Hedge accounting generally provides for the matching of the timing of gain or loss recognition on the hedging instrument with the recognition of the changes in the fair value of the hedged asset or liability that are attributable to the hedged risk in a fair value hedge or the earnings effect of the hedged forecasted transactions in a cash flow hedge. The Company may enter into derivative contracts that are intended to economically hedge certain of its risk, even though hedge accounting does not apply or the Company elects not to apply hedge accounting. The Company made an accounting policy election to measure the credit risk of its derivative financial instruments that are subject to master netting agreements on a net basis by counterparty portfolio.

Risk Management and Use of Financial Instruments

In the normal course of its ongoing business operations, the Company encounters economic risk. There are three main components of economic risk: interest rate risk, credit risk and market risk. The Company is subject to interest rate risk on its interest-bearing liabilities. Credit risk is the risk of inability or unwillingness of tenants to make contractually required payments. Market risk is the risk of declines in the value of stores due to changes in rental rates, interest rates or other market factors affecting the value of stores held by the Company. The Company has entered into interest rate swap agreements to manage a portion of its interest rate risk.

Exchange of Common Operating Partnership Units

Redemption of common Operating Partnership units for shares of common stock, when redeemed under the original provisions of the Operating Partnership agreement, are accounted for by reclassifying the underlying net book value of the units from noncontrolling interest to the Company’s equity.

Revenue and Expense Recognition

Rental revenues are recognized as earned based upon amounts that are currently due from tenants. Leases are generally on month-to-month terms. Prepaid rents are recognized on a straight-line basis over the term of the leases. Promotional discounts are recognized as a reduction to rental income over the promotional period. Late charges, administrative fees and merchandise sales are recognized as income when earned. Equity in earnings of unconsolidated real estate entities is recognized based on the Company's ownership interest in the earnings of each of the unconsolidated real estate entities. Interest income is recognized as earned.

The Company's management fees are earned subject to the terms of the related management services agreements ("MSAs"). These MSAs provide that the Company will perform management services, which include leasing and operating the property and providing accounting, marketing, banking, maintenance and other services. These services are provided in exchange for monthly management fees, which are based on a percentage of revenues collected from stores owned by third parties and unconsolidated joint ventures. MSAs generally have original terms from three to five years, after which management services are provided on a month-to-month basis unless terminated. Management fees are due on the last day of each calendar month that management services are provided.

The Company accounts for the management services provided to a customer as a single performance obligation which are rendered over time each month. The total amount of consideration from the contract is variable as it is based on monthly revenues, which are influenced by multiple factors, some of which are outside the Company's control. Therefore, the Company recognizes the revenue at the end of each month once the uncertainty is resolved. Due to the standardized terms of the MSAs, the Company accounts for all MSAs in a similar, consistent manner. Therefore, no disaggregated information relating to MSAs is presented.

Property expenses, including utilities, property taxes, repairs and maintenance and other costs to manage the facilities are recognized as incurred. The Company accrues for property tax expense based upon invoice amounts and estimates. If these estimates are incorrect, the timing of expense recognition could be affected.

Tenant reinsurance premiums are recognized as revenue over the period of insurance coverage. The Company records an unpaid claims liability at the end of each period based on existing unpaid claims and historical claims payment history. The unpaid claims liability represents an estimate of the ultimate cost to settle all unpaid claims as of each period end, including both reported but unpaid claims and claims that may have been incurred but have not been reported. The Company uses a third party claims administrator to adjust all tenant reinsurance claims received. The administrator evaluates each claim to determine the ultimate claim loss and includes an estimate for claims that may have been incurred but not reported. Annually, a third party actuary evaluates the adequacy of the unpaid claims liability. Prior year claim reserves are adjusted as experience develops or new information becomes known. The impact of such adjustments is included in the current period operations. The unpaid claims liability is not discounted to its present value. Each tenant chooses the amount of insurance coverage they want through the tenant reinsurance program. Tenants can purchase policies in amounts of 2,000 dollars to 10,000 dollars of insurance coverage in exchange for a monthly fee. As of December 31, 2018, the average insurance coverage for tenants was approximately 2,900 dollars. The Company’s exposure per claim is limited by the maximum amount of coverage chosen by each tenant. The Company purchases reinsurance for losses exceeding a set amount for any one event. The Company does not currently have any amounts recoverable under the reinsurance arrangements.

For the years ended December 31, 2018, 2017 and 2016, the number of claims made were 7,870, 5,671 and 4,055, respectively. The following table presents information on the portion of the Company’s unpaid claims liability, which is included in other liabilities on the Company's consolidated balance sheets, that relates to tenant insurance for the periods indicated:



	For the Year Ended December 31,
Tenant Reinsurance Claims:	2018			2017			2016
Unpaid claims liability at beginning of year	$	5,167		$	3,896		$	3,908
Claims and claim adjustment expense for claims incurred in the current year	15,800			11,700			7,250
Claims and claim adjustment expense (benefit) for claims incurred in the prior years	107			(203		)	87
Payments for current year claims	(11,010		)	(8,895		)	(5,423		)
Payments for prior year claims	(2,738		)	(1,331		)	(1,926		)
Unpaid claims liability at the end of the year	$	7,326		$	5,167		$	3,896

Advertising Costs

The Company incurs advertising costs primarily attributable to digital and other advertising. These costs are expensed as incurred. The Company recognized $16,153, $14,410 and $12,867 in advertising expense for the years ended December 31, 2018, 2017 and 2016, respectively, which are included in property operating expenses on the Company’s consolidated statements of operations.

Income Taxes

The Company has elected to be treated as a REIT under Sections 856 through 860 of the Internal Revenue Code of 1986, as amended (the "Internal Revenue Code"). In order to maintain its qualification as a REIT, among other things, the Company is required to distribute at least 90% of its REIT taxable income to its stockholders and meet certain tests regarding the nature of its income and assets. As a REIT, the Company is not subject to federal income tax with respect to that portion of its income which meets certain criteria and is distributed annually to stockholders. The Company plans to continue to operate so that it meets the requirements for taxation as a REIT. Many of these requirements, however, are highly technical and complex. For any taxable year that the Company fails to qualify as a REIT and for which applicable statutory relief provisions did not apply, we would be taxed at the regular corporate rates on all of our taxable income for at least that year and the ensuing four years. The Company is subject to certain state and local taxes. Provision for such taxes has been included in income tax expense on the Company’s consolidated statements of operations. For the year ended December 31, 2018, 0% (unaudited) of all distributions to stockholders qualified as a return of capital.

The Company has elected to treat its corporate subsidiary, Extra Space Management, Inc. (“ESMI”), as a taxable REIT subsidiary (“TRS”). In general, the Company’s TRS may perform additional services for tenants and may engage in any real estate or non-real estate related business. A TRS is subject to federal corporate income tax. ESM Reinsurance Limited, a wholly-owned subsidiary of ESMI, generates income from insurance premiums that are subject to federal corporate income tax and state insurance premiums tax.

Deferred tax assets and liabilities are determined based on differences between financial reporting and tax bases of assets and liabilities. At December 31, 2018 and 2017, there were no material unrecognized tax benefits. Interest and penalties relating to uncertain tax positions will be recognized in income tax expense when incurred. As of December 31, 2018 and 2017, the Company had no interest or penalties related to uncertain tax provisions.

Stock-Based Compensation

The measurement and recognition of compensation expense for all share-based payment awards to employees and directors are based on estimated fair values. Awards granted are valued at fair value and any compensation expense is recognized over the service periods of each award.

Earnings Per Common Share

Basic earnings per common share is computed using the two-class method by dividing net income attributable to common stockholders by the weighted average number of common shares outstanding during the period. All outstanding unvested restricted stock awards contain rights to non-forfeitable dividends and participate in undistributed earnings with common stockholders; accordingly, they are considered participating securities that are included in the two-class method. Diluted earnings per common share measures the performance of the Company over the reporting period while giving effect to all potential common shares that were dilutive and outstanding during the period. The denominator includes the weighted average number of basic shares and the number of additional common shares that would have been outstanding if the potential common shares that were dilutive had been issued, and is calculated using either the two-class, treasury stock or as if-converted method, whichever is most dilutive. Potential common shares are securities (such as options, convertible debt, Series A Participating Redeemable Preferred Units (“Series A Units”), Series B Redeemable Preferred Units (“Series B Units”), Series C Convertible Redeemable Preferred Units (“Series C Units”), Series D Redeemable Preferred Units (“Series D Units” and together with the Series A Units, Series B Units and Series C Units, the “Preferred OP Units") and common Operating Partnership units (“OP Units”)) that do not have a current right to participate in earnings of the Company but could do so in the future by virtue of their option, redemption or conversion right.

In computing the dilutive effect of convertible securities, net income is adjusted to add back any changes in earnings in the period associated with the convertible security. The numerator also is adjusted for the effects of any other non-discretionary changes in income or loss that would result from the assumed conversion of those potential common shares. In computing diluted earnings per common share, only potential common shares that are dilutive (those that reduce earnings per common share) are included. For the years ended December 31, 2018, 2017 and 2016, options to purchase approximately 36,075, 45,286, and 88,552 shares of common stock, respectively, were excluded from the computation of earnings per share as their effect would have been anti-dilutive.

For the purposes of computing the diluted impact of the potential exchange of the Preferred OP Units for common shares upon redemption, where the Company has the option to redeem in cash or shares and where the Company has stated the intent and ability to settle the redemption in shares, The Company divided the total value of the Preferred OP Units by the average share price of $90.30 for the year ended December 31, 2018.

The following table presents the number of weighted OP Units and Preferred OP Units, and the potential common shares, that were excluded from the computation of earnings per share as their effect would have been anti-dilutive:



	For the Year Ended December 31,
	2018	2017	2016
	Equivalent Shares (if converted)	Equivalent Shares (if converted)	Equivalent Shares (if converted)
Common OP Units	—	—	5,564,631
Series A Units (Variable Only)	—	—	875,480
Series B Units	464,033	533,174	499,966
Series C Units	312,075	377,135	353,646
Series D Units	1,019,524	—	552,796
	1,795,632	910,309	7,846,519

The Operating Partnership had $575,000 of its 3.125% Exchangeable Senior Notes due 2035 (the “2015 Notes”) issued and outstanding as of December 31, 2018. The 2015 Notes could potentially have a dilutive impact on the Company’s earnings per share calculations. The 2015 Notes are exchangeable by holders into shares of the Company’s common stock under certain circumstances per the terms of the indenture governing the 2015 Notes. The exchange price of the 2015 Notes was $92.80 per share as of December 31, 2018, and could change over time as described in the indenture. The Company has irrevocably agreed to pay only cash for the accreted principal amount of the 2015 Notes relative to its exchange obligations, but retained the right to satisfy the exchange obligation in excess of the accreted principal amount in cash and/or common stock.

Though the Company has retained that right, Accounting Standards Codification (“ASC”) 260, “Earnings per Share,” requires an assumption that shares would be used to pay the exchange obligation in excess of the accreted principal amount, and requires that those shares be included in the Company’s calculation of weighted average common shares outstanding for the diluted earnings per share computation. As of December 31, 2018, the Company had repaid the principal and accrued interest of its Exchangeable Senior Notes due 2033 (the “2013 Notes”), and therefore, no shares underlying the 2013 Notes were included in the dilution calculation for 2018. For the years ended December 31, 2017 and 2016, 344,430 shares and 309,730 shares, respectively, related to the 2013 Notes were included in the computation for diluted earnings per share. For the years ended December 31, 2018, 2017 and 2016, no shares related to the 2015 Notes were included in the computation for diluted earnings per share as the exchange price exceeded the per share price of the Company’s common stock during this period.

For the purposes of computing the diluted impact on earnings per share of the potential exchange of Series A Units for common shares upon redemption, where the Company has the option to redeem in cash or shares and where the Company has stated the positive intent and ability to settle at least $101,700 of the instrument in cash (or net settle a portion of the Series A Units against the related outstanding note receivable), only the amount of the instrument in excess of $101,700 is considered in the calculation of shares contingently issuable for the purposes of computing diluted earnings per share as allowed by ASC 260-10-45-46.

The computation of earnings per share is as follows for the periods presented:



	For the Year Ended December 31,
	2018			2017			2016
Net income attributable to common stockholders	$	415,289		$	479,013		$	366,127
Earnings and dividends allocated to participating securities	(723		)	(975		)	(792		)
Earnings for basic computations	414,566			478,038			365,335
Earnings and dividends allocated to participating securities	723			—			792
Income allocated to noncontrolling interest - Preferred Operating Partnership Units and Operating Partnership Units	22,831			30,088			—
Fixed component of income allocated to noncontrolling interest - Preferred Operating Partnership (Series A Units)	(2,288		)	(3,119		)	—
Net income for diluted computations	$	435,832		$	505,007		$	366,127

Weighted average common shares outstanding:
Average number of common shares outstanding - basic	126,087,487			125,967,831			125,087,554
OP Units	5,675,547			5,590,831			—
Series A Units	875,480			875,480			—
Series D Units	—			1,081,561			—
Unvested restricted stock awards included for treasury stock method	244,215			—			299,585
Shares related to exchangeable senior notes and dilutive stock options	276,304			640,068			560,937
Average number of common shares outstanding - diluted	133,159,033			134,155,771			125,948,076
Earnings per common share
Basic	$	3.29		$	3.79		$	2.92
Diluted	$	3.27		$	3.76		$	2.91

Recently Issued Accounting Standards

In May 2014, the Financial Accounting Standards Board ("FASB") issued ASU 2014-9, “Revenue from Contracts with Customers,” ("Topic 606") which amends the guidance for revenue recognition to replace numerous, industry-specific requirements and converges areas under this topic with those of the International Financial Reporting Standards. Topic 606 outlines a five-step process for customer contract revenue recognition that focuses on transfer of control, as opposed to transfer of risk and rewards. The amendment also requires enhanced disclosures regarding the nature, amount, timing and uncertainty of revenues and cash flows from contracts with customers. Topic 606 became effective for annual and interim periods beginning after December 15, 2017. The Company determined that its property rental revenue and tenant reinsurance revenue are not subject to the guidance in Topic 606, as they qualify as lease contract and insurance contracts, which are excluded from its scope. The Company's management fee revenue is included in the scope of Topic 606, and revenue recognized under the standard does not differ materially from revenue recognized under previous guidance. The Company adopted the standard using the modified retrospective transition method as of January 1, 2018. The Company's adoption of Topic 606 did not result in a cumulative catch-up adjustment or any significant changes to financial statement line items.

In February 2016, the FASB issued ASU 2016-02, "Leases (Topic 842)," which modifies the accounting for leases, intending to increase transparency and comparability of organizations by requiring balance sheet presentation of leased assets and increased financial statement disclosure of leasing arrangements. ASU 2016-02 will require entities to recognize a liability for their lease obligations and a corresponding asset representing the right to use the underlying asset over the lease term. Lease obligations are to be measured at the present value and accounted for using the effective interest method. The accounting for the leased asset will differ slightly depending on whether the agreement is deemed to be a financing or operating lease. For finance leases, the leased asset is depreciated on a straight-line basis and recorded separately from the interest expense in the statements of operations, resulting in higher expense in the earlier part of the lease term. For operating leases, the depreciation and interest expense components are combined, recognized evenly over the term of the lease, and presented as a reduction to operating income. ASU 2016-02 requires that assets and liabilities be presented or disclosed separately, and requires additional disclosure of certain qualitative and quantitative information related to these lease agreements. ASU 2016-02 is effective for annual periods beginning after December 15, 2018. The Company plans to adopt the standard using the modified retrospective approach as of January 1, 2019. The Company expects to elect the package of practical expedients upon adoption, which allows for the application of the standard solely to the transition period in 2019 but does not require application to prior fiscal comparative periods presented. The Company estimates that the cumulative catch-up adjustment recorded upon adoption will not have a significant impact on retained earnings. The primary impact is expected to be related to the Company's 23 operating ground leases and two corporate facility leases under which it serves as lessee. The Company estimates the lease assets and lease liabilities to be between $90,000 and $110,000 related to its operating leases upon the adoption of Topic 842.

In October 2016, the FASB issued ASU 2016-18, "Statement of Cash Flows (Topic 230): Restricted Cash," which requires that a statement of cash flows explains the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Therefore, amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. This guidance is effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. The Company adopted this guidance as of January 1, 2018, and now presents restricted cash along with cash and cash equivalents in its consolidated statements of cash flows. Prior periods have been reclassified to conform to the current year's presentation.

In January 2017, the FASB issued ASU 2017-01, "Business Combinations (Topic 805) - Clarifying the Definition of a Business," which provides guidance on whether transactions should be accounted for as acquisitions or disposals of assets or businesses. Specifically, when substantially all of the fair value of the gross assets acquired (or disposed of) is concentrated in a single identifiable asset or a group of similar identifiable assets, the set is not a business. Additionally, ASU 2017-01 also provides other guidance providing a more robust framework to use in determining whether a set of assets and activities is a business. This guidance is effective for annual periods beginning after December 15, 2017. Early application of ASU 2017-01 is permitted for transactions for which the acquisition or disposition date occurs before the issuance date or effective date of the amendments, only when the transaction has not been reported in financial statements that have been issued. The Company adopted the guidance in ASU 2017-01 prospectively to new acquisitions beginning on January 1, 2017. The adoption of this guidance resulted in a decrease in acquisition related costs, as the Company's acquisition of operating stores are considered asset acquisitions rather than business combinations under ASU 2017-01, and such costs are capitalized under the new guidance.

In August 2017, the FASB issued ASU 2017-12, "Derivatives and Hedging (Topic 815): Targeted Improvements for Accounting for Hedging Activities," which amends and simplifies existing guidance for the financial reporting of hedging relationships to allow companies to better portray the economic effects of risk management activities in their financial statements. ASU 2017-12 is effective for annual periods beginning after December 15, 2018, with early adoption permitted. The Company adopted this standard on January 1, 2018. The adoption of this standard did not have a material impact on the Company's financial statements.

In August 2018, the FASB issued ASU 2018-15, "Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40): Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That is a Service Contract." ASU 2018-15 amends the accounting for implementation costs incurred in a hosting arrangement that is a service contract, and aligns them with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. ASU 2018-15 also requires that entities amortize the capitalized implementation costs over the term of the hosting arrangement. ASU 2018-15 is effective for annual periods beginning after December 15, 2020, with early adoption permitted, including early adoption in any interim period. The Company adopted this guidance on a prospective basis as of October 1, 2018. The adoption of this standard did not have a material impact on the Company's financial statements.

Real Estate Assets

12 Months Ended

Dec. 31, 2018

Real Estate [Abstract]

Real Estate Assets

REAL ESTATE ASSETS

The components of real estate assets are summarized as follows:



	December 31, 2018			December 31, 2017
Land - operating	$	1,825,133		$	1,731,915
Land - development	7,359			13,246
Buildings, improvements and other intangibles	6,743,355			6,286,762
Intangible assets - tenant relationships	119,557			114,375
Intangible lease rights	12,443			12,443
	8,707,847			8,158,741
Less: accumulated depreciation and amortization	(1,262,438		)	(1,060,060		)
Net operating real estate assets	7,445,409			7,098,681
Real estate under development/redevelopment	46,422			33,750
Net real estate assets	$	7,491,831		$	7,132,431
Real estate assets held for sale included in net real estate assets	$	13,032		$	10,276

As of December 31, 2018, the Company had one operating store and one parcel of land classified as held for sale. The estimated fair value less selling costs of these assets are greater than the carrying value of the assets, and therefore no loss has been recorded related to these assets. These assets held for sale are included in the self-storage operations segment of the Company’s segment information.

The Company amortizes to expense intangible assets—tenant relationships on a straight-line basis over the average period that a tenant is expected to utilize the facility (currently estimated at 18 months). The Company amortizes to expense the intangible lease rights over the terms of the related leases. Amortization related to the tenant relationships and lease rights was $9,050, $14,349, and $21,133 for the years ended December 31, 2018, 2017 and 2016, respectively. The remaining balance of the unamortized lease rights will be amortized over the next one year to 43 years. Accumulated amortization related to intangibles was $121,238 and $112,347 as of December 31, 2018 and 2017, respectively.

Property Acquisitions and Dispositions

12 Months Ended

Dec. 31, 2018

Real Estate [Abstract]

Property Acquisitions and Dispositions

PROPERTY ACQUISITIONS AND DISPOSITIONS

The following table shows the Company’s acquisitions of stores for the years ended December 31, 2018 and 2017. The table excludes purchases of raw land or improvements made to existing assets.



			Consideration Paid																		Total
Quarter	Number of Stores		Total		Cash Paid		Loan Assumed		Non- controlling interests			Investments in Real Estate Ventures			Net Liabilities/ (Assets) Assumed			Value of OP Units Issued		Number of OP Units Issued	Real estate assets
Q4 2018	6		$	74,852	$	74,868	$	—	$	—		$	—		$	(16	)	$	—	—	$	74,852
Q3 2018	6		74,694		71,989		—		—			—			2,705			—		—	74,694
Q2 2018	17		237,284		148,650		87,500		—			(1,024		)	281			1,877		21,768	237,284
Q1 2018	5		70,787		70,171		—		—			489			127			—		—	70,787
	34	⁽¹⁾	$	457,617	$	365,678	$	87,500	$	—		$	(535	)	$	3,097		$	1,877	21,768	$	457,617

Q4 2017	37		$	535,299	$	502,845	$	14,592	$	(1,812	)	$	12,957		$	1,099		$	5,618	64,708	$	535,299
Q3 2017	4		31,966		29,919		—		—			—			47			2,000		25,520	31,966
Q2 2017	3		34,641		16,608		9,463		1,827			—			(67		)	6,810		272,400	34,641
Q1 2017	2		25,556		25,541		—		—			—			15			—		—	25,556
	46	⁽²⁾	$	627,462	$	574,913	$	24,055	$	15		$	12,957		$	1,094		$	14,428	362,628	$	627,462


(1)	Store acquisitions during the year ended December 31, 2018 include the acquisition of 15 stores previously held in joint ventures where the Company held a noncontrolling interest. The Company purchased its partners' remaining equity interests in the joint ventures, and the properties owned by the joint ventures became wholly owned by the Company.


(2)	Store acquisitions during the year ended December 31, 2017 include the acquisition of seven stores that had been owned by joint ventures in which the Company held an equity interest.

Store Disposals

On August 16, 2018, the Company sold a store located in California that had been classified as held for sale for $40,235 in cash. The Company recorded a gain on the sale of $30,671.

On November 30, 2017, the Company sold 36 stores located in various states that had been classified as held for sale for an aggregate sales price of $295,000. The buyer of these properties was Storage Portfolio II JV, LLC ("SP II"), a newly formed joint venture in which the Company has a 10.0% equity interest. The Company recognized a gain of $118,776 related to this disposition, which represented 90.0% of the total gain. This amount is included in Gain on real estate transactions, earnout on prior acquisitions and impairment of real estate on the Company's consolidated statements of operations. The Company deferred 10.0% of the gain due to the fact that it held an equity interest in the buyer, which resulted in a reduction in the carrying value of the Company's investment in SP II.

On September 13, 2017, the Company closed on the sale of a parcel of land located in New York that had been classified as held for sale for $19,000 in cash. This parcel of land had been written down to its fair value less selling costs during the six months ended June 30, 2017, and a loss of $3,500 was recorded. Therefore, no additional gain or loss was recorded related to this sale at the time of closing.

On July 26, 2016, the Company completed the sale of an operating store located in Indiana that had been classified as held for sale for $4,447 in cash. The Company recognized no gain or loss related to this disposition.

On April 20, 2016, the Company completed the sale of seven operating stores located in Ohio and Indiana that had been classified as held for sale for $17,555 in cash. The Company recognized a gain of $11,265 related to this disposition, which is included in Gain on real estate transactions, earnout on prior acquisitions and impairment of real estate on the Company's consolidated statements of operations.

On April 1, 2016, the Company disposed of a single store in Texas in exchange for 85,452 of the Company's OP Units valued at $7,689. The Operating Partnership canceled the OP Units received in this disposition. The Company recognized a gain of $93 related to this disposition, which is included in Gain on real estate transactions, earnout on prior acquisitions and impairment of real estate on the Company's consolidated statements of operations.

Loss on Earnouts from Prior Acquisitions

On December 2014, the Company acquired a portfolio of five stores located in New Jersey and Virginia. As part of this acquisition, the Company agreed to make an additional cash payment to the sellers if the acquired stores exceeded a specified amount of net operating income for the years ending December 31, 2015 and 2016. At the acquisition date, the Company recorded an estimated liability related to this earnout provision. The operating income of these stores during the earnout period was higher than expected, resulting in an increase in the estimate of the amount due to the sellers of $4,284, which was recorded as a loss and included in Gain on real estate transactions, earnout on prior acquisitions and impairment of real estate on the Company's consolidated statements of operations for the year ended December 31, 2016.

Investments in Unconsolidated Real Estate Ventures

12 Months Ended

Dec. 31, 2018

Equity Method Investments and Joint Ventures [Abstract]

Investments in Unconsolidated Real Estate Ventures

INVESTMENTS IN UNCONSOLIDATED REAL ESTATE VENTURES

Investments in unconsolidated real estate ventures and cash distributions in unconsolidated real estate ventures consist of the following:



	Number of Stores	Equity Ownership %	Excess Profit %	December 31,
	Number of Stores	Equity Ownership %	Excess Profit %	2018			2017
WICNN JV LLC	7	10%	25%	$	26,885		$	—
VRS Self Storage, LLC	16	45%	54%	18,281			19,467
PRISA Self Storage LLC	85	4%	4%	9,334			9,638
Alan Jathoo JV LLC	9	10%	10%	8,180			—
Extra Space West Two LLC ⁽¹⁾	5	5%	40%	3,818			3,939
ESS Bristol Investments LLC	7	10%	28%	2,331			1,258
WCOT Self Storage LLC	—	5%	20%	—			(357		)
Extra Space West One LLC ⁽¹⁾	7	5%	40%	(1,038		)	(900		)
Extra Space Northern Properties Six LLC	10	10%	35%	(1,700		)	(1,279		)
Storage Portfolio II JV LLC	36	10%	30%	(4,233		)	(3,140		)
Storage Portfolio I LLC	24	34%	49%	(38,129		)	11,495
Other minority owned stores (17 joint ventures)	23	10-50%	19-50%	56,400			29,970
Net Investments in and Cash distributions in unconsolidated real estate ventures	229			$	80,129		$	70,091


(1)	Subsequent to year end, the Company acquired its joint venture partner's interests in Extra Space West One LLC and Extra Space West Two LLC joint ventures. The 12 stores owned by these joint ventures became wholly-owned by the Company subsequent to this acquisition. The Company paid cash of $172,515 and assumed an existing loan of $17,157.

In these joint ventures, the Company and the joint venture partner generally receive a preferred return on their invested capital. To the extent that cash or profits in excess of these preferred returns are generated through operations or capital transactions, the Company would receive a higher percentage of the excess cash or profits, as applicable, than its equity interest.

In accordance with ASC 810, the Company reviews all of its joint venture relationships annually to ensure that there are no entities that require consolidation. As of December 31, 2018, there were no previously unconsolidated entities that were required to be consolidated as a result of this review.

The Company has entered into several new unconsolidated real estate ventures. The Company accounts for its investment in the following ventures under the equity method of accounting. Information about these real estate ventures is summarized as follows:



	Number of Stores	Equity ownership %	Investment in new stores
For the Year Ended December 31, 2018⁽¹⁾	28	10.0% -50.0%	$	63,723
For the Year Ended December 31, 2017	39	10.0% - 25.0%	$	13,341
For the Year Ended December 31, 2016	8	20.0% - 50.0%	$	26,387


(1)	Included in the new unconsolidated joint ventures for the year ended December 31, 2018 were two new joint ventures (WICNN JV LLC and GFV JV, LLC), in which the Company has $22,734 and $8,720 of preferred equity, respectively. The Company earns an 8.0% return on its preferred equity in these joint ventures, which has priority over other distributions.

On April 30, 2018, the Company acquired its partner's interest in the WCOT Self Storage LLC joint venture. The Company paid cash of $115,797 and assumed a loan of $87,500. The 14 properties owned by this joint venture became wholly-owned properties of the Company subsequent to this acquisition.

On November 17, 2016, the Company acquired 11 stores from its ESS WCOT LLC joint venture ("WCOT") in a step acquisition. The Company owned 5.0% of WCOT, with the other 95.0% owned by affiliates of Prudential Global Investment Management ("Prudential"). WCOT created a new subsidiary, Extra Space Properties 132 LLC ("ESP 132") and transferred 11 stores into ESP 132. WCOT then distributed ESP 132 to the Company and Prudential on a pro rata basis. This distribution was accounted for as a spinoff, and was therefore recorded at the net carrying amount of the properties of $68,814. Immediately after the distribution, the Company acquired Prudential's 95.0% interest in ESP 132 for $153,304, resulting in 100% ownership of ESP 132 and the related 11 stores. Based on the purchase price of Prudential's share of ESP 132, the Company determined that the fair value of its investment in ESP 132 immediately prior to the acquisition of Prudential's share was $8,119, and the Company recorded a gain of $4,651 as a result of remeasuring to fair value its existing equity interest in ESP 132. This gain is included in equity in earnings of unconsolidated real estate ventures - gain on sale of real estate assets and purchase of joint venture partners' interests on the Company's consolidated statements of operations. The fair value of the stores purchased was recorded at $161,072.

On September 16, 2016, the Company acquired 23 stores from its ESS PRISA II LLC joint venture ("PRISA II") in a step acquisition. The Company owned 4.4% of PRISA II, with the other 95.6% owned by affiliates of Prudential. PRISA II created a new subsidiary, Extra Space Properties 131 LLC ("ESP 131"), and transferred 23 stores into ESP 131. PRISA II then distributed ESP 131 to the Company and Prudential on a pro rata basis. This distribution was accounted for as a spinoff, and was therefore recorded at the net carrying amount of the properties of $4,326. Immediately after the distribution, the Company acquired Prudential's 95.6% interest in ESP 131 for $238,679, resulting in 100% ownership of ESP 131 and the related 23 stores. Based on the purchase price of Prudential's share of ESP 131, the Company determined that the fair value of its investment in ESP 131 immediately prior to the acquisition of Prudential's share was $10,988, and the Company recorded a gain of $6,778 as a result of re-measuring to fair value its existing equity interest in ESP 131. This gain is included in equity in earnings of unconsolidated real estate ventures - gain on sale of real estate assets and purchase of joint venture partners' interests on the Company's consolidated statements of operations. The fair value of the stores purchased was recorded at $248,530. Subsequent to these transactions, PRISA II owned 42 stores.

On September 16, 2016, subsequent to its acquisition of 23 properties as outlined above, the Company sold its 4.42% interest in PRISA II to Prudential for $34,758 in cash. The carrying value of the Company's investment prior to the acquisition was $3,912, and the Company recorded a gain on the sale of $30,846. This gain is included in equity in earnings of unconsolidated real estate ventures - gain on sale of real estate assets and purchase of joint venture partners' interests on the Company's consolidated statements of operations.

On April 25, 2016, the Company and Prudential entered into the “Second Amendment to Amended and Restated Operating Agreement of ESS PRISA LLC” and the “First Amendment to Amended and Restated Operating Agreement of ESS PRISA II LLC” (the “Amendments”). The Amendments are deemed effective as of April 1, 2016. Under the Amendments, the Company gave up any future rights to receive distributions from these joint ventures at the higher “excess profit participation” percentage of 17.0% in exchange for a higher equity ownership percentage. The Company’s equity ownership in ESS PRISA LLC increased from 2.0% to 4.0%, and the Company’s equity ownership in ESS PRISA II LLC increased from 2.0% to 4.4%. The Company continues to account for its investment in PRISA under the equity method of accounting. The Company subsequently sold its interest in PRISA II as noted above.

On February 2, 2016, the Company acquired six stores from its VRS Self Storage LLC joint venture (“VRS”) in a step acquisition. The Company owns 45.0% of VRS, with the other 55.0% owned by affiliates of Prudential. VRS created a new subsidiary, Extra Space Properties 122 LLC (“ESP 122”) and transferred six stores into ESP 122. VRS then distributed ESP 122 to the Company and Prudential on a pro rata basis. This distribution was accounted for as a spinoff, and was therefore recorded at the net carrying amount of the properties of $17,261. Immediately after the distribution, the Company acquired Prudential’s 55.0% interest in ESP 122 for $53,940, resulting in 100% ownership of ESP 122 and the related six stores. Based on the purchase price of Prudential’s share of ESP 122, the Company determined that the fair value of its investment in ESP 122 immediately prior to the acquisition of Prudential’s share was $44,184, and the Company recorded a gain of $26,923 as a result of re-measuring to fair value its existing equity interest in ESP 122. This gain is included in equity in earnings of unconsolidated real estate ventures - gain on sale of real estate assets and purchase of joint venture partners’ interests on the Company’s consolidated statements of operations. The fair value of the stores purchased was recorded at $98,082.

Equity in earnings of unconsolidated real estate ventures consists of the following:



	For the Year Ended December 31,
	2018			2017		2016
Equity in earnings of WICNN JV LLC	$	622		$	—	$	—
Equity in earnings of VRS Self Storage, LLC	3,640			3,562		2,919
Equity in earnings of PRISA Self Storage LLC	2,338			2,430		1,912
Equity in earnings of Alan Jathoo JV LLC	(12		)	—		—
Equity in earnings of Extra Space West Two LLC	1,042			1,210		174
Equity in earnings of ESS Bristol Investments LLC	(152		)	—		—
Equity in earnings of Extra Space West One LLC	2,526			2,502		2,269
Equity in earnings of WCOT Self Storage LLC	359			1,033		614
Equity in earnings of Extra Space Northern Properties Six LLC	1,014			918		823
Equity in earnings of Storage Portfolio I LLC	1,886			2,684		2,380
Equity in earnings of Storage Portfolio II JV LLC	79			33		—
Equity in earnings of other minority owned stores	1,110			959		1,804
	$	14,452		$	15,331	$	12,895

Equity in earnings of certain of our joint ventures includes the amortization of the Company’s excess purchase price of $27,867 of these equity investments over its original basis. The excess basis is amortized over 40 years.

Notes Payable and Revolving Lines of Credit

12 Months Ended

Dec. 31, 2018

Debt Disclosure [Abstract]

Notes Payable and Revolving Lines of Credit

NOTES PAYABLE AND REVOLVING LINES OF CREDIT

The components of notes payable are summarized as follows:



Notes Payable	December 31, 2018			December 31, 2017			Fixed Rate	Variable Rate	Basis Rate ⁽²⁾	Maturity Dates
Secured fixed rate notes payable ⁽¹⁾	$	2,032,414		$	2,095,495		2.5% - 6.0%			February 2019 - February 2030
Secured variable rate notes payable ⁽¹⁾	834,735			717,979				3.9% - 4.1%	Libor plus 1.4% - 1.6%	May 2019 - August 2028
Unsecured fixed rate notes payable	990,000			600,000			3.4% - 4.4%			January 2024 - July 2028
Unsecured variable rate notes payable	310,000			350,000				3.8%	Libor plus 1.3%	October 2023 - January 2024
Total	4,167,149			3,763,474
Less: unamortized debt issuance costs	(29,936		)	(24,977		)
Total	$	4,137,213		$	3,738,497

⁽¹⁾ The loans are collateralized by mortgages on real estate assets and the assignment of rents.
⁽²⁾ 30-day USD LIBOR

On December 7, 2018, the Company amended the credit agreement originally entered into on October 14, 2016 (the "Credit Agreement"). The amended Credit Agreement provides for aggregate borrowings of up to $1.35 billion consisting of a senior unsecured four-year revolving credit facility of $650 million maturing January 2023 (the “Revolving Credit Facility”), a senior unsecured loan of $480 million maturing January 2024 (the Tranche 1 Term Loan Facility”) and a senior unsecured loan of $220 million maturing October 2023 (the “Tranche 2 Term Loan Facility” and, together with the Revolving Credit Facility and the Tranche 1 Term Loan Facility, the “Credit Facility”). The Company may request an increase in the amount of the commitments under the Credit Facility up to an aggregate of $2.0 billion, and extend the term of the Revolving Credit Facility for up to two additional periods of six months each, after satisfying certain conditions.

Amounts outstanding under the Credit Facility bear interest at floating rates, at the Company’s option, equal to either (i) LIBOR plus the applicable Eurodollar rate margin or (ii) the applicable base rate which is the applicable margin plus the highest of (a) 0.0%, (b) the federal funds rate plus 0.50%, (c) U.S. Bank’s prime rate or (d) the Eurodollar rate plus 1.00%. The applicable Eurodollar rate margin will range from 1.05% to 1.7% per annum and the applicable base rate margin will range from 0.05% to 0.7% per annum, in each case depending on the Company’s Consolidated Leverage Ratio, as defined in the Credit Agreement, and the type of loan. If the Operating Partnership obtains a specified investment grade rating from two or more specified credit rating agencies, and elects to use the alternative rates based on the Company’s debt rating, the applicable Eurodollar rate margin will range from 0.75% to 1.65% per annum and the applicable base rate margin will range from 0.0% to 0.7% per annum, in each case depending on the rating achieved and the type of loan.

The Credit Agreement is guaranteed by the Company and is not secured by any assets of the Company. We are subject to certain restrictive covenants relating to our outstanding debt. As of December 31, 2018, the Company was in compliance with all of its financial covenants.

The following table summarizes the scheduled maturities of notes payable, excluding available extensions, at December 31, 2018:




2019	$	208,742
2020	699,522
2021	228,015
2022	294,948
2023	915,646
Thereafter	1,820,276
	$	4,167,149

Real estate assets are pledged as collateral for the secured loans. Of the Company’s $4,167,149 principal amount of notes payable outstanding at December 31, 2018, $2,601,960 was recourse due to guarantees or other security provisions.

All of the Company’s lines of credit are guaranteed by the Company. The following table presents information on the Company’s lines of credit, the proceeds of which are used to repay debt and for general corporate purposes, for the periods indicated:

As of December 31, 2018

Revolving Lines of Credit

Amount Drawn

Capacity

Interest Rate

Origination Date

Maturity

Basis Rate ⁽¹⁾

Credit Line 1 ⁽²⁾

81,000

140,000

4.0%

6/4/2010

7/1/2021

LIBOR plus 1.5%

Credit Line 2 ⁽³⁾⁽⁴⁾

—

650,000

3.6%

12/7/2018

1/29/2023

LIBOR plus 1.1%

81,000

790,000

(1) 30-day USD LIBOR

(2) Secured by mortgages on certain real estate assets. One two-year extension available.

(3) Unsecured. Two six-month extensions available.

(4) Basis Rate as of December 31, 2018. Rate is subject to change based on our consolidated leverage ratio.

EXCHANGEABLE SENIOR NOTES

In September 2015, the Operating Partnership issued $575,000 of its 3.125% Exchangeable Senior Notes due 2035. Costs incurred to issue the 2015 Notes were approximately $11,992, consisting primarily of a 2.0% underwriting fee. These costs are being amortized as an adjustment to interest expense over five years, which represents the estimated term based on the first available redemption date, and are included in exchangeable senior notes, net, in the consolidated balance sheets. The 2015 Notes are general unsecured senior obligations of the Operating Partnership and are fully guaranteed by the Company. Interest is payable on April 1 and October 1 of each year beginning April 1, 2016, until the maturity date of October 1, 2035. The Notes bear interest at 3.125% per annum and contain an exchange settlement feature, which provides that the 2015 Notes may, under certain circumstances, be exchangeable for cash (for the principal amount of the 2015 Notes) and, with respect to any excess exchange value, for cash, shares of the Company’s common stock, or a combination of cash and shares of the Company’s common stock, at the Company’s option. The exchange rate of the 2015 Notes as of December 31, 2018 was approximately 10.78 shares of the Company’s common stock per $1,000 principal amount of the 2015 Notes.

The Operating Partnership may redeem the 2015 Notes at any time to preserve the Company’s status as a REIT. In addition, on or after October 5, 2020, the Operating Partnership may redeem the 2015 Notes for cash, in whole or in part, at 100% of the principal amount plus accrued and unpaid interest, upon at least 30 days but not more than 60 days prior written notice to the holders of the 2015 Notes. The holders of the 2015 Notes have the right to require the Operating Partnership to repurchase the 2015 Notes for cash, in whole or in part, on October 1 of the years 2020, 2025 and 2030, (unless the Operating Partnership has called the 2015 Notes for redemption), and upon the occurrence of certain designated events, in each case for a repurchase price equal to 100% of the principal amount of the 2015 Notes plus accrued and unpaid interest. Certain events are considered “Events of Default,” as defined in the indenture governing the 2015 Notes, which may result in the accelerated maturity of the 2015 Notes.

Additionally, the 2015 Notes can be exchanged during any calendar quarter, if the last reported sale price of the common stock of the Company is greater than or equal to 130% of the exchange price for at least 20 trading days during a period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter. The price of the Company’s common stock did not exceed 130% of the exchange price for the required time period for the 2015 Notes during the quarter ended December 31, 2018.

On June 21, 2013, the Operating Partnership issued $250,000 of its 2013 Notes at a 1.5% discount, or $3,750. Costs incurred to issue the 2013 Notes were approximately $1,672. These costs were amortized as an adjustment to interest expense over five years, which represented the estimated term based on the first available redemption date. The 2013 Notes bore interest at 2.375% per annum and contained an exchange settlement feature. The Operating Partnership redeemed all remaining outstanding 2013 Notes on July 5, 2018.

GAAP requires entities with convertible debt instruments that may be settled entirely or partially in cash upon conversion to separately account for the liability and equity components of the instrument in a manner that reflects the issuer’s economic interest cost. The Company therefore accounts for the liability and equity component of the 2015 Notes separately. The equity components are included in paid-in capital in stockholders’ equity in the consolidated balance sheets, and the value of the equity components are treated as original issue discount for purposes of accounting for the debt components. The discount is being amortized as interest expense over the remaining period of the debt through its first redemption date, October 1, 2020 for the 2015 Notes. The effective interest rate on the liability components of the 2015 Notes is 4.0%, which approximates the market rate of interest of similar debt without exchange features (i.e. nonconvertible debt) at the time of issuance.

Information about the 2013 Notes and 2015 Notes (collectively, the "Notes"), including the total carrying amounts of the equity components, the principal amounts of the liability components, their unamortized discounts and net carrying amount were as follows for the periods indicated:



	December 31, 2018			December 31, 2017
Carrying amount of equity component - 2015 Notes	$	22,597		$	22,597
Carrying amount of equity component - 2013 Notes	—			—
Carrying amount of equity components	$	22,597		$	22,597
Principal amount of liability component - 2015 Notes	$	575,000		$	575,000
Principal amount of liability component - 2013 Notes	—			49,259
Unamortized discount - equity component - 2015 Notes	(8,417		)	(12,974		)
Unamortized discount - equity component - 2013 Notes	—			(315		)
Unamortized cash discount - 2013 Notes	—			(74		)
Unamortized debt issuance costs	(4,209		)	(6,620		)
Net carrying amount of liability components	$	562,374		$	604,276

The amount of interest cost recognized relating to the contractual interest rate and the amortization of the discount on the liability component for the Notes were as follows for the periods indicated:



	For the Year Ended December 31,
	2018		2017		2016
Contractual interest	$	18,106	$	19,303	$	19,483
Amortization of discount	4,687		5,103		4,980
Total interest expense recognized	$	22,793	$	24,406	$	24,463

Repurchase of 2013 Notes

During the year ended December 31, 2018, the Company repurchased a total principal amount of $49,259 of the 2013

Notes, which represented all of the remaining principal amount outstanding. The Company paid cash of $80,270 for the total of

the principal amount and the exchange value in excess of the principal amount.

During the year ended December 31, 2017, the Company repurchased a total principal amount of $13,911 of the 2013 Notes. The Company paid cash of $20,042 for the total of the principal amount and the exchange value in excess of the principal amount.

During the year ended December 31, 2016, the Company repurchased a total principal amount of $22,194 of the 2013 Notes. The Company paid cash for the principal amount, and issued a total of 148,940 shares of common stock valued at $13,066 for the exchange value in excess of the principal amount.

The Company allocated the value of the consideration paid to repurchase the 2013 Notes (1) to the extinguishment of the liability component and (2) to the reacquisition of the equity component. The amount allocated to the extinguishment of the liability component is equal to the fair value of that component immediately prior to extinguishment. The difference between the consideration attributed to the extinguishment of the liability component and the sum of (a) the net carrying amount of the repurchased liability component, and (b) the related unamortized debt issuance costs, is recognized as a gain on debt extinguishment. The remaining settlement consideration is allocated to the reacquisition of the equity component of the repurchased 2013 Notes and recognized as a reduction of stockholders’ equity.

Information about the repurchases is as follows:



	For the Year Ended December 31,
	2018			2017			2016
Principal amount repurchased	$	49,259		$	13,911		$	22,194

Amount allocated to:
Extinguishment of liability component	$	49,019		$	13,692		$	21,363
Reacquisition of equity component	31,251			6,350			13,898
Total consideration paid for repurchase	$	80,270		$	20,042		$	35,261
Exchangeable senior notes repurchased	$	49,259		$	13,911		$	22,194
Extinguishment of liability component	(49,019		)	(13,692		)	(21,363		)
Discount on exchangeable senior notes	(230		)	(184		)	(788		)
Related debt issuance costs	(10		)	(35		)	(43		)
Gain/(loss) on repurchase	$	—		$	—		$	—

Derivatives

12 Months Ended

Dec. 31, 2018

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Derivatives

DERIVATIVES

The Company is exposed to certain risk arising from both its business operations and economic conditions. The Company principally manages its exposures to a wide variety of business and operational risks through management of its core business activities. The Company manages economic risks, including interest rate, liquidity, and credit risk primarily by managing the amount, sources and duration of its debt funding and the use of derivative financial instruments. Specifically, the Company enters into derivative financial instruments to manage exposures that arise from business activities that result in the receipt or payment of future known and uncertain cash amounts, the value of which are determined by interest rates. The Company’s derivative financial instruments are used to manage differences in the amount, timing and duration of the Company’s known or expected cash receipts and its known or expected cash payments principally related to the Company’s investments and borrowings.

Cash Flow Hedges of Interest Rate Risk

The Company’s objectives in using interest rate derivatives are to add stability to interest expense and to manage its exposure to interest rate movements. To accomplish this objective, the Company primarily uses interest rate swaps as part of its interest rate risk management strategy. Interest rate swaps designated as cash flow hedges involve the receipt of variable amounts from a counterparty in exchange for the Company making fixed-rate payments over the life of the agreements without exchange of the underlying notional amount.

The effective portion of changes in the fair value of derivatives designated and that qualify as cash flow hedges is recorded in accumulated other comprehensive income (“OCI”) and is subsequently reclassified into earnings in the period that the hedged forecasted transaction affects earnings. A portion of these changes is excluded from accumulated other comprehensive income as it is allocated to noncontrolling interests. During the years ended December 31, 2018, 2017 and 2016, such derivatives were used to hedge the variable cash flows associated with existing variable-rate debt. During 2019, the Company estimates that $17,439 will be reclassified as a decrease to interest expense.

The following table summarizes the terms of the Company’s 28 derivative financial instruments, which have a total combined notional amount of $2,231,162 as of December 31, 2018:



Hedge Product	Range of Notional Amounts	Strike	Effective Dates	Maturity Dates
Swap Agreements	$4,873 - $267,431	1.13% - 3.87%	2/29/2012 - 12/31/2018	2/28/2019 - 7/12/2025

Fair Values of Derivative Instruments

The table below presents the fair value of the Company’s derivative financial instruments as well as their classification on the consolidated balance sheets:



	Asset / Liability Derivatives
	December 31, 2018		December 31, 2017
Derivatives designated as hedging instruments:	Fair Value
Other assets	$	42,324	$	38,365
Other liabilities	$	2,131	$	9

Effect of Derivative Instruments

The tables below present the effect of the Company’s derivative financial instruments on the consolidated statements of operations for the periods presented. No tax effect has been presented as the derivative instruments are held by the Company:



	Gain (loss) recognized in OCI For the Year Ended December 31,				Location of amounts reclassified from OCI into income	Gain (loss) reclassified from OCI For the Year Ended December 31,
Type	2018		2017		Location of amounts reclassified from OCI into income	2018		2017			2016
Swap Agreements	$	9,889	$	8,499	Interest expense	$	8,258	$	(8,853	)	$	(18,800	)

Credit-Risk-Related Contingent Features

The Company has agreements with some of its derivative counterparties that contain provisions pursuant to which, the Company could be declared in default of its derivative obligations if the Company defaults on any of its indebtedness, including default where repayment of the indebtedness has not been accelerated by the lender.

The Company also has an agreement with some of its derivative counterparties that incorporates the loan covenant provisions of the Company’s indebtedness with a lender affiliate of the derivative counterparty. Failure to comply with the loan covenant provisions would result in the Company being in default on any derivative instrument obligations covered by the agreement.

As of December 31, 2018, the fair value of derivatives in a net liability position, which includes accrued interest but excludes any adjustment for nonperformance risk, related to these agreements was $1,785. As of December 31, 2018, the Company had not posted any collateral related to these agreements. If the Company had breached any of these provisions as of December 31, 2018, it could have been required to cash settle its obligations under these agreements at their termination value of $2,422.

Notes Payable to Trusts

12 Months Ended

Dec. 31, 2018

Equity [Abstract]

Notes Payable to Trusts

NOTES PAYABLE TO TRUSTS

During July 2005, ESS Statutory Trust III (the “Trust III”), a newly formed Delaware statutory trust and a wholly-owned, unconsolidated subsidiary of the Operating Partnership, issued an aggregate of $40,000 of preferred securities which mature on July 31, 2035. In addition, Trust III issued 1,238 of Trust common securities to the Operating Partnership for a purchase price of $1,238. On July 27, 2005, the proceeds from the sale of the preferred and common securities of $41,238 were loaned in the form of a note to the Operating Partnership (“Note 3”). Note 3 had a fixed rate of 6.91% through July 31, 2010, and then was payable at a variable rate equal to the three month LIBOR plus 2.4% per annum. Effective July 11, 2011, Trust III entered into an interest rate swap that fixed the interest rate to be paid at 5.0% per annum and matured July 11, 2018. The interest on Note 3, payable quarterly, was be used by Trust III to pay dividends on the trust preferred securities. The trust preferred securities became redeemable by Trust III with no prepayment premium on July 27, 2010.

During May 2005, ESS Statutory Trust II (the “Trust II”), a newly formed Delaware statutory trust and a wholly-owned, unconsolidated subsidiary of the Operating Partnership of the Company, issued an aggregate of $41,000 of preferred securities which mature on June 30, 2035. In addition, Trust II issued 1,269 of Trust common securities to the Operating Partnership for a purchase price of $1,269. On May 24, 2005, the proceeds from the sale of the preferred and common securities of $42,269 were loaned in the form of a note to the Operating Partnership (“Note 2”). Note 2 had a fixed rate of 6.7% through June 30, 2010, and then was payable at a variable rate equal to the three month LIBOR plus 2.4% per annum. Effective July 11, 2011, Trust II entered into an interest rate swap that fixed the interest rate to be paid at 5.0% per annum and matured July 11, 2018. The interest on Note 2, payable quarterly, was be used by Trust II to pay dividends on the trust preferred securities. The trust preferred securities became redeemable by Trust II with no prepayment premium on June 30, 2010.

During April 2005, ESS Statutory Trust I (the “Trust”), a newly formed Delaware statutory trust and a wholly-owned, unconsolidated subsidiary of the Operating Partnership of the Company issued an aggregate of $35,000 of trust preferred securities which mature on June 30, 2035. In addition, Trust issued 1,083 of Trust common securities to the Operating Partnership for a purchase price of $1,083. On April 8, 2005, the proceeds from the sale of the trust preferred and common securities of $36,083 were loaned in the form of a note to the Operating Partnership (the “Note”). The Note has a variable rate equal to the three month LIBOR plus 2.3% per annum. Effective June 30, 2010, Trust entered into an interest rate swap that fixed the interest rate to be paid at 5.1% per annum and matured on June 30, 2018. The interest on the Note, payable quarterly, will be used by Trust to pay dividends on the trust preferred securities. The trust preferred securities are redeemable by Trust with no prepayment premium.

Trust, Trust II and Trust III (together, the “Trusts”) are VIEs because the holders of the equity investment at risk (the trust preferred securities) do not have the power to direct the activities of the entities that most significantly affect the entities’ economic performance because of their lack of voting or similar rights. Because the Operating Partnership’s investment in the Trusts’ common securities was financed directly by the Trusts as a result of its loan of the proceeds to the Operating Partnership, that investment is not considered to be an equity investment at risk. The Operating Partnership’s investment in the Trusts is not a variable interest because equity interests are variable interests only to the extent that the investment is considered to be at risk, and therefore the Operating Partnership cannot be the primary beneficiary of the Trusts. Since the Company is not the primary beneficiary of the Trusts, they have not been consolidated. A debt obligation has been recorded in the form of notes as discussed above for the proceeds, which are owed to the Trusts by the Company. The Company has also recorded its investment in the Trusts’ common securities as other assets.

During the year ended December 31, 2018, the Company repaid a total principal amount of $88,662, representing all of the notes payable to Trust III, all of the notes payable to Trust II, and all but $30,928 of the notes payable to Trust. The Trusts used the proceeds from these repayments to redeem their preferred and common securities.

The Company has not provided financing or other support during the periods presented to the Trusts that it was not previously contractually obligated to provide. The Company’s maximum exposure to loss as a result of its involvement with the Trusts is equal to the total amount of the notes discussed above less the amounts of the Company’s investments in the Trusts’ common securities. The net amount is the notes payable that the Trusts owe to third parties for their investments in the Trusts’ preferred securities.

The notes payable to trusts are presented net of unamortized deferred financing costs of $0 and $2,146 as of December 31, 2018 and 2017, respectively.

Following is a tabular comparison of the liabilities the Company has recorded as a result of its involvements with the Trusts to the maximum exposure to loss the Company is subject to related to the Trusts as of December 31, 2018:



	Notes payable to Trusts		Investment Balance		Maximum exposure to loss		Difference
Trust	$	30,928	$	928	$	30,000	$	—

Exchangeable Senior Notes

12 Months Ended

Dec. 31, 2018

Debt Disclosure [Abstract]

Exchangeable Senior Notes

NOTES PAYABLE AND REVOLVING LINES OF CREDIT

The components of notes payable are summarized as follows:



Notes Payable	December 31, 2018			December 31, 2017			Fixed Rate	Variable Rate	Basis Rate ⁽²⁾	Maturity Dates
Secured fixed rate notes payable ⁽¹⁾	$	2,032,414		$	2,095,495		2.5% - 6.0%			February 2019 - February 2030
Secured variable rate notes payable ⁽¹⁾	834,735			717,979				3.9% - 4.1%	Libor plus 1.4% - 1.6%	May 2019 - August 2028
Unsecured fixed rate notes payable	990,000			600,000			3.4% - 4.4%			January 2024 - July 2028
Unsecured variable rate notes payable	310,000			350,000				3.8%	Libor plus 1.3%	October 2023 - January 2024
Total	4,167,149			3,763,474
Less: unamortized debt issuance costs	(29,936		)	(24,977		)
Total	$	4,137,213		$	3,738,497

⁽¹⁾ The loans are collateralized by mortgages on real estate assets and the assignment of rents.
⁽²⁾ 30-day USD LIBOR

The following table summarizes the scheduled maturities of notes payable, excluding available extensions, at December 31, 2018:




2019	$	208,742
2020	699,522
2021	228,015
2022	294,948
2023	915,646
Thereafter	1,820,276
	$	4,167,149

As of December 31, 2018

Revolving Lines of Credit

Amount Drawn

Capacity

Interest Rate

Origination Date

Maturity

Basis Rate ⁽¹⁾

Credit Line 1 ⁽²⁾

81,000

140,000

4.0%

6/4/2010

7/1/2021

LIBOR plus 1.5%

Credit Line 2 ⁽³⁾⁽⁴⁾

—

650,000

3.6%

12/7/2018

1/29/2023

LIBOR plus 1.1%

81,000

790,000

(1) 30-day USD LIBOR

(2) Secured by mortgages on certain real estate assets. One two-year extension available.

(3) Unsecured. Two six-month extensions available.

(4) Basis Rate as of December 31, 2018. Rate is subject to change based on our consolidated leverage ratio.

EXCHANGEABLE SENIOR NOTES



	December 31, 2018			December 31, 2017
Carrying amount of equity component - 2015 Notes	$	22,597		$	22,597
Carrying amount of equity component - 2013 Notes	—			—
Carrying amount of equity components	$	22,597		$	22,597
Principal amount of liability component - 2015 Notes	$	575,000		$	575,000
Principal amount of liability component - 2013 Notes	—			49,259
Unamortized discount - equity component - 2015 Notes	(8,417		)	(12,974		)
Unamortized discount - equity component - 2013 Notes	—			(315		)
Unamortized cash discount - 2013 Notes	—			(74		)
Unamortized debt issuance costs	(4,209		)	(6,620		)
Net carrying amount of liability components	$	562,374		$	604,276



	For the Year Ended December 31,
	2018		2017		2016
Contractual interest	$	18,106	$	19,303	$	19,483
Amortization of discount	4,687		5,103		4,980
Total interest expense recognized	$	22,793	$	24,406	$	24,463

Repurchase of 2013 Notes

During the year ended December 31, 2018, the Company repurchased a total principal amount of $49,259 of the 2013

Notes, which represented all of the remaining principal amount outstanding. The Company paid cash of $80,270 for the total of

the principal amount and the exchange value in excess of the principal amount.

Information about the repurchases is as follows:



	For the Year Ended December 31,
	2018			2017			2016
Principal amount repurchased	$	49,259		$	13,911		$	22,194

Amount allocated to:
Extinguishment of liability component	$	49,019		$	13,692		$	21,363
Reacquisition of equity component	31,251			6,350			13,898
Total consideration paid for repurchase	$	80,270		$	20,042		$	35,261
Exchangeable senior notes repurchased	$	49,259		$	13,911		$	22,194
Extinguishment of liability component	(49,019		)	(13,692		)	(21,363		)
Discount on exchangeable senior notes	(230		)	(184		)	(788		)
Related debt issuance costs	(10		)	(35		)	(43		)
Gain/(loss) on repurchase	$	—		$	—		$	—

Related Party and Affiliated Real Estate Joint Venture Transactions	12 Months Ended
	Dec. 31, 2018
Related Party Transactions [Abstract]
Related Party and Affiliated Real Estate Joint Venture Transactions	RELATED PARTY AND AFFILIATED REAL ESTATE JOINT VENTURE TRANSACTIONS The Company provides management services to certain joint ventures for a fee. Management fee revenues for related party and affiliated real estate joint ventures for the years ended December 31, 2018, 2017 and 2016 were $14,123, $12,650 and $16,066, respectively.

Stockholders' Equity	12 Months Ended
Stockholders' Equity	Dec. 31, 2018
Equity [Abstract]
Stockholders' Equity	STOCKHOLDERS’ EQUITY The Company’s charter provides that it can issue up to 500,000,000 shares of common stock, $0.01 par value per share and 50,000,000 shares of preferred stock, $0.01 par value per share. As of December 31, 2018, 127,103,750 shares of common stock were issued and outstanding, and no shares of preferred stock were issued or outstanding. All holders of the Company's common stock are entitled to receive dividends and to one vote on all matters submitted to a vote of stockholders. The transfer agent and registrar for the Company’s common stock is American Stock Transfer & Trust Company. On August 28, 2015, the Company filed a $400,000 “at the market” equity program with the Securities and Exchange Commission, and entered into separate equity distribution agreements with five sales agents. On May 6, 2016, the Company filed its current $400,000 "at the market" equity program with the Securities and Exchange Commission using a new shelf registration statement on Form S-3, and entered into separate equity distribution agreements with five sales agents. Under the terms of the current equity distribution agreements, the Company may from time to time offer and sell shares of common stock, up to the aggregate offering price of $400,000, through its sales agents. The current equity distribution agreements, dated May 6, 2016, replaced and superseded the previous equity distribution agreements, dated August 28, 2015. During the year ended December 31, 2018, the Company sold 933,789 shares of common stock under its "at the market" equity program at an average sales price of $97.93 per share, resulting in net proceeds of $90,531. At December 31, 2018, the Company had $257,929 available for issuance under the current equity distribution agreements. During July 2016, the Company sold 550,000 shares of common stock under the current “at the market” equity program at an average sales price of $92.04 per share, resulting in net proceeds of $50,062. From January 1, 2016, through May 6, 2016, the Company sold 831,300 shares of common stock under the previous “at the market” equity program at an average sales price of $89.66 per share, resulting in net proceeds of $73,360.

Noncontrolling Interest Represented By Preferred Operating Partnership Units

12 Months Ended

Dec. 31, 2018

Noncontrolling Interest [Abstract]

Noncontrolling Interest Represented By Preferred Operating Partnership Units

NONCONTROLLING INTEREST REPRESENTED BY PREFERRED OPERATING PARTNERSHIP UNITS

Classification of Noncontrolling Interests

GAAP requires a company to present ownership interests in subsidiaries held by parties other than the company in the consolidated financial statements within the equity section, but separate from the company’s equity. It also requires the amount of consolidated net income attributable to the parent and to the noncontrolling interest to be clearly identified and presented on the face of the consolidated statement of operations and requires changes in ownership interest to be accounted for similarly as equity transactions. If noncontrolling interests are determined to be redeemable, they are to be carried at their redemption value as of the balance sheet date and reported as temporary equity.

The Company has evaluated the terms of the Operating Partnership’s preferred units and classifies the noncontrolling interest represented by such preferred units as stockholders’ equity in the accompanying consolidated balance sheets. The Company will periodically evaluate individual noncontrolling interests for the ability to continue to recognize the noncontrolling amount as permanent equity in the consolidated balance sheets. Any noncontrolling interests that fail to qualify as permanent equity will be reclassified as temporary equity and adjusted to the greater of (1) the carrying amount, or (2) its redemption value as of the end of the period in which the determination is made.

At December 31, 2018 and 2017, the noncontrolling interests represented by the Preferred OP Units qualified for classification as permanent equity on the Company's consolidated balance sheets. The partnership agreement of the Operating Partnership (as amended, the "Partnership Agreement") provides for the designation and issuance of the OP Units. Noncontrolling interests in Preferred OP Units were presented net of notes receivable from preferred Operating Partnership unit holders of $108,644 and $120,230 as of December 31, 2018 and 2017, respectively, as more fully described below.

Series A Participating Redeemable Preferred Units

The Series A Units were issued in June 2007. Series A Units in the amount of $101,700 bear a fixed priority return of 2.3%, and originally had a fixed liquidation value of $115,000. The remaining balance participates in distributions with, and has a liquidation value equal to, that of the common OP Units. The Series A Units became redeemable at the option of the holder on September 1, 2008, which redemption obligation may be satisfied, at the Company’s option, in cash or shares of its common stock. As a result of the redemption of 114,500 Series A Units in October 2014, the remaining fixed liquidation value was reduced to $101,700 which represents 875,480 Series A Units. On April 18, 2017, the holder of the Series A Units and the Operating Partnership agreed to reduce the fixed priority return on the Series A Units from 5.0% to 2.3% in exchange for a reduction in the interest rate of the related loan, as more fully described below.

The Partnership Agreement provides for the designation and issuance of the Series A Units. The Series A Units have priority over all other partnership interests of the Operating Partnership with respect to distributions and liquidation.

On June 25, 2007, the Operating Partnership loaned the holders of the Series A Units $100,000. The note receivable bears interest at 2.1%. On April 18, 2017, a loan amendment was signed modifying the maturity date of the loan to the later of the death of the Series A Unit holder or his spouse and also lowering the interest rate of the loan from 4.9% to 2.1%. The loan amendment was determined to be a loan modification under GAAP, and therefore no change in value was recognized. The loan is secured by the borrower’s Series A Units. No future redemption of Series A Units can be made unless the loan secured by the Series A Units is also repaid. The Series A Units are shown on the balance sheet net of the $100,000 loan because the borrower under the loan is also the holder of the Series A Units.

Series B Redeemable Preferred Units

The Partnership Agreement provides for the designation and issuance of the Series B Units. The Series B Units rank junior to the Series A Units, on parity with the Series C Units and Series D Units, and senior to all other partnership interests of the Operating Partnership with respect to distributions and liquidation.

The Series B Units were issued in 2013 and 2014 and have a liquidation value of $25.00 per unit for a current fixed liquidation value of $41,902 which represents 1,676,087 Series B Units. Holders of the Series B Units receive distributions at an annual rate of 6.0%. These distributions are cumulative. The Series B Units are redeemable at the option of the holder on the first anniversary of the date of issuance, which redemption obligations may be satisfied at the Company’s option in cash or shares of its common stock. The Series B Units rank junior to the Series A Units, on parity with the Series C Units and Series D Units, and senior to all other partnership interests of the Operating Partnership with respect to distributions and liquidation.

Series C Convertible Redeemable Preferred Units

The Partnership Agreement provides for the designation and issuance of the Series C Units. The Series C Units rank junior to the Series A Units, on parity with the Series B Units and Series D Units, and senior to all other partnership interests of the Operating Partnership with respect to distributions and liquidation.

The Series C Units were issued in 2013 and 2014 and have a liquidation value of $42.10 per unit for a current fixed liquidation value of $12,462 which represents 296,020 Series C Units. From issuance to the fifth anniversary of issuance, each Series C Unit holder will receive quarterly distributions equal to the quarterly distribution for common OP Unit plus $0.18. Beginning on the fifth anniversary of issuance, each Series C Unit holder will receive a fixed quarterly distribution equal to the aggregate quarterly distribution payable in respect of such Series C Unit during the four quarters immediately preceding the fifth anniversary of issuance divided by four. These distributions are cumulative. The Series C Units became redeemable at the option of the holder one year from the date of issuance, which redemption obligation may be satisfied at the Company’s option in cash or shares of its common stock. The Series C Units also became convertible into common OP Units at the option of the holder one year from the date of issuance, at a rate of 0.9145 common OP Units per Series C Unit converted. This conversion option expires upon the fifth anniversary of the date of issuance.

In December 2014, the Operating Partnership loaned holders of the Series C Units $20,230. The notes receivable, which are collateralized by the Series C Units, bear interest at 5.0% and mature on December 15, 2024. The Series C Units are shown on the balance sheet net of the loan because the borrower under the loan receivable is also the holder of the Series C Units.

On December 1, 2018, certain holders of the Series C Units converted their Series C Units into common OP Units, with a total of 407,996 Series C Units being converted into a total of 373,113 common OP Units. As part of this conversion, the holders of the Series C Units agreed to pledge the common OP Units received in the conversion as collateral on the loan receivable to replace the Series C Units that were converted. As of December 31, 2018, the total outstanding balance of the loan receivable was $19,735, of which $8,644 is shown as a reduction of the noncontrolling interests related to the Series C Units and $11,091 is shown as a reduction of the noncontrolling interests related to the common OP Units on the Company's consolidated balance sheets.

Series D Redeemable Preferred Units

The Partnership Agreement provides for the designation and issuance of the Series D Units. The Series D Units rank junior to the Series A Units, on parity with the Series B Units and Series C Units, and senior to all other partnership interest of the Operating Partnership with respect to distributions and liquidation.

The Series D Units have been issued at various times from 2014 to 2017. During the year ended December 31, 2017, the Operating Partnership issued 446,420 Series D Units valued at $11,161 in conjunction with wholly-owned and joint venture acquisitions. During the year ended December 31, 2016, the Operating Partnership issued a total of 2,687,711 Series D Units valued at $67,193 in conjunction with the acquisition of real estate assets.

The Series D Units have a liquidation value of $25.00 per unit, for a current fixed liquidation value of $92,064 which represents 3,682,521 Series D Units. Holders of the Series D Units receive distributions at an annual rate between 3.0% and 5.0%. These distributions are cumulative. The Series D Units will become redeemable at the option of the holder on the first anniversary of the date of issuance, which redemption obligation may be satisfied at the Company’s option in cash or shares of its common stock. In addition, certain of the Series D Units are exchangeable for common OP Units until the tenth anniversary of the date of issuance, with the number of common OP Units to be issued equal to $25.00 per Series D Unit, divided by the value of a share of common stock as of the exchange date.

NONCONTROLLING INTEREST IN OPERATING PARTNERSHIP AND OTHER NONCONTROLLING INTERESTS

Noncontrolling interest in Operating Partnership

The Company’s interest in its stores is held through the Operating Partnership. Between its general partner and limited partner interests, the Company held a 91.0% majority ownership interest therein as of December 31, 2018. The remaining ownership interests in the Operating Partnership (including Preferred OP Units) of 9.0% are held by certain former owners of assets acquired by the Operating Partnership.

The noncontrolling interest in the Operating Partnership represents OP Units that are not owned by the Company. OP Units are redeemable at the option of the holder, which redemption may be satisfied at the Company's option in cash based upon the fair market value of an equivalent number of shares of the Company’s common stock (based on the ten-day average trading price) at the time of the redemption. Alternatively, the Company may, at its sole discretion, elect to acquire those OP Units in exchange for shares of its common stock on a one-for-one basis, subject to anti-dilution adjustments provided in the Operating Partnership agreement. The ten-day average closing stock price at December 31, 2018, was $91.64 and there were 5,994,251 OP Units outstanding.

Assuming that all of the OP Unit holders exercised their right to redeem all of their OP Units on December 31, 2018 and the Company elected to pay the OP Unit holders cash, the Company would have paid $549,313 in cash consideration to redeem the units.

OP Unit activity is summarized as follows for the periods presented:



	For the Year Ended December 31,
	2018		2017		2016
OP Units redeemed for common stock	35,000		—		23,850
OP Units redeemed for cash	30,000		33,896		6,760
Cash paid for OP Units redeemed	$	2,558	$	2,510	$	506
OP Units issued in conjunction with acquisitions	21,768		90,228		93,569
Value of OP Units issued in conjunction with acquisitions	$	1,877	$	7,618	$	7,247

Additionally, 373,113 common OP Units were issued in the conversion of 407,996 Series C Units on December 1, 2018. These newly issued OP Units are pledged as collateral on the existing loan receivable to the Series C Unit holders. As a result, noncontrolling interests in the Operating Partnership is reported net of $11,091 of the loan receivable, which represents the portion of the note receivable that is collateralized by the OP Units.

GAAP requires a company to present ownership interests in subsidiaries held by parties other than the company in the consolidated financial statements within the equity section but separate from the company’s equity. It also requires the amount of consolidated net income attributable to the parent and to the noncontrolling interest to be clearly identified and presented on the face of the consolidated statement of operations and requires changes in ownership interest to be accounted for similarly as equity transactions. If noncontrolling interests are determined to be redeemable, they are to be carried at their redemption value as of the balance sheet date and reported as temporary equity.

The Company has evaluated the terms of the common OP Units and classifies the noncontrolling interest represented by the common OP Units as stockholders’ equity in the accompanying consolidated balance sheets. The Company will periodically evaluate individual noncontrolling interests for the ability to continue to recognize the noncontrolling amount as permanent equity in the consolidated balance sheets. Any noncontrolling interests that fail to qualify as permanent equity will be reclassified as temporary equity and adjusted to the greater of (1) the carrying amount, or (2) its redemption value as of the end of the period in which the determination is made.

Noncontrolling Interests In Operating Partnership and Other Noncontrolling Interests

12 Months Ended

Dec. 31, 2018

Noncontrolling Interest [Abstract]

Noncontrolling Interests In Operating Partnership and Other Noncontrolling Interests

NONCONTROLLING INTEREST REPRESENTED BY PREFERRED OPERATING PARTNERSHIP UNITS

Classification of Noncontrolling Interests

Series A Participating Redeemable Preferred Units

Series B Redeemable Preferred Units

Series C Convertible Redeemable Preferred Units

Series D Redeemable Preferred Units

NONCONTROLLING INTEREST IN OPERATING PARTNERSHIP AND OTHER NONCONTROLLING INTERESTS

Noncontrolling interest in Operating Partnership

OP Unit activity is summarized as follows for the periods presented:



	For the Year Ended December 31,
	2018		2017		2016
OP Units redeemed for common stock	35,000		—		23,850
OP Units redeemed for cash	30,000		33,896		6,760
Cash paid for OP Units redeemed	$	2,558	$	2,510	$	506
OP Units issued in conjunction with acquisitions	21,768		90,228		93,569
Value of OP Units issued in conjunction with acquisitions	$	1,877	$	7,618	$	7,247

GAAP requires a company to present ownership interests in subsidiaries held by parties other than the company in the consolidated financial statements within the equity section but separate from the company’s equity. It also requires the amount of consolidated net income attributable to the parent and to the noncontrolling interest to be clearly identified and presented on the face of the consolidated statement of operations and requires changes in ownership interest to be accounted for similarly as equity transactions. If noncontrolling interests are determined to be redeemable, they are to be carried at their redemption value as of the balance sheet date and reported as temporary equity.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock-Based Compensation

STOCK-BASED COMPENSATION

As of December 31, 2018, 1,587,625 shares were available for issuance under the Company’s 2015 Incentive Award Plan (the “Plan”).

Option grants are issued with an exercise price equal to the closing price of stock on the date of grant. Unless otherwise determined by the Compensation, Nominating and Governance Committee (“CNG Committee”) at the time of grant, options shall vest ratably over a four-year period beginning on the date of grant. Each option will be exercisable once it has vested. Options are exercisable at such times and subject to such terms as determined by the CNG Committee, but under no circumstances may be exercised if such exercise would cause a violation of the ownership limit in the Company’s charter. Options expire 10 years from the date of grant. Beginning in 2017, the CNG Committee decided to the replace stock options granted to executives with performance based stock units for executive compensation. See the "Performance-Based Stock Units" section below.

Also as defined under the terms of the Plan, restricted stock grants may be awarded. The stock grants are subject to a vesting period over which the restrictions are released and the stock certificates are given to the grantee. During the performance or vesting period, the grantee is not permitted to sell, transfer, pledge, encumber or assign shares of restricted stock granted under the Plan; however, the grantee has the ability to vote the shares and receive nonforfeitable dividends paid on shares. Unless otherwise determined by the CNG Committee at the time of grant, the forfeiture and transfer restrictions on the shares lapse over a four-year period beginning on the date of grant.

Option Grants

A summary of stock option activity is as follows:



Options	Number of Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value as of December 31, 2018
Outstanding at December 31, 2015	572,629		$	24.42
Granted	35,800		85.99
Exercised	(97,855	)	14.75
Outstanding at December 31, 2016	510,574		$	30.60
Exercised	(38,418	)	32.94
Outstanding at December 31, 2017	472,156		$	30.41
Exercised	(54,575	)	21.45
Outstanding at December 31, 2018	417,581		$	31.58	2.78	$24,597

Vested and Expected to Vest	416,567		$	31.46	2.77	$24,587
Ending Exercisable	377,292		$	26.72	2.35	$24,057

The aggregate intrinsic value in the table above represents the total value (the difference between the Company’s closing stock price on the last trading day of 2018 and the exercise price, multiplied by the number of in-the-money options) that would have been received by the option holders had all option holders exercised their options on December 31, 2018. The amount of aggregate intrinsic value will change based on the fair market value of the Company’s stock.

The weighted average fair value of stock options granted in 2016, was $20.30. There were no options granted in 2018 or 2017. The fair value of each option grant is estimated on the date of grant using the Black-Scholes option-pricing model with the following weighted average assumptions:



			For the Year Ended December 31,
			2016
Expected volatility			37.0%
Dividend yield			3.6%
Risk-free interest rate			1.3%
Average expected term (years)			5

The Black-Scholes model incorporates assumptions to value stock-based awards. The risk-free rate is based on the U.S. Treasury yield curve in effect at the time of the grant for the estimated life of the option. The Company uses actual historical data to calculate the expected price volatility, dividend yield and average expected term. The forfeiture rate, which is estimated at a weighted-average of 7.4% of unvested options outstanding as of December 31, 2018, is adjusted periodically based on the extent to which actual forfeitures differ, or are expected to differ, from the previous estimates.

A summary of stock options outstanding and exercisable as of December 31, 2018, is as follows:



	Options Outstanding				Options Exercisable
Exercise Price	Shares	Weighted Average Remaining Contractual Life	Weighted Average Exercise Price		Shares	Weighted Average Exercise Price
$6.22 - $6.22	139,250	0.13	$	6.22	139,250	$	6.22
$11.59 - $11.59	20,080	1.13	11.59		20,080	11.59
$12.21 - $12.21	77,400	1.18	12.21		77,400	12.21
$19.6 - $28.79	29,469	2.65	23.56		29,469	23.56
$38.4 - $38.4	10,360	4.14	38.4		10,360	38.40
$47.5 - $47.5	17,687	5.13	47.5		17,687	47.50
$65.36 - $65.36	20,395	6.15	65.36		15,297	65.36
$65.45 - $65.45	17,140	6.13	65.45		12,345	65.45
$73.52 - $73.52	50,000	6.58	73.52		37,500	73.52
$85.99 - $85.99	35,800	7.15	85.99		17,904	85.99
	417,581	2.78	$	31.58	377,292	$	26.72

The Company recorded compensation expense relating to outstanding options of $570, $649 and $729 in general and administrative expense for the years ended December 31, 2018, 2017 and 2016, respectively. Total cash received for the years ended December 31, 2018, 2017 and 2016, related to option exercises was $1,169, $1,266 and $1,444, respectively. At December 31, 2018, there was $344 of total unrecognized compensation expense related to non-vested stock options under the Plan. That cost is expected to be recognized over a weighted-average period of 0.72 years. The valuation model applied in this calculation utilizes subjective assumptions that could potentially change over time, including the expected forfeiture rate. Therefore, the amount of unrecognized compensation expense at December 31, 2018 noted above does not necessarily represent the expense that will ultimately be realized by the Company in the statement of operations.

Common Stock Granted to Employees and Directors

The Company recorded $10,606, $8,072 and $7,316 of expense in general and administrative expense in its statement of operations related to restricted stock awards granted to employees and directors for the years ended December 31, 2018, 2017 and 2016, respectively. The forfeiture rate, which is estimated at a weighted-average of 10.2% of unvested awards outstanding as of December 31, 2018, is adjusted periodically based on the extent to which actual forfeitures differ, or are expected to differ, from the previous estimates. At December 31, 2018 there was $10,870 of total unrecognized compensation expense related to non-vested restricted stock awards under the Plan. That cost is expected to be recognized over a weighted-average period of 2.00 years. The fair value of common stock awards is determined based on the closing trading price of the Company’s common stock on the grant date.

A summary of the Company’s employee and director share grant activity is as follows:



Restricted Stock Grants	Shares		Weighted-Average Grant-Date Fair Value
Unreleased at December 31, 2015	318,409		$	55.75
Granted	119,931		87.61
Released	(128,808	)	50.05
Cancelled	(9,947	)	67.36
Unreleased at December 31, 2016	299,585		$	70.57
Granted	95,392		74.49
Released	(120,323	)	63.95
Cancelled	(8,179	)	77.25
Unreleased at December 31, 2017	266,475		$	74.76
Granted	85,066		86.14
Released	(116,656	)	72.38
Cancelled	(11,771	)	80.96
Unreleased at December 31, 2018	223,114		$	80.02

Performance-based Stock Units

In 2017, the CNG Committee changed its compensation for executives to issue performance-based stock units (the "PSUs") as a replacement for stock option awards. The PSUs granted to executives represent the right to earn shares of the Company's common stock. These awards have two financial performance components: (1) the Company's core FFO performance ("FFO Target"), and (2) the Company's total stockholder return relative to the performance of a defined group of peers ("TSR Target"). Each of these performance components are weighted 50% and are measured over the performance period, which is defined as the three-year period ending December 31 from the year of grant. At the end of the performance period, the financial performance components are reviewed to determine the number of shares actually granted to executives, which can be as low as zero shares and up to a maximum of two shares issued for each PSU. A summary of the PSU activity is as follows:



Performance-Based Stock Units	Units	Weighted-Average Grant-Date Fair Value
Unvested at December 31, 2016	—	$	—
Granted	30,071	83.84
Unvested at December 31, 2017	30,071	$	83.84
Granted	28,735	96.19
Unvested at December 31, 2018	58,806	$	89.87

The Company estimated the fair value of the PSUs as of the grant date, using the closing trading price of the Company's common stock on the grant date to value the FFO Target portion. A Monte Carlo simulation model was used to calculate the fair value of the TSR Target portion of the PSUs, using the following assumptions:



	For the Year Ended December 31,
	2018	2017
Intrinsic value	$5,321	$2,630
Compensation cost	$1,873	$840
Risk-free rate	2.37%	1.62%
Volatility	22.6%	21.4%
Expected term (in years)	2.9	2.8
Dividend yield	—%	—%
Unrecognized compensation cost	$2,739	$1,681
Term over which unrecognized compensation cost recognized	2	2

Under the terms of the PSUs, dividends for the entire measurement period are paid in cash when the shares are issued, so a dividend yield of zero was used. The valuation model applied in this calculation utilizes subjective assumptions that could potentially change over time, including the probabilities associated with achieving the FFO Targets (categorized within Level 3 of the fair value hierarchy). Therefore, the amount of unrecognized compensation expense at December 31, 2018 noted above does not necessarily represent the expense that will ultimately be realized by the Company in the statement of operations.

Employee Benefit Plan	12 Months Ended
Employee Benefit Plan	Dec. 31, 2018
Retirement Benefits [Abstract]
Employee Benefit Plan	EMPLOYEE BENEFIT PLAN The Company has a retirement savings plan under Section 401(k) of the Internal Revenue Code under which eligible employees can contribute up to 60% of their annual salary, subject to a statutory prescribed annual limit. For the years ended December 31, 2018, 2017 and 2016, the Company made matching contributions to the plan of $2,833, $2,212 and $1,944, respectively, based on 100% of the first 3% and up to 50% of the next 2% of an employee’s compensation.

Income Taxes

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Income Taxes

INCOME TAXES

As a REIT, the Company is generally not subject to federal income tax with respect to that portion of its income which is distributed annually to its stockholders. However, the Company has elected to treat one of its corporate subsidiaries, Extra Space Management, Inc., as a TRS. In general, the Company’s TRS may perform additional services for tenants and generally may engage in any real estate or non-real estate related business. A TRS is subject to federal corporate income tax. The Company accounts for income taxes in accordance with the provisions of ASC 740, “Income Taxes.” Deferred tax assets and liabilities are determined based on differences between financial reporting and tax bases of assets and liabilities. The Company has elected to use the Tax-Law-Ordering approach to determine when excess tax benefits will be realized.

The income tax provision for the years ended December 31, 2018, 2017 and 2016, is comprised of the following components:



	For the Year Ended December 31, 2018
	Federal			State			Total
Current expense	$	9,136		$	2,426		$	11,562
Tax credits/true-up	(5,841		)	(175		)	(6,016		)
Change in deferred expense/(benefit)	3,730			(32		)	3,698
Total tax expense	$	7,025		$	2,219		$	9,244



	For the Year Ended December 31, 2017
	Federal			State			Total
Current expense	$	5,677		$	1,662		$	7,339
Tax credits/true-up	(5,573		)	(383		)	(5,956		)
Change in deferred expense	1,700			542			2,242
Total tax expense	$	1,804		$	1,821		$	3,625



	For the Year Ended December 31, 2016
	Federal			State			Total
Current expense	$	14,627		$	2,368		$	16,995
Tax credits/true-up	(312		)	—			(312		)
Change in deferred benefit	(369		)	(467		)	(836		)
Total tax expense	$	13,946		$	1,901		$	15,847

A reconciliation of the statutory income tax provisions to the effective income tax provisions for the periods indicated is as follows:



	For the Year Ended December 31,
	2018					2017					2016
Expected tax at statutory rate	$	95,828		21.0	%	$	186,274		35.0	%	$	144,708		35.0	%
Non-taxable REIT income	(83,022		)	(18.2	)%	(170,811		)	(32.1	)%	(131,112		)	(31.7	)%
State and local tax expense - net of federal benefit	2,385			0.5	%	2,306			0.4	%	2,399			0.6	%
Change in valuation allowance	(1,052		)	(0.2	)%	159			—	%	(845		)	(0.2	)%
Tax credits/true-up	(6,016		)	(1.3	)%	(5,956		)	(1.1	)%	(312		)	(0.1	)%
Remeasurement of deferred balances	—			—	%	(8,460		)	(1.6	)%	—			—	%
Miscellaneous	1,121			0.2	%	113			—	%	1,009			0.2	%
Total provision	$	9,244		2.0	%	$	3,625		0.6	%	$	15,847		3.8	%

The major sources of temporary differences stated at their deferred tax effects are as follows:



	December 31, 2018			December 31, 2017
Deferred tax liabilities:
Fixed assets	$	(20,907	)	$	(15,271	)
Other	(96		)	(108		)
State deferred taxes	(3,076		)	(2,822		)
Total deferred tax liabilities	(24,079		)	(18,201		)

Deferred tax assets:
Captive insurance subsidiary	324			252
Accrued liabilities	1,772			873
Stock compensation	1,604			1,287
Solar credit	—			43
Other	53			57
SmartStop TRS	219			219
State deferred taxes	7,196			7,802
Total deferred tax assets	11,168			10,533

Valuation allowance	(3,872		)	(4,924		)

Net deferred income tax liabilities	$	(16,783	)	$	(12,592	)

The state income tax net operating losses expire between 2019 and 2036. The valuation allowance is associated with the state income tax net operating losses. The tax years 2014 through 2017 remain open related to the state returns, and 2015 through 2017 for the federal returns.

Federal tax reform legislation that was enacted on December 22, 2017 (commonly known as the Tax Cuts and Jobs Act) (the “2017 Tax Legislation”) made substantial changes to the Internal Revenue Code. Among those changes were a reduction in the U.S. federal corporate tax rate from the previous rate of 35% to 21%, the elimination or modification of various allowed deductions, and a deduction for REIT stockholders that are individuals, trusts and estates of up to 20% of ordinary REIT dividends. Many of the provisions of the 2017 Tax Legislation required guidance through the issuance of Treasury regulations in order to assess their effect. It is possible that there will be technical corrections legislation proposed with respect to the 2017 Tax Legislation, the effect of which cannot be predicted and may be adverse to the Company or its stockholders.

The SEC staff issued SAB 118, which provides guidance on accounting for the tax effects of the 2017 Tax Legislation. SAB 118 provides a measurement period that should not extend beyond one year from the 2017 Tax Legislation enactment date for companies to complete the accounting under ASC 740. In accordance with SAB 118, a company must reflect the income tax effects of those aspects of the 2017 Tax Legislation for which the accounting under ASC 740 is complete. To the extent that a company’s accounting for certain income tax effects of the 2017 Tax Legislation is incomplete but it is able to determine a reasonable estimate, it must record a provisional estimate in the financial statements. If a company cannot determine a provisional estimate to be included in the financial statements, it should continue to apply ASC 740 on the basis of the provisions of the tax laws that were in effect immediately before the enactment of the 2017 Tax Legislation. The Company recorded a provisional estimate of the impact of the 2017 Tax Legislation for the year ended December 31, 2017. The SAB 118 measurement period closed on December 22, 2018. The Company's accounting for the 2017 Tax Legislation under SAB 118 has been finalized with no additional adjustments.

For the year ended December 31, 2017, the Company remeasured certain deferred tax assets and liabilities based on the rates at which they are expected to reverse in the future, which is generally 21%. The tax benefit recorded related to the remeasurement of the deferred tax balance and valuation allowance was $8,606, which is included as a component of income tax expense for the year ended December 31, 2017. The Company made no additional adjustments to this initial remeasurement for the year ended December 31, 2018.

Segment Information

12 Months Ended

Dec. 31, 2018

Segment Reporting [Abstract]

Segment Information

SEGMENT INFORMATION

The Company’s segment disclosures present the measure used by the chief operating decision makers ("CODMs") for purposes of assessing each segment’s performance. The Company’s CODMs are comprised of several members of its executive management team who use net operating income ("NOI") to assess the performance of the business for the Company’s reportable operating segments. NOI for our self-storage operations represents total property revenue less direct property operating expenses. NOI for our tenant reinsurance segment represents tenant reinsurance revenues less tenant reinsurance expense.

The Company’s segments, prior to 2017, were comprised of three reportable segments: (1) rental operations; (2) tenant reinsurance; and (3) property management, acquisition and development. Based on how the CODMs reviews performance and makes decisions, the Company realigned its segments into two reportable segments: (1) self-storage operations and (2) tenant reinsurance. The self-storage operations activities include rental operations of wholly-owned stores. The Company's consolidated revenues equal total segment revenues plus property management fees and other income. Tenant reinsurance activities include the reinsurance of risks relating to the loss of goods stored by tenants in the stores operated by the Company. Excluded from segment revenues and net operating income is property management fees and other income.

For all periods presented, substantially all of our real estate assets, intangible assets, other assets, and accrued and other liabilities are associated with the self-storage operations segment. The prior periods have been restated to conform to the current presentation. Financial information for the Company’s business segments is set forth below:



	Year Ended December 31,
	2018			2017			2016
Revenues:
Self-Storage Operations	$	1,039,340		$	967,229		$	864,742
Tenant Reinsurance	115,507			98,401			87,291
Total segment revenues	1,154,847			1,065,630			$	952,033

Operating expenses:
Self-Storage Operations	$	291,695		$	271,974		$	250,005
Tenant Reinsurance	25,707			19,173			15,555
Total segment operating expenses	$	317,402		$	291,147		$	265,560

Net operating income:
Self-Storage Operations	747,645			695,255			$	614,737
Tenant Reinsurance	89,800			79,228			71,736
Total segment net operating income:	$	837,445		$	774,483		$	686,473

Total segment net operating income	$	837,445		$	774,483		$	686,473
Other components of net income (loss):
Property management fees and other income	41,757			39,379			39,842
General and administrative expense	(81,256		)	(78,961		)	(81,806		)
Depreciation and amortization expense	(209,050		)	(193,296		)	(182,560		)
Acquisition and other related costs⁽¹⁾	—			—			(12,111		)
Gain on real estate transactions, earnout from prior acquisitions and impairment of real estate	30,807			112,789			8,465
Interest expense	(178,436		)	(153,511		)	(133,479		)
Non-cash interest expense related to the amortization of discount on equity component of exchangeable senior notes	(4,687		)	(5,103		)	(4,980		)
Interest income	5,292			6,736			10,998
Equity in earnings of unconsolidated real estate ventures	14,452			15,331			12,895
Equity in earnings of unconsolidated real estate ventures - gain on sale of real estate assets and purchase of partners' interests	—			—			69,199
Income tax expense	(9,244		)	(3,625		)	(15,847		)
Net income	$	447,080		$	514,222		$	397,089

(1) Beginning January 1, 2017, acquisition related costs have been capitalized due to the adoption of ASU 2017-01, "Business Combinations (Topic 805): Clarifying the Definition of a Business."

Commitments and Contingencies

12 Months Ended

Dec. 31, 2018

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

COMMITMENTS AND CONTINGENCIES

The Company has operating leases on its corporate offices and owns 23 stores that are subject to leases. At December 31, 2018, future minimum rental payments under these non-cancelable operating leases were as follows (unaudited):



Less than 1 year	$	8,203
Year 2	8,307
Year 3	8,137
Year 4	7,837
Year 5	7,021
Thereafter	111,653
	$	151,158

The Company recorded expense of $8,229, $6,898 and $4,578 related to operating leases in the years ended December 31, 2018, 2017 and 2016, respectively.

The Company is involved in various legal proceedings and is subject to various claims and complaints arising in the ordinary course of business. Because litigation is inherently unpredictable, the outcome of these matters cannot presently be determined with any degree of certainty. In accordance with applicable accounting guidance, management establishes an accrued liability for litigation when those matters present loss contingencies that are both probable and reasonably estimable. In such cases, there may be an exposure to loss in excess of any amounts accrued. The estimated loss, if any, is based upon currently available information and is subject to significant judgment, a variety of assumptions, and known and unknown uncertainties. The Company could in the future incur judgments or enter into settlements of claims that could have a material adverse effect on its results of operations in any particular period, notwithstanding the fact that the Company is currently vigorously defending any legal proceedings against it. As of December 31, 2018, the Company was involved in various legal proceedings and was subject to various claims and complaints arising in the ordinary course of business. In the opinion of management, such litigation, claims and complaints are not expected to have a material adverse effect on the Company’s financial condition or results of operations.

As of December 31, 2018, the Company was under agreement to acquire 18 stores at a total purchase price of $271,526. Of these stores, 16 are scheduled to close in 2019 at a purchase price of $247,498, and two are scheduled to close in 2020 at a purchase price of $24,028. Additionally, the Company is under agreement to acquire 13 stores with joint venture partners, for a total investment of $73,860. Eleven of these stores are scheduled to close in 2019, while the remaining two are scheduled to close in 2020.

Although there can be no assurance, the Company is not aware of any material environmental liability, for which it believes it will be ultimately responsible, that could have a material adverse effect on its financial condition or results of operations. However, changes in applicable environmental laws and regulations, the uses and conditions of properties in the vicinity of the Company’s properties, the activities of its tenants and other environmental conditions of which the Company is unaware with respect to its properties could result in future material environmental liabilities.

Supplementary Quarterly Financial Data (Unaudited)

12 Months Ended

Dec. 31, 2018

Quarterly Financial Information Disclosure [Abstract]

Supplementary Quarterly Financial Data (Unaudited)

SUPPLEMENTARY QUARTERLY FINANCIAL DATA (UNAUDITED)



	For the Three Months Ended
	March 31, 2018		June 30, 2018		September 30, 2018		December 31, 2018
Revenues	$	285,485	$	296,813	$	306,953	$	307,353
Cost of operations	151,573		152,097		153,362		150,676
Revenues less cost of operations	$	133,912	$	144,716	$	153,591	$	156,677
Net income	$	95,430	$	102,713	$	139,687	$	109,250
Net income attributable to common stockholders	$	88,256	$	95,153	$	130,418	$	101,462
Earnings per common share—basic	$	0.70	$	0.75	$	1.03	$	0.80
Earnings per common share—diluted	$	0.70	$	0.75	$	1.02	$	0.80
	For the Three Months Ended
	March 31, 2017		June 30, 2017		September 30, 2017		December 31, 2017
Revenues	$	263,008	$	276,003	$	284,156	$	281,842
Cost of operations	138,805		139,596		144,275		140,728
Revenues less cost of operations	$	124,203	$	136,407	$	139,881	$	141,114
Net income	$	89,734	$	94,098	$	101,075	$	229,315
Net income attributable to common stockholders	$	82,282	$	87,006	$	93,742	$	215,983
Earnings per common share—basic	$	0.65	$	0.69	$	0.74	$	1.71
Earnings per common share—diluted	$	0.64	$	0.69	$	0.74	$	1.69

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	SUBSEQUENT EVENTS Subsequent to year end, the Company acquired its joint venture partner's interests in Extra Space West One LLC and Extra Space West Two LLC. The 12 stores owned by these joint ventures are now wholly-owned by the Company. The Company paid cash of $172,515 and assumed an existing loan of $17,157.

Schedule III - Real Estate and Accumulated Depreciation

12 Months Ended

Dec. 31, 2018

SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation Disclosure [Abstract]

Schedule III - Real Estate and Accumulated Depreciation

Extra Space Storage Inc.

Schedule III

Real Estate and Accumulated Depreciation

(Dollars in thousands)

As of December 31, 2018



						Building and Improvements Initial Cost		Adjustments and Costs to Land and Building Subsequent to Acquisition		Gross carrying amount at December 31, 2018
Self - Storage Facilities by State:	Store Count			Land Initial Cost								Building and Improvements				Accumulated Depreciation
		Debt								Land				Total
AL	8	$	30,215	$	7,690	$	42,770	$	3,156	$	7,691	$	45,925	$	53,616	$	6,928
AZ	23	39,974		27,535		117,304		8,680		27,533		125,986		153,519		20,509
CA	146	699,982		446,176		1,069,102		91,467		446,863		1,159,882		1,606,745		227,969
CO	15	39,092		15,700		62,816		14,186		15,887		76,815		92,702		16,942
CT	7	23,869		9,875		50,966		3,861		9,874		54,828		64,702		8,279
FL	86	331,556		161,109		579,419		45,736		161,573		624,691		786,264		115,603
GA	59	104,806		77,306		372,157		22,117		77,290		394,290		471,580		48,711
HI	9	39,644		17,663		133,870		5,094		17,663		138,964		156,627		21,756
IL	31	58,189		44,427		225,423		21,944		43,449		248,345		291,794		35,630
IN	15	11,149		12,447		58,247		5,118		12,447		63,365		75,812		9,767
KS	1	—		366		1,897		529		366		2,426		2,792		997
KY	11	34,817		8,640		68,679		4,558		8,640		73,237		81,877		9,813
LA	2	—		6,114		8,541		1,297		6,115		9,837		15,952		3,919
MA	45	126,966		72,445		254,383		36,722		72,626		290,924		363,550		71,855
MD	32	140,841		99,147		284,253		14,408		97,180		300,628		397,808		61,719
MI	7	8,639		9,583		51,359		2,025		9,583		53,384		62,967		4,206
MN	4	—		6,681		42,252		277		6,681		42,529		49,210		1,348
MO	5	5,981		4,129		15,444		3,510		4,086		18,997		23,083		6,752
MS	3	—		2,420		20,849		1,403		2,420		22,252		24,672		1,983
NC	18	33,835		31,969		104,104		3,769		31,967		107,875		139,842		8,128
NH	2	6,024		754		4,054		1,108		817		5,099		5,916		2,225
NJ	59	201,091		134,032		560,512		34,227		134,479		594,292		728,771		113,188
NM	11	22,055		32,252		71,142		4,177		32,252		75,319		107,571		7,175
NV	14	35,797		15,252		74,376		4,081		15,252		78,457		93,709		8,114
NY	23	97,930		122,835		240,816		29,767		123,570		269,848		393,418		52,400
OH	17	43,789		17,788		50,493		5,983		17,787		56,477		74,264		11,500
OR	6	30,885		7,906		39,576		1,414		7,906		40,990		48,896		6,389
PA	17	34,544		23,376		132,317		9,331		22,668		142,356		165,024		19,949
RI	2	10,327		3,191		6,926		1,176		3,191		8,102		11,293		2,676
SC	23	44,560		37,075		135,760		8,834		37,076		144,593		181,669		18,349
TN	17	49,475		25,938		91,497		7,321		25,938		98,818		124,756		15,043
TX	99	279,717		169,160		648,128		52,440		169,012		700,716		869,728		91,986
UT	10	16,625		9,008		39,295		10,044		9,008		49,339		58,347		8,925
VA	46	228,363		139,318		414,335		16,668		139,319		431,002		570,321		56,712
WA	8	33,203		12,528		47,645		2,349		12,530		49,992		62,522		9,965
DC	1	9,038		14,394		18,172		356		14,394		18,528		32,922		1,311
Other corporate assets		—		—		2,202		116,855		—		119,057		119,057		32,473
Intangible tenant relationships and lease rights		—		—		132,000		—		—		132,000		132,000		121,238
Construction in Progress/Undeveloped Land		—		10,937		—		48,034		7,359		51,612		58,971		6
Totals	882	$	2,872,978	$	1,837,166	$	6,273,080	$	644,023	$	1,832,492	$	6,921,777	$	8,754,269	$	1,262,438

Activity in real estate facilities during the years ended December 31, 2018, 2017 and 2016 is as follows:



	2018			2017			2016
Operating facilities
Balance at beginning of year	$	8,158,741		$	7,649,448		$	6,392,487
Acquisitions	459,223			628,391			1,159,304
Improvements	64,336			71,090			92,480
Transfers from construction in progress	49,449			19,079			26,400
Dispositions and other	(22,434		)	(209,267		)	(21,223		)
Balance at end of year	$	8,709,315		$	8,158,741		$	7,649,448
Accumulated depreciation:
Balance at beginning of year	$	1,060,060		$	900,861		$	728,087
Depreciation expense	203,030			185,903			174,906
Dispositions and other	(652		)	(26,704		)	(2,132		)
Balance at end of year	$	1,262,438		$	1,060,060		$	900,861
Real estate under development/redevelopment:
Balance at beginning of year	$	33,750		$	21,860		$	24,909
Current development	60,677			33,484			23,404
Transfers to operating facilities	(49,449		)	(19,079		)	(26,400		)
Dispositions and other	(24		)	(2,515		)	(53		)
Balance at end of year	$	44,954		$	33,750		$	21,860
Net real estate assets	$	7,491,831		$	7,132,431		$	6,770,447

As of December 31, 2018, the aggregate cost of real estate for U.S. federal income tax purposes was $7,306,350.

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The consolidated financial statements are presented on the accrual basis of accounting in accordance with U.S. generally accepted accounting principles (“GAAP”) and include the accounts of the Company and its wholly- or majority-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.
Variable Interest Entities	Variable Interest Entities The Company accounts for arrangements that are not controlled through voting or similar rights as variable interest entities (“VIEs”). An enterprise is required to consolidate a VIE if it is the primary beneficiary of the VIE. A VIE is created when (i) the equity investment at risk is not sufficient to permit the entity to finance its activities without additional subordinated financial support from other parties, or (ii) the entity’s equity holders as a group either: (a) lack the power, through voting or similar rights, to direct the activities of the entity that most significantly impact the entity’s economic performance, (b) are not obligated to absorb expected losses of the entity if they occur, or (c) do not have the right to receive expected residual returns of the entity if they occur. If an entity is deemed to be a VIE, the enterprise that is deemed to have a variable interest, or combination of variable interests, that provides the enterprise with a controlling financial interest in the VIE, is considered the primary beneficiary and must consolidate the VIE. The Company has concluded that under certain circumstances when the Company enters into arrangements for the formation of joint ventures, a VIE may be created under condition (i), (ii) (b) or (c) of the previous paragraph. For each VIE created, the Company has performed a qualitative analysis, including considering which party, if any, has the power to direct the activities most significant to the economic performance of each VIE and whether that party has the obligation to absorb losses of the VIE or the right to receive benefits from the VIE that could be significant to the VIE. If the Company is determined to be the primary beneficiary of the VIE, the assets, liabilities and operations of the VIE are consolidated with the Company’s financial statements. Additionally, the Operating Partnership has notes payable to one trust that is a VIE under condition (ii)(a) above. Since the Operating Partnership is not the primary beneficiary of the trust, this VIE is not consolidated. The Company’s investments in real estate joint ventures, where the Company has significant influence, but not control, and joint ventures which are VIEs in which the Company is not the primary beneficiary, are recorded under the equity method of accounting on the accompanying consolidated financial statements.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Fair Value Disclosures	Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis Long-lived assets held for use are evaluated for impairment when events or circumstances indicate there may be impairment. The Company reviews each store at least annually to determine if any such events or circumstances have occurred or exist. The Company focuses on stores where occupancy and/or rental income have decreased by a significant amount. For these stores, the Company determines whether the decrease is temporary or permanent, and whether the store will likely recover the lost occupancy and/or revenue in the short term. In addition, the Company reviews stores in the lease-up stage and compares actual operating results to original projections. When the Company determines that an event that may indicate impairment has occurred, the Company compares the carrying value of the related long-lived assets to the undiscounted future net operating cash flows attributable to the assets. An impairment loss is recorded if the net carrying value of the assets exceeds the undiscounted future net operating cash flows attributable to the assets. The impairment loss recognized equals the excess of net carrying value over the related fair value of the assets. When real estate assets are identified by management as held for sale, the Company discontinues depreciating the assets and estimates the fair value of the assets, net of selling costs. The Company compares the carrying value of the related long-lived assets to the undiscounted future net operating cash flows attributable to the assets (categorized within Level 3 of the fair value hierarchy). If the estimated fair value, net of selling costs, of the assets that have been identified as held for sale is less than the net carrying value of the assets, the Company would recognize a loss on the assets held for sale. The operations of assets held for sale or sold during the period are presented as part of normal operations for all periods presented. The Company assesses annually whether there are any indicators that the value of the Company’s investments in unconsolidated real estate ventures may be impaired and when events or circumstances indicate that there may be impairment. An investment is impaired if management’s estimate of the fair value of the investment is less than its carrying value. To the extent impairment has occurred, and is considered to be other than temporary, the loss is measured as the excess of the carrying amount of the investment over the fair value of the investment. As of December 31, 2018 and 2017, the Company did not have any assets or liabilities measured at fair value on a nonrecurring basis. Fair Value of Financial Instruments The carrying values of cash and cash equivalents, restricted cash, receivables, other financial instruments included in other assets, accounts payable and accrued expenses, variable-rate notes payable, revolving lines of credit and other liabilities reflected in the consolidated balance sheets at December 31, 2018 and 2017, approximate fair value. The fair values of the Company’s notes receivable from Preferred Operating Partnership unit holders and other fixed rate notes receivable were based on the discounted estimated future cash flow of the notes (categorized within Level 3 of the fair value hierarchy); the discount rate used approximated the current market rate for loans with similar maturities and credit quality. The fair values of the Company’s fixed rate notes payable and notes payable to trusts were estimated using the discounted estimated future cash payments to be made on such debt (categorized within Level 3 of the fair value hierarchy); the discount rates used approximated current market rates for loans, or groups of loans, with similar maturities and credit quality. The fair value of the Company’s exchangeable senior notes was estimated using an average market price for similar securities obtained from a third party. Fair Value Disclosures Derivative financial instruments Currently, the Company uses interest rate swaps to manage its interest rate risk. The valuation of these instruments is determined using widely accepted valuation techniques including discounted cash flow analysis on the expected cash flows of each derivative. This analysis reflects the contractual terms of the derivatives, including the period to maturity, and uses observable market-based inputs, including interest rate curves. The fair values of interest rate swaps are determined using the market standard methodology of netting the discounted future fixed cash payments and the discounted expected variable cash receipts. The variable cash receipts are based on an expectation of future interest rates (forward curves) derived from observable market interest rate forward curves. The Company incorporates credit valuation adjustments to appropriately reflect both its own nonperformance risk and the respective counterparty’s nonperformance risk in the fair value measurements. In adjusting the fair value of its derivative contracts for the effect of nonperformance risk, the Company has considered the impact of netting and any applicable credit enhancements, such as collateral postings, thresholds, mutual puts, and guarantees. In conjunction with the Financial Accounting Standard Board’s fair value measurement guidance, the Company made an accounting policy election to measure the credit risk of its derivative financial instruments that are subject to master netting agreements on a net basis by counterparty portfolio. Although the Company has determined that the majority of the inputs used to value its derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with its derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default by itself and its counterparties. However, as of December 31, 2018, the Company has assessed the significance of the impact of the credit valuation adjustments on the overall valuation of its derivative positions and has determined that the credit valuation adjustments are not significant to the overall valuation of its derivatives. As a result, the Company has determined that its derivative valuations in their entirety are classified in Level 2 of the fair value hierarchy.
Real Estate Assets	Real Estate Assets Real estate assets are stated at cost, less accumulated depreciation. Direct and allowable internal costs associated with the development, construction, renovation, and improvement of real estate assets are capitalized. Interest, property taxes, and other costs associated with development incurred during the construction period are capitalized. The construction period begins when expenditures for the real estate assets have been made and activities that are necessary to prepare the asset for its intended use are in progress. The construction period ends when the asset is substantially complete and ready for its intended use. Expenditures for maintenance and repairs are charged to expense as incurred. Major replacements and betterments that improve or extend the life of the asset are capitalized and depreciated over their estimated useful lives. Depreciation is computed using the straight-line method over the estimated useful lives of the buildings and improvements, which are generally between five and 39 years. Stores purchased at the time of certificate of occupancy issuance and stores purchased subsequent to the Company's adoption of ASU 2017-01 on January 1, 2017 are considered asset acquisitions. As such, the purchase price is allocated to the real estate assets acquired based on their relative fair values, which are estimated using significant unobservable inputs. The value of the tangible assets, consisting of land and buildings, is determined as if vacant. Intangible assets, which represent the value of existing tenant relationships, are recorded at their relative fair values based on the avoided cost to replace the current leases. The Company measures the value of tenant relationships based on the rent lost due to the amount of time required to replace existing customers, which is based on the Company’s historical experience with turnover in its stores. Any debt assumed as part of the acquisition is recorded at fair value based on current interest rates compared to contractual rates. Acquisition-related transactions costs are capitalized as part of the purchase price. Intangible lease rights represent: (1) purchase price amounts allocated to leases on three stores that cannot be classified as ground or building leases; these rights are amortized to expense over the life of the leases and (2) intangibles related to ground leases on eight stores where the leases were assumed by the Company at rates that were lower than the current market rates for similar leases. The values associated with these assumed leases were recorded as intangibles, which will be amortized over the lease terms.
Investments in Unconsolidated Real Estate Ventures	Investments in Unconsolidated Real Estate Ventures The Company’s investments in real estate joint ventures, where the Company has significant influence, but not control and joint ventures which are VIEs in which the Company is not the primary beneficiary, are recorded under the equity method of accounting in the accompanying consolidated financial statements. Under the equity method, the Company’s investment in real estate ventures is stated at cost and adjusted for the Company’s share of net earnings or losses and reduced by distributions. Equity in earnings of real estate ventures is generally recognized based on the Company’s ownership interest in the earnings of each of the unconsolidated real estate ventures. For the purposes of presentation in the statement of cash flows, the Company follows the “look through” approach for classification of distributions from joint ventures. Under this approach, distributions are reported under operating cash flow unless the facts and circumstances of a specific distribution clearly indicate that it is a return of capital (e.g., a liquidating dividend or distribution of the proceeds from the joint venture’s sale of assets), in which case it is reported as an investing activity.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company’s cash is deposited with financial institutions located throughout the United States and at times may exceed federally insured limits. The Company considers all highly liquid debt instruments with a maturity date of three months or less to be cash equivalents.
Restricted Cash	Restricted Cash Restricted cash is comprised of letters of credit and escrowed funds deposited with financial institutions located throughout the United States relating to earnest money deposits on potential acquisitions, real estate taxes, insurance and capital expenditures.
Other Assets	Other Assets Other assets consist of equipment and fixtures, rents receivable from our tenants, investments in trusts, notes and other receivables, other intangible assets, deferred tax assets, prepaid expenses and the fair value of interest rate swaps. Depreciation of equipment and fixtures is computed on a straight-line basis over three to five years.
Derivative Instruments and Hedging Activities	Derivative Instruments and Hedging Activities The Company records all derivatives on the balance sheet at fair value. The accounting for changes in the fair value of derivatives depends on the intended use of the derivative, whether the Company has elected to designate a derivative in a hedging relationship and apply hedge accounting and whether the hedging relationship has satisfied the criteria necessary to apply hedge accounting. Derivatives designated and qualifying as a hedge of the exposure to changes in the fair value of an asset, liability or firm commitment attributable to a particular risk, such as interest rate risk, are considered fair value hedges. Derivatives designated and qualifying as a hedge of the exposure to variability in expected future cash flows, or other types of forecasted transactions, are considered cash flow hedges. Hedge accounting generally provides for the matching of the timing of gain or loss recognition on the hedging instrument with the recognition of the changes in the fair value of the hedged asset or liability that are attributable to the hedged risk in a fair value hedge or the earnings effect of the hedged forecasted transactions in a cash flow hedge. The Company may enter into derivative contracts that are intended to economically hedge certain of its risk, even though hedge accounting does not apply or the Company elects not to apply hedge accounting. The Company made an accounting policy election to measure the credit risk of its derivative financial instruments that are subject to master netting agreements on a net basis by counterparty portfolio.
Risk Management and Use of Financial Instruments	Risk Management and Use of Financial Instruments In the normal course of its ongoing business operations, the Company encounters economic risk. There are three main components of economic risk: interest rate risk, credit risk and market risk. The Company is subject to interest rate risk on its interest-bearing liabilities. Credit risk is the risk of inability or unwillingness of tenants to make contractually required payments. Market risk is the risk of declines in the value of stores due to changes in rental rates, interest rates or other market factors affecting the value of stores held by the Company. The Company has entered into interest rate swap agreements to manage a portion of its interest rate risk.
Exchange of Common Operating Partnership Units	Exchange of Common Operating Partnership Units Redemption of common Operating Partnership units for shares of common stock, when redeemed under the original provisions of the Operating Partnership agreement, are accounted for by reclassifying the underlying net book value of the units from noncontrolling interest to the Company’s equity.
Revenue and Expense Recognition	Revenue and Expense Recognition Rental revenues are recognized as earned based upon amounts that are currently due from tenants. Leases are generally on month-to-month terms. Prepaid rents are recognized on a straight-line basis over the term of the leases. Promotional discounts are recognized as a reduction to rental income over the promotional period. Late charges, administrative fees and merchandise sales are recognized as income when earned. Equity in earnings of unconsolidated real estate entities is recognized based on the Company's ownership interest in the earnings of each of the unconsolidated real estate entities. Interest income is recognized as earned. The Company's management fees are earned subject to the terms of the related management services agreements ("MSAs"). These MSAs provide that the Company will perform management services, which include leasing and operating the property and providing accounting, marketing, banking, maintenance and other services. These services are provided in exchange for monthly management fees, which are based on a percentage of revenues collected from stores owned by third parties and unconsolidated joint ventures. MSAs generally have original terms from three to five years, after which management services are provided on a month-to-month basis unless terminated. Management fees are due on the last day of each calendar month that management services are provided. The Company accounts for the management services provided to a customer as a single performance obligation which are rendered over time each month. The total amount of consideration from the contract is variable as it is based on monthly revenues, which are influenced by multiple factors, some of which are outside the Company's control. Therefore, the Company recognizes the revenue at the end of each month once the uncertainty is resolved. Due to the standardized terms of the MSAs, the Company accounts for all MSAs in a similar, consistent manner. Therefore, no disaggregated information relating to MSAs is presented. Property expenses, including utilities, property taxes, repairs and maintenance and other costs to manage the facilities are recognized as incurred. The Company accrues for property tax expense based upon invoice amounts and estimates. If these estimates are incorrect, the timing of expense recognition could be affected. Tenant reinsurance premiums are recognized as revenue over the period of insurance coverage. The Company records an unpaid claims liability at the end of each period based on existing unpaid claims and historical claims payment history. The unpaid claims liability represents an estimate of the ultimate cost to settle all unpaid claims as of each period end, including both reported but unpaid claims and claims that may have been incurred but have not been reported. The Company uses a third party claims administrator to adjust all tenant reinsurance claims received. The administrator evaluates each claim to determine the ultimate claim loss and includes an estimate for claims that may have been incurred but not reported. Annually, a third party actuary evaluates the adequacy of the unpaid claims liability. Prior year claim reserves are adjusted as experience develops or new information becomes known. The impact of such adjustments is included in the current period operations. The unpaid claims liability is not discounted to its present value. Each tenant chooses the amount of insurance coverage they want through the tenant reinsurance program. Tenants can purchase policies in amounts of 2,000 dollars to 10,000 dollars of insurance coverage in exchange for a monthly fee. As of December 31, 2018, the average insurance coverage for tenants was approximately 2,900 dollars. The Company’s exposure per claim is limited by the maximum amount of coverage chosen by each tenant. The Company purchases reinsurance for losses exceeding a set amount for any one event. The Company does not currently have any amounts recoverable under the reinsurance arrangements. For the years ended December 31, 2018, 2017 and 2016, the number of claims made were 7,870, 5,671 and 4,055, respectively. The following table presents information on the portion of the Company’s unpaid claims liability, which is included in other liabilities on the Company's consolidated balance sheets, that relates to tenant insurance for the periods indicated:
Advertising Costs	Advertising Costs The Company incurs advertising costs primarily attributable to digital and other advertising. These costs are expensed as incurred. The Company recognized $16,153, $14,410 and $12,867 in advertising expense for the years ended December 31, 2018, 2017 and 2016, respectively, which are included in property operating expenses on the Company’s consolidated statements of operations.
Income Taxes	Income Taxes The Company has elected to be treated as a REIT under Sections 856 through 860 of the Internal Revenue Code of 1986, as amended (the "Internal Revenue Code"). In order to maintain its qualification as a REIT, among other things, the Company is required to distribute at least 90% of its REIT taxable income to its stockholders and meet certain tests regarding the nature of its income and assets. As a REIT, the Company is not subject to federal income tax with respect to that portion of its income which meets certain criteria and is distributed annually to stockholders. The Company plans to continue to operate so that it meets the requirements for taxation as a REIT. Many of these requirements, however, are highly technical and complex. For any taxable year that the Company fails to qualify as a REIT and for which applicable statutory relief provisions did not apply, we would be taxed at the regular corporate rates on all of our taxable income for at least that year and the ensuing four years. The Company is subject to certain state and local taxes. Provision for such taxes has been included in income tax expense on the Company’s consolidated statements of operations. For the year ended December 31, 2018, 0% (unaudited) of all distributions to stockholders qualified as a return of capital. The Company has elected to treat its corporate subsidiary, Extra Space Management, Inc. (“ESMI”), as a taxable REIT subsidiary (“TRS”). In general, the Company’s TRS may perform additional services for tenants and may engage in any real estate or non-real estate related business. A TRS is subject to federal corporate income tax. ESM Reinsurance Limited, a wholly-owned subsidiary of ESMI, generates income from insurance premiums that are subject to federal corporate income tax and state insurance premiums tax. Deferred tax assets and liabilities are determined based on differences between financial reporting and tax bases of assets and liabilities. At December 31, 2018 and 2017, there were no material unrecognized tax benefits. Interest and penalties relating to uncertain tax positions will be recognized in income tax expense when incurred. As of December 31, 2018 and 2017, the Company had no interest or penalties related to uncertain tax provisions.
Stock-Based Compensation	Stock-Based Compensation The measurement and recognition of compensation expense for all share-based payment awards to employees and directors are based on estimated fair values. Awards granted are valued at fair value and any compensation expense is recognized over the service periods of each award.
Earnings Per Common Share	The Operating Partnership had $575,000 of its 3.125% Exchangeable Senior Notes due 2035 (the “2015 Notes”) issued and outstanding as of December 31, 2018. The 2015 Notes could potentially have a dilutive impact on the Company’s earnings per share calculations. The 2015 Notes are exchangeable by holders into shares of the Company’s common stock under certain circumstances per the terms of the indenture governing the 2015 Notes. The exchange price of the 2015 Notes was $92.80 per share as of December 31, 2018, and could change over time as described in the indenture. The Company has irrevocably agreed to pay only cash for the accreted principal amount of the 2015 Notes relative to its exchange obligations, but retained the right to satisfy the exchange obligation in excess of the accreted principal amount in cash and/or common stock. Though the Company has retained that right, Accounting Standards Codification (“ASC”) 260, “Earnings per Share,” requires an assumption that shares would be used to pay the exchange obligation in excess of the accreted principal amount, and requires that those shares be included in the Company’s calculation of weighted average common shares outstanding for the diluted earnings per share computation. As of December 31, 2018, the Company had repaid the principal and accrued interest of its Exchangeable Senior Notes due 2033 (the “2013 Notes”), and therefore, no shares underlying the 2013 Notes were included in the dilution calculation for 2018. For the years ended December 31, 2017 and 2016, 344,430 shares and 309,730 shares, respectively, related to the 2013 Notes were included in the computation for diluted earnings per share. For the years ended December 31, 2018, 2017 and 2016, no shares related to the 2015 Notes were included in the computation for diluted earnings per share as the exchange price exceeded the per share price of the Company’s common stock during this period. For the purposes of computing the diluted impact on earnings per share of the potential exchange of Series A Units for common shares upon redemption, where the Company has the option to redeem in cash or shares and where the Company has stated the positive intent and ability to settle at least $101,700 of the instrument in cash (or net settle a portion of the Series A Units against the related outstanding note receivable), only the amount of the instrument in excess of $101,700 is considered in the calculation of shares contingently issuable for the purposes of computing diluted earnings per share as allowed by ASC 260-10-45-46.
Recently Issued Accounting Standards	Recently Issued Accounting Standards In May 2014, the Financial Accounting Standards Board ("FASB") issued ASU 2014-9, “Revenue from Contracts with Customers,” ("Topic 606") which amends the guidance for revenue recognition to replace numerous, industry-specific requirements and converges areas under this topic with those of the International Financial Reporting Standards. Topic 606 outlines a five-step process for customer contract revenue recognition that focuses on transfer of control, as opposed to transfer of risk and rewards. The amendment also requires enhanced disclosures regarding the nature, amount, timing and uncertainty of revenues and cash flows from contracts with customers. Topic 606 became effective for annual and interim periods beginning after December 15, 2017. The Company determined that its property rental revenue and tenant reinsurance revenue are not subject to the guidance in Topic 606, as they qualify as lease contract and insurance contracts, which are excluded from its scope. The Company's management fee revenue is included in the scope of Topic 606, and revenue recognized under the standard does not differ materially from revenue recognized under previous guidance. The Company adopted the standard using the modified retrospective transition method as of January 1, 2018. The Company's adoption of Topic 606 did not result in a cumulative catch-up adjustment or any significant changes to financial statement line items. In February 2016, the FASB issued ASU 2016-02, "Leases (Topic 842)," which modifies the accounting for leases, intending to increase transparency and comparability of organizations by requiring balance sheet presentation of leased assets and increased financial statement disclosure of leasing arrangements. ASU 2016-02 will require entities to recognize a liability for their lease obligations and a corresponding asset representing the right to use the underlying asset over the lease term. Lease obligations are to be measured at the present value and accounted for using the effective interest method. The accounting for the leased asset will differ slightly depending on whether the agreement is deemed to be a financing or operating lease. For finance leases, the leased asset is depreciated on a straight-line basis and recorded separately from the interest expense in the statements of operations, resulting in higher expense in the earlier part of the lease term. For operating leases, the depreciation and interest expense components are combined, recognized evenly over the term of the lease, and presented as a reduction to operating income. ASU 2016-02 requires that assets and liabilities be presented or disclosed separately, and requires additional disclosure of certain qualitative and quantitative information related to these lease agreements. ASU 2016-02 is effective for annual periods beginning after December 15, 2018. The Company plans to adopt the standard using the modified retrospective approach as of January 1, 2019. The Company expects to elect the package of practical expedients upon adoption, which allows for the application of the standard solely to the transition period in 2019 but does not require application to prior fiscal comparative periods presented. The Company estimates that the cumulative catch-up adjustment recorded upon adoption will not have a significant impact on retained earnings. The primary impact is expected to be related to the Company's 23 operating ground leases and two corporate facility leases under which it serves as lessee. The Company estimates the lease assets and lease liabilities to be between $90,000 and $110,000 related to its operating leases upon the adoption of Topic 842. In October 2016, the FASB issued ASU 2016-18, "Statement of Cash Flows (Topic 230): Restricted Cash," which requires that a statement of cash flows explains the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Therefore, amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. This guidance is effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. The Company adopted this guidance as of January 1, 2018, and now presents restricted cash along with cash and cash equivalents in its consolidated statements of cash flows. Prior periods have been reclassified to conform to the current year's presentation. In January 2017, the FASB issued ASU 2017-01, "Business Combinations (Topic 805) - Clarifying the Definition of a Business," which provides guidance on whether transactions should be accounted for as acquisitions or disposals of assets or businesses. Specifically, when substantially all of the fair value of the gross assets acquired (or disposed of) is concentrated in a single identifiable asset or a group of similar identifiable assets, the set is not a business. Additionally, ASU 2017-01 also provides other guidance providing a more robust framework to use in determining whether a set of assets and activities is a business. This guidance is effective for annual periods beginning after December 15, 2017. Early application of ASU 2017-01 is permitted for transactions for which the acquisition or disposition date occurs before the issuance date or effective date of the amendments, only when the transaction has not been reported in financial statements that have been issued. The Company adopted the guidance in ASU 2017-01 prospectively to new acquisitions beginning on January 1, 2017. The adoption of this guidance resulted in a decrease in acquisition related costs, as the Company's acquisition of operating stores are considered asset acquisitions rather than business combinations under ASU 2017-01, and such costs are capitalized under the new guidance. In August 2017, the FASB issued ASU 2017-12, "Derivatives and Hedging (Topic 815): Targeted Improvements for Accounting for Hedging Activities," which amends and simplifies existing guidance for the financial reporting of hedging relationships to allow companies to better portray the economic effects of risk management activities in their financial statements. ASU 2017-12 is effective for annual periods beginning after December 15, 2018, with early adoption permitted. The Company adopted this standard on January 1, 2018. The adoption of this standard did not have a material impact on the Company's financial statements. In August 2018, the FASB issued ASU 2018-15, "Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40): Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That is a Service Contract." ASU 2018-15 amends the accounting for implementation costs incurred in a hosting arrangement that is a service contract, and aligns them with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. ASU 2018-15 also requires that entities amortize the capitalized implementation costs over the term of the hosting arrangement. ASU 2018-15 is effective for annual periods beginning after December 15, 2020, with early adoption permitted, including early adoption in any interim period. The Company adopted this guidance on a prospective basis as of October 1, 2018. The adoption of this standard did not have a material impact on the Company's financial statements.
Convertible Debt	GAAP requires entities with convertible debt instruments that may be settled entirely or partially in cash upon conversion to separately account for the liability and equity components of the instrument in a manner that reflects the issuer’s economic interest cost. The Company therefore accounts for the liability and equity component of the 2015 Notes separately. The equity components are included in paid-in capital in stockholders’ equity in the consolidated balance sheets, and the value of the equity components are treated as original issue discount for purposes of accounting for the debt components. The discount is being amortized as interest expense over the remaining period of the debt through its first redemption date, October 1, 2020 for the 2015 Notes. The effective interest rate on the liability components of the 2015 Notes is 4.0%, which approximates the market rate of interest of similar debt without exchange features (i.e. nonconvertible debt) at the time of issuance.

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis



				Fair Value Measurements at Reporting Date Using
Description	December 31, 2018			Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)			Significant Unobservable Inputs (Level 3)
Other assets - Cash Flow Hedge Swap Agreements	$	42,324		$	—	$	42,324		$	—
Other liabilities - Cash Flow Hedge Swap Agreements	$	(2,131	)	$	—	$	(2,131	)	$	—

Schedule of Fair Value of Financial Instruments

The fair values of the Company’s fixed-rate assets and liabilities were as follows for the periods indicated:



	December 31, 2018				December 31, 2017
	Fair Value		Carrying Value		Fair Value		Carrying Value
Notes receivable from Preferred and Common Operating Partnership unit holders	$	115,467	$	119,735	$	113,683	$	120,230
Fixed rate notes receivable	$	—	$	—	$	20,942	$	20,608
Fixed rate notes payable and notes payable to trusts	$	2,985,731	$	3,022,414	$	2,774,242	$	2,815,085
Exchangeable senior notes	$	620,149	$	575,000	$	719,056	$	624,259

Schedule of Unpaid Claims Liability

The following table presents information on the portion of the Company’s unpaid claims liability, which is included in other liabilities on the Company's consolidated balance sheets, that relates to tenant insurance for the periods indicated:



	For the Year Ended December 31,
Tenant Reinsurance Claims:	2018			2017			2016
Unpaid claims liability at beginning of year	$	5,167		$	3,896		$	3,908
Claims and claim adjustment expense for claims incurred in the current year	15,800			11,700			7,250
Claims and claim adjustment expense (benefit) for claims incurred in the prior years	107			(203		)	87
Payments for current year claims	(11,010		)	(8,895		)	(5,423		)
Payments for prior year claims	(2,738		)	(1,331		)	(1,926		)
Unpaid claims liability at the end of the year	$	7,326		$	5,167		$	3,896

Schedule of Antidilutive Shares Excluded from Computation of Earnings Per Share



	For the Year Ended December 31,
	2018	2017	2016
	Equivalent Shares (if converted)	Equivalent Shares (if converted)	Equivalent Shares (if converted)
Common OP Units	—	—	5,564,631
Series A Units (Variable Only)	—	—	875,480
Series B Units	464,033	533,174	499,966
Series C Units	312,075	377,135	353,646
Series D Units	1,019,524	—	552,796
	1,795,632	910,309	7,846,519

Schedule of Computation of Earnings Per Common Share

The computation of earnings per share is as follows for the periods presented:



	For the Year Ended December 31,
	2018			2017			2016
Net income attributable to common stockholders	$	415,289		$	479,013		$	366,127
Earnings and dividends allocated to participating securities	(723		)	(975		)	(792		)
Earnings for basic computations	414,566			478,038			365,335
Earnings and dividends allocated to participating securities	723			—			792
Income allocated to noncontrolling interest - Preferred Operating Partnership Units and Operating Partnership Units	22,831			30,088			—
Fixed component of income allocated to noncontrolling interest - Preferred Operating Partnership (Series A Units)	(2,288		)	(3,119		)	—
Net income for diluted computations	$	435,832		$	505,007		$	366,127

Weighted average common shares outstanding:
Average number of common shares outstanding - basic	126,087,487			125,967,831			125,087,554
OP Units	5,675,547			5,590,831			—
Series A Units	875,480			875,480			—
Series D Units	—			1,081,561			—
Unvested restricted stock awards included for treasury stock method	244,215			—			299,585
Shares related to exchangeable senior notes and dilutive stock options	276,304			640,068			560,937
Average number of common shares outstanding - diluted	133,159,033			134,155,771			125,948,076
Earnings per common share
Basic	$	3.29		$	3.79		$	2.92
Diluted	$	3.27		$	3.76		$	2.91

Real Estate Assets (Tables)

12 Months Ended

Dec. 31, 2018

Real Estate [Abstract]

Schedule of Components of Real Estate Assets

The components of real estate assets are summarized as follows:



	December 31, 2018			December 31, 2017
Land - operating	$	1,825,133		$	1,731,915
Land - development	7,359			13,246
Buildings, improvements and other intangibles	6,743,355			6,286,762
Intangible assets - tenant relationships	119,557			114,375
Intangible lease rights	12,443			12,443
	8,707,847			8,158,741
Less: accumulated depreciation and amortization	(1,262,438		)	(1,060,060		)
Net operating real estate assets	7,445,409			7,098,681
Real estate under development/redevelopment	46,422			33,750
Net real estate assets	$	7,491,831		$	7,132,431
Real estate assets held for sale included in net real estate assets	$	13,032		$	10,276

Property Acquisitions and Dispositions (Tables)

12 Months Ended

Dec. 31, 2018

Real Estate [Abstract]

Schedule of Operating Properties Acquired

The following table shows the Company’s acquisitions of stores for the years ended December 31, 2018 and 2017. The table excludes purchases of raw land or improvements made to existing assets.



			Consideration Paid																		Total
Quarter	Number of Stores		Total		Cash Paid		Loan Assumed		Non- controlling interests			Investments in Real Estate Ventures			Net Liabilities/ (Assets) Assumed			Value of OP Units Issued		Number of OP Units Issued	Real estate assets
Q4 2018	6		$	74,852	$	74,868	$	—	$	—		$	—		$	(16	)	$	—	—	$	74,852
Q3 2018	6		74,694		71,989		—		—			—			2,705			—		—	74,694
Q2 2018	17		237,284		148,650		87,500		—			(1,024		)	281			1,877		21,768	237,284
Q1 2018	5		70,787		70,171		—		—			489			127			—		—	70,787
	34	⁽¹⁾	$	457,617	$	365,678	$	87,500	$	—		$	(535	)	$	3,097		$	1,877	21,768	$	457,617

Q4 2017	37		$	535,299	$	502,845	$	14,592	$	(1,812	)	$	12,957		$	1,099		$	5,618	64,708	$	535,299
Q3 2017	4		31,966		29,919		—		—			—			47			2,000		25,520	31,966
Q2 2017	3		34,641		16,608		9,463		1,827			—			(67		)	6,810		272,400	34,641
Q1 2017	2		25,556		25,541		—		—			—			15			—		—	25,556
	46	⁽²⁾	$	627,462	$	574,913	$	24,055	$	15		$	12,957		$	1,094		$	14,428	362,628	$	627,462


(1)	Store acquisitions during the year ended December 31, 2018 include the acquisition of 15 stores previously held in joint ventures where the Company held a noncontrolling interest. The Company purchased its partners' remaining equity interests in the joint ventures, and the properties owned by the joint ventures became wholly owned by the Company.


(2)	Store acquisitions during the year ended December 31, 2017 include the acquisition of seven stores that had been owned by joint ventures in which the Company held an equity interest.

Investments in Unconsolidated Real Estate Ventures - (Tables)

12 Months Ended

Dec. 31, 2018

Equity Method Investments and Joint Ventures [Abstract]

Schedule of Investments in Unconsolidated Real Estate Ventures

Investments in unconsolidated real estate ventures and cash distributions in unconsolidated real estate ventures consist of the following:



	Number of Stores	Equity Ownership %	Excess Profit %	December 31,
	Number of Stores	Equity Ownership %	Excess Profit %	2018			2017
WICNN JV LLC	7	10%	25%	$	26,885		$	—
VRS Self Storage, LLC	16	45%	54%	18,281			19,467
PRISA Self Storage LLC	85	4%	4%	9,334			9,638
Alan Jathoo JV LLC	9	10%	10%	8,180			—
Extra Space West Two LLC ⁽¹⁾	5	5%	40%	3,818			3,939
ESS Bristol Investments LLC	7	10%	28%	2,331			1,258
WCOT Self Storage LLC	—	5%	20%	—			(357		)
Extra Space West One LLC ⁽¹⁾	7	5%	40%	(1,038		)	(900		)
Extra Space Northern Properties Six LLC	10	10%	35%	(1,700		)	(1,279		)
Storage Portfolio II JV LLC	36	10%	30%	(4,233		)	(3,140		)
Storage Portfolio I LLC	24	34%	49%	(38,129		)	11,495
Other minority owned stores (17 joint ventures)	23	10-50%	19-50%	56,400			29,970
Net Investments in and Cash distributions in unconsolidated real estate ventures	229			$	80,129		$	70,091


(1)	Subsequent to year end, the Company acquired its joint venture partner's interests in Extra Space West One LLC and Extra Space West Two LLC joint ventures. The 12 stores owned by these joint ventures became wholly-owned by the Company subsequent to this acquisition. The Company paid cash of $172,515 and assumed an existing loan of $17,157.

Equity Method Investments

Information about these real estate ventures is summarized as follows:



	Number of Stores	Equity ownership %	Investment in new stores
For the Year Ended December 31, 2018⁽¹⁾	28	10.0% -50.0%	$	63,723
For the Year Ended December 31, 2017	39	10.0% - 25.0%	$	13,341
For the Year Ended December 31, 2016	8	20.0% - 50.0%	$	26,387


(1)	Included in the new unconsolidated joint ventures for the year ended December 31, 2018 were two new joint ventures (WICNN JV LLC and GFV JV, LLC), in which the Company has $22,734 and $8,720 of preferred equity, respectively. The Company earns an 8.0% return on its preferred equity in these joint ventures, which has priority over other distributions.

Schedule of Equity in Earnings of Unconsolidated Real Estate Ventures

Equity in earnings of unconsolidated real estate ventures consists of the following:



	For the Year Ended December 31,
	2018			2017		2016
Equity in earnings of WICNN JV LLC	$	622		$	—	$	—
Equity in earnings of VRS Self Storage, LLC	3,640			3,562		2,919
Equity in earnings of PRISA Self Storage LLC	2,338			2,430		1,912
Equity in earnings of Alan Jathoo JV LLC	(12		)	—		—
Equity in earnings of Extra Space West Two LLC	1,042			1,210		174
Equity in earnings of ESS Bristol Investments LLC	(152		)	—		—
Equity in earnings of Extra Space West One LLC	2,526			2,502		2,269
Equity in earnings of WCOT Self Storage LLC	359			1,033		614
Equity in earnings of Extra Space Northern Properties Six LLC	1,014			918		823
Equity in earnings of Storage Portfolio I LLC	1,886			2,684		2,380
Equity in earnings of Storage Portfolio II JV LLC	79			33		—
Equity in earnings of other minority owned stores	1,110			959		1,804
	$	14,452		$	15,331	$	12,895

Notes Payable and Revolving Lines of Credit (Tables)

12 Months Ended

Dec. 31, 2018

Debt Disclosure [Abstract]

Schedule of Components of Notes Payable

The components of notes payable are summarized as follows:



Notes Payable	December 31, 2018			December 31, 2017			Fixed Rate	Variable Rate	Basis Rate ⁽²⁾	Maturity Dates
Secured fixed rate notes payable ⁽¹⁾	$	2,032,414		$	2,095,495		2.5% - 6.0%			February 2019 - February 2030
Secured variable rate notes payable ⁽¹⁾	834,735			717,979				3.9% - 4.1%	Libor plus 1.4% - 1.6%	May 2019 - August 2028
Unsecured fixed rate notes payable	990,000			600,000			3.4% - 4.4%			January 2024 - July 2028
Unsecured variable rate notes payable	310,000			350,000				3.8%	Libor plus 1.3%	October 2023 - January 2024
Total	4,167,149			3,763,474
Less: unamortized debt issuance costs	(29,936		)	(24,977		)
Total	$	4,137,213		$	3,738,497

⁽¹⁾ The loans are collateralized by mortgages on real estate assets and the assignment of rents.
⁽²⁾ 30-day USD LIBOR

Schedule of Maturities of Notes Payable

The following table summarizes the scheduled maturities of notes payable, excluding available extensions, at December 31, 2018:




2019	$	208,742
2020	699,522
2021	228,015
2022	294,948
2023	915,646
Thereafter	1,820,276
	$	4,167,149

Schedule of Information on Lines of Credit

The following table presents information on the Company’s lines of credit, the proceeds of which are used to repay debt and for general corporate purposes, for the periods indicated:

As of December 31, 2018

Revolving Lines of Credit

Amount Drawn

Capacity

Interest Rate

Origination Date

Maturity

Basis Rate ⁽¹⁾

Credit Line 1 ⁽²⁾

81,000

140,000

4.0%

6/4/2010

7/1/2021

LIBOR plus 1.5%

Credit Line 2 ⁽³⁾⁽⁴⁾

—

650,000

3.6%

12/7/2018

1/29/2023

LIBOR plus 1.1%

81,000

790,000

(1) 30-day USD LIBOR

(2) Secured by mortgages on certain real estate assets. One two-year extension available.

(3) Unsecured. Two six-month extensions available.

(4) Basis Rate as of December 31, 2018. Rate is subject to change based on our consolidated leverage ratio.

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

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+ Details

Derivatives (Tables)

12 Months Ended

Dec. 31, 2018

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule Summarizing Terms of Entity's Derivative Financial Instruments

The following table summarizes the terms of the Company’s 28 derivative financial instruments, which have a total combined notional amount of $2,231,162 as of December 31, 2018:



Hedge Product	Range of Notional Amounts	Strike	Effective Dates	Maturity Dates
Swap Agreements	$4,873 - $267,431	1.13% - 3.87%	2/29/2012 - 12/31/2018	2/28/2019 - 7/12/2025

Schedule of Balance Sheet Classification and Fair Value of Entity's Derivative Financial Instruments

The table below presents the fair value of the Company’s derivative financial instruments as well as their classification on the consolidated balance sheets:



	Asset / Liability Derivatives
	December 31, 2018		December 31, 2017
Derivatives designated as hedging instruments:	Fair Value
Other assets	$	42,324	$	38,365
Other liabilities	$	2,131	$	9

Schedule of Information Relating to Gain (Loss) Recognized on Swap Agreements



	Gain (loss) recognized in OCI For the Year Ended December 31,				Location of amounts reclassified from OCI into income	Gain (loss) reclassified from OCI For the Year Ended December 31,
Type	2018		2017		Location of amounts reclassified from OCI into income	2018		2017			2016
Swap Agreements	$	9,889	$	8,499	Interest expense	$	8,258	$	(8,853	)	$	(18,800	)

- Definition

Tabular disclosure of pertinent information about a derivative or group of derivatives on a disaggregated basis, such as for individual instruments, or small groups of similar instruments. May include a combination of the type of instrument, risks being hedged, notional amount, hedge designation, related hedged item, inception date, maturity date, or other relevant item.

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+ Details

Notes Payable to Trusts (Tables)

12 Months Ended

Dec. 31, 2018

Equity [Abstract]

Schedule of Liabilities and Maximum Exposure to Loss Related to Trusts



	Notes payable to Trusts		Investment Balance		Maximum exposure to loss		Difference
Trust	$	30,928	$	928	$	30,000	$	—

Exchangeable Senior Notes - (Tables)

12 Months Ended

Dec. 31, 2018

Debt Disclosure [Abstract]

Schedule of Information about Carrying Amount of Equity Component, Principal Amount of Liability Component, Unamortized Discount and Net Carrying Amount for Notes



	December 31, 2018			December 31, 2017
Carrying amount of equity component - 2015 Notes	$	22,597		$	22,597
Carrying amount of equity component - 2013 Notes	—			—
Carrying amount of equity components	$	22,597		$	22,597
Principal amount of liability component - 2015 Notes	$	575,000		$	575,000
Principal amount of liability component - 2013 Notes	—			49,259
Unamortized discount - equity component - 2015 Notes	(8,417		)	(12,974		)
Unamortized discount - equity component - 2013 Notes	—			(315		)
Unamortized cash discount - 2013 Notes	—			(74		)
Unamortized debt issuance costs	(4,209		)	(6,620		)
Net carrying amount of liability components	$	562,374		$	604,276

Summary of Amount of Interest Cost Recognized Relating to Contractual Interest Rate and Amortization of Discount on Liability Component of Notes



	For the Year Ended December 31,
	2018		2017		2016
Contractual interest	$	18,106	$	19,303	$	19,483
Amortization of discount	4,687		5,103		4,980
Total interest expense recognized	$	22,793	$	24,406	$	24,463

Summary of Repurchase of Debt

Information about the repurchases is as follows:



	For the Year Ended December 31,
	2018			2017			2016
Principal amount repurchased	$	49,259		$	13,911		$	22,194

Amount allocated to:
Extinguishment of liability component	$	49,019		$	13,692		$	21,363
Reacquisition of equity component	31,251			6,350			13,898
Total consideration paid for repurchase	$	80,270		$	20,042		$	35,261
Exchangeable senior notes repurchased	$	49,259		$	13,911		$	22,194
Extinguishment of liability component	(49,019		)	(13,692		)	(21,363		)
Discount on exchangeable senior notes	(230		)	(184		)	(788		)
Related debt issuance costs	(10		)	(35		)	(43		)
Gain/(loss) on repurchase	$	—		$	—		$	—

Noncontrolling Interests In Operating Partnership and Other Noncontrolling Interests Noncontrolling Interest in Operating Partnership (Tables)

12 Months Ended

Dec. 31, 2018

Noncontrolling Interest [Abstract]

Redeemable Noncontrolling Interest

OP Unit activity is summarized as follows for the periods presented:



	For the Year Ended December 31,
	2018		2017		2016
OP Units redeemed for common stock	35,000		—		23,850
OP Units redeemed for cash	30,000		33,896		6,760
Cash paid for OP Units redeemed	$	2,558	$	2,510	$	506
OP Units issued in conjunction with acquisitions	21,768		90,228		93,569
Value of OP Units issued in conjunction with acquisitions	$	1,877	$	7,618	$	7,247

Stock-Based Compensation - (Tables)

12 Months Ended

Dec. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of Stock Option Activity

A summary of stock option activity is as follows:



Options	Number of Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value as of December 31, 2018
Outstanding at December 31, 2015	572,629		$	24.42
Granted	35,800		85.99
Exercised	(97,855	)	14.75
Outstanding at December 31, 2016	510,574		$	30.60
Exercised	(38,418	)	32.94
Outstanding at December 31, 2017	472,156		$	30.41
Exercised	(54,575	)	21.45
Outstanding at December 31, 2018	417,581		$	31.58	2.78	$24,597

Vested and Expected to Vest	416,567		$	31.46	2.77	$24,587
Ending Exercisable	377,292		$	26.72	2.35	$24,057

Schedule of Weighted Average Assumptions Used to Estimate Fair Value of Awards

The fair value of each option grant is estimated on the date of grant using the Black-Scholes option-pricing model with the following weighted average assumptions:



			For the Year Ended December 31,
			2016
Expected volatility			37.0%
Dividend yield			3.6%
Risk-free interest rate			1.3%
Average expected term (years)			5



	For the Year Ended December 31,
	2018	2017
Intrinsic value	$5,321	$2,630
Compensation cost	$1,873	$840
Risk-free rate	2.37%	1.62%
Volatility	22.6%	21.4%
Expected term (in years)	2.9	2.8
Dividend yield	—%	—%
Unrecognized compensation cost	$2,739	$1,681
Term over which unrecognized compensation cost recognized	2	2

Schedule of Stock Options Outstanding and Exercisable

A summary of stock options outstanding and exercisable as of December 31, 2018, is as follows:



	Options Outstanding				Options Exercisable
Exercise Price	Shares	Weighted Average Remaining Contractual Life	Weighted Average Exercise Price		Shares	Weighted Average Exercise Price
$6.22 - $6.22	139,250	0.13	$	6.22	139,250	$	6.22
$11.59 - $11.59	20,080	1.13	11.59		20,080	11.59
$12.21 - $12.21	77,400	1.18	12.21		77,400	12.21
$19.6 - $28.79	29,469	2.65	23.56		29,469	23.56
$38.4 - $38.4	10,360	4.14	38.4		10,360	38.40
$47.5 - $47.5	17,687	5.13	47.5		17,687	47.50
$65.36 - $65.36	20,395	6.15	65.36		15,297	65.36
$65.45 - $65.45	17,140	6.13	65.45		12,345	65.45
$73.52 - $73.52	50,000	6.58	73.52		37,500	73.52
$85.99 - $85.99	35,800	7.15	85.99		17,904	85.99
	417,581	2.78	$	31.58	377,292	$	26.72

Summary of Company's Employee and Director Share Grant Activity

A summary of the Company’s employee and director share grant activity is as follows:



Restricted Stock Grants	Shares		Weighted-Average Grant-Date Fair Value
Unreleased at December 31, 2015	318,409		$	55.75
Granted	119,931		87.61
Released	(128,808	)	50.05
Cancelled	(9,947	)	67.36
Unreleased at December 31, 2016	299,585		$	70.57
Granted	95,392		74.49
Released	(120,323	)	63.95
Cancelled	(8,179	)	77.25
Unreleased at December 31, 2017	266,475		$	74.76
Granted	85,066		86.14
Released	(116,656	)	72.38
Cancelled	(11,771	)	80.96
Unreleased at December 31, 2018	223,114		$	80.02

Schedule of Nonvested Performance-based Units Activity

A summary of the PSU activity is as follows:



Performance-Based Stock Units	Units	Weighted-Average Grant-Date Fair Value
Unvested at December 31, 2016	—	$	—
Granted	30,071	83.84
Unvested at December 31, 2017	30,071	$	83.84
Granted	28,735	96.19
Unvested at December 31, 2018	58,806	$	89.87

Income Taxes - (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Summarized Statement of Components of Income Tax Provision

The income tax provision for the years ended December 31, 2018, 2017 and 2016, is comprised of the following components:



	For the Year Ended December 31, 2018
	Federal			State			Total
Current expense	$	9,136		$	2,426		$	11,562
Tax credits/true-up	(5,841		)	(175		)	(6,016		)
Change in deferred expense/(benefit)	3,730			(32		)	3,698
Total tax expense	$	7,025		$	2,219		$	9,244



	For the Year Ended December 31, 2017
	Federal			State			Total
Current expense	$	5,677		$	1,662		$	7,339
Tax credits/true-up	(5,573		)	(383		)	(5,956		)
Change in deferred expense	1,700			542			2,242
Total tax expense	$	1,804		$	1,821		$	3,625



	For the Year Ended December 31, 2016
	Federal			State			Total
Current expense	$	14,627		$	2,368		$	16,995
Tax credits/true-up	(312		)	—			(312		)
Change in deferred benefit	(369		)	(467		)	(836		)
Total tax expense	$	13,946		$	1,901		$	15,847

Schedule of Reconciliation of Statutory Income Tax Provisions to the Effective Income Tax Provisions

A reconciliation of the statutory income tax provisions to the effective income tax provisions for the periods indicated is as follows:



	For the Year Ended December 31,
	2018					2017					2016
Expected tax at statutory rate	$	95,828		21.0	%	$	186,274		35.0	%	$	144,708		35.0	%
Non-taxable REIT income	(83,022		)	(18.2	)%	(170,811		)	(32.1	)%	(131,112		)	(31.7	)%
State and local tax expense - net of federal benefit	2,385			0.5	%	2,306			0.4	%	2,399			0.6	%
Change in valuation allowance	(1,052		)	(0.2	)%	159			—	%	(845		)	(0.2	)%
Tax credits/true-up	(6,016		)	(1.3	)%	(5,956		)	(1.1	)%	(312		)	(0.1	)%
Remeasurement of deferred balances	—			—	%	(8,460		)	(1.6	)%	—			—	%
Miscellaneous	1,121			0.2	%	113			—	%	1,009			0.2	%
Total provision	$	9,244		2.0	%	$	3,625		0.6	%	$	15,847		3.8	%

Schedule of Major Sources of Temporary Differences Stated at their Deferred Tax Effects

The major sources of temporary differences stated at their deferred tax effects are as follows:



	December 31, 2018			December 31, 2017
Deferred tax liabilities:
Fixed assets	$	(20,907	)	$	(15,271	)
Other	(96		)	(108		)
State deferred taxes	(3,076		)	(2,822		)
Total deferred tax liabilities	(24,079		)	(18,201		)

Deferred tax assets:
Captive insurance subsidiary	324			252
Accrued liabilities	1,772			873
Stock compensation	1,604			1,287
Solar credit	—			43
Other	53			57
SmartStop TRS	219			219
State deferred taxes	7,196			7,802
Total deferred tax assets	11,168			10,533

Valuation allowance	(3,872		)	(4,924		)

Net deferred income tax liabilities	$	(16,783	)	$	(12,592	)

Segment Information - (Tables)

12 Months Ended

Dec. 31, 2018

Segment Reporting [Abstract]

Schedule of Financial Information of Business Segments

Financial information for the Company’s business segments is set forth below:



	Year Ended December 31,
	2018			2017			2016
Revenues:
Self-Storage Operations	$	1,039,340		$	967,229		$	864,742
Tenant Reinsurance	115,507			98,401			87,291
Total segment revenues	1,154,847			1,065,630			$	952,033

Operating expenses:
Self-Storage Operations	$	291,695		$	271,974		$	250,005
Tenant Reinsurance	25,707			19,173			15,555
Total segment operating expenses	$	317,402		$	291,147		$	265,560

Net operating income:
Self-Storage Operations	747,645			695,255			$	614,737
Tenant Reinsurance	89,800			79,228			71,736
Total segment net operating income:	$	837,445		$	774,483		$	686,473

Total segment net operating income	$	837,445		$	774,483		$	686,473
Other components of net income (loss):
Property management fees and other income	41,757			39,379			39,842
General and administrative expense	(81,256		)	(78,961		)	(81,806		)
Depreciation and amortization expense	(209,050		)	(193,296		)	(182,560		)
Acquisition and other related costs⁽¹⁾	—			—			(12,111		)
Gain on real estate transactions, earnout from prior acquisitions and impairment of real estate	30,807			112,789			8,465
Interest expense	(178,436		)	(153,511		)	(133,479		)
Non-cash interest expense related to the amortization of discount on equity component of exchangeable senior notes	(4,687		)	(5,103		)	(4,980		)
Interest income	5,292			6,736			10,998
Equity in earnings of unconsolidated real estate ventures	14,452			15,331			12,895
Equity in earnings of unconsolidated real estate ventures - gain on sale of real estate assets and purchase of partners' interests	—			—			69,199
Income tax expense	(9,244		)	(3,625		)	(15,847		)
Net income	$	447,080		$	514,222		$	397,089

(1) Beginning January 1, 2017, acquisition related costs have been capitalized due to the adoption of ASU 2017-01, "Business Combinations (Topic 805): Clarifying the Definition of a Business."

Commitments and Contingencies - (Tables)

12 Months Ended

Dec. 31, 2018

Commitments and Contingencies Disclosure [Abstract]

Schedule of Future Minimum Rental Payments Under Non-Cancelable Operating Lease

At December 31, 2018, future minimum rental payments under these non-cancelable operating leases were as follows (unaudited):



Less than 1 year	$	8,203
Year 2	8,307
Year 3	8,137
Year 4	7,837
Year 5	7,021
Thereafter	111,653
	$	151,158

Supplementary Quarterly Financial Data (Unaudited) - (Tables)

12 Months Ended

Dec. 31, 2018

Quarterly Financial Information Disclosure [Abstract]

Schedule of Supplementary Quarterly Financial Data

SUPPLEMENTARY QUARTERLY FINANCIAL DATA (UNAUDITED)



	For the Three Months Ended
	March 31, 2018		June 30, 2018		September 30, 2018		December 31, 2018
Revenues	$	285,485	$	296,813	$	306,953	$	307,353
Cost of operations	151,573		152,097		153,362		150,676
Revenues less cost of operations	$	133,912	$	144,716	$	153,591	$	156,677
Net income	$	95,430	$	102,713	$	139,687	$	109,250
Net income attributable to common stockholders	$	88,256	$	95,153	$	130,418	$	101,462
Earnings per common share—basic	$	0.70	$	0.75	$	1.03	$	0.80
Earnings per common share—diluted	$	0.70	$	0.75	$	1.02	$	0.80
	For the Three Months Ended
	March 31, 2017		June 30, 2017		September 30, 2017		December 31, 2017
Revenues	$	263,008	$	276,003	$	284,156	$	281,842
Cost of operations	138,805		139,596		144,275		140,728
Revenues less cost of operations	$	124,203	$	136,407	$	139,881	$	141,114
Net income	$	89,734	$	94,098	$	101,075	$	229,315
Net income attributable to common stockholders	$	82,282	$	87,006	$	93,742	$	215,983
Earnings per common share—basic	$	0.65	$	0.69	$	0.74	$	1.71
Earnings per common share—diluted	$	0.64	$	0.69	$	0.74	$	1.69

Description of Business (Details)	Dec. 31, 2018 store state
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of storage facilities in which the entity had equity interests	1,111
Number of stores managed for third parties	536
Number of stores owned and/or managed	1,647
Number of states in which storage facilities are located \| state	39

Summary of Significant Accounting Policies - Basis of Presentation (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Investments in unconsolidated real estate ventures	$ 125,326	$ 75,907
Cash distributions in unconsolidated real estate ventures	$ 45,197	5,816
Reclassification
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Investments in unconsolidated real estate ventures		(5,816)
Cash distributions in unconsolidated real estate ventures		$ 5,816

Summary of Significant Accounting Policies - Variable Interest Entities (Details)	Dec. 31, 2018 entity
Accounting Policies [Abstract]
Number of nonconsolidated VIEs to which Operating Partnership has notes payable (in number of entities)	1

Summary of Significant Accounting Policies - Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - Recurring $ in Thousands	Dec. 31, 2018 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets - Cash Flow Hedge Swap Agreements	$ 42,324
Other liabilities - Cash Flow Hedge Swap Agreements	(2,131)
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets - Cash Flow Hedge Swap Agreements	0
Other liabilities - Cash Flow Hedge Swap Agreements	0
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets - Cash Flow Hedge Swap Agreements	42,324
Other liabilities - Cash Flow Hedge Swap Agreements	(2,131)
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets - Cash Flow Hedge Swap Agreements	0
Other liabilities - Cash Flow Hedge Swap Agreements	$ 0

Summary of Significant Accounting Policies - Schedule of Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value
Fair Value of Financial Instruments [Line Items]
Notes receivable from Preferred and Common Operating Partnership unit holders	$ 115,467	$ 113,683
Fixed rate notes receivable	0	20,942
Fixed rate notes payable and notes payable to trusts	2,985,731	2,774,242
Exchangeable senior notes	620,149	719,056
Carrying Value
Fair Value of Financial Instruments [Line Items]
Notes receivable from Preferred and Common Operating Partnership unit holders	119,735	120,230
Fixed rate notes receivable	0	20,608
Fixed rate notes payable and notes payable to trusts	3,022,414	2,815,085
Exchangeable senior notes	$ 575,000	$ 624,259

Summary of Significant Accounting Policies - Real Estate Assets (Details)	12 Months Ended
	Dec. 31, 2018 store
Property, Plant and Equipment [Line Items]
Number of properties whereby leases cannot be classified as ground or building leases	3
Number of properties whereby leases have been assumed at rates lower than the current market rates	8
Buildings, improvements and other intangibles \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Buildings, improvements and other intangibles \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	39 years

Summary of Significant Accounting Policies - Other Assets (Details) - Equipment and fixtures	12 Months Ended
	Dec. 31, 2018
Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years

Summary of Significant Accounting Policies - Risk Management and Use of Financial Instruments (Details)	12 Months Ended
	Dec. 31, 2018 item
Accounting Policies [Abstract]
Number of main components of economic risk	3

Summary of Significant Accounting Policies - Revenue and Expense Recognition (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) claim	Dec. 31, 2017 claim	Dec. 31, 2016 claim
Disaggregation of Revenue [Line Items]
Minimum amount of insurance coverage	$ 2,000
Maximum amount of insurance coverage	10,000
Average amount of insurance coverage	$ 2,900
Number of claims made \| claim	7,870	5,671	4,055
Management Services Agreements (MSA) \| Minimum
Disaggregation of Revenue [Line Items]
Contract term	3 years
Management Services Agreements (MSA) \| Maximum
Disaggregation of Revenue [Line Items]
Contract term	5 years

Summary of Significant Accounting Policies - Schedule of Unpaid Claims Liability (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Tenant Reinsurance Claims:
Unpaid claims liability at beginning of year	$ 5,167	$ 3,896	$ 3,908
Claims and claim adjustment expense for claims incurred in the current year	15,800	11,700	7,250
Claims and claim adjustment expense (benefit) for claims incurred in the prior years	107	(203)	87
Payments for current year claims	(11,010)	(8,895)	(5,423)
Payments for prior year claims	(2,738)	(1,331)	(1,926)
Unpaid claims liability at the end of the year	$ 7,326	$ 5,167	$ 3,896

Summary of Significant Accounting Policies - Advertising Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Advertising expense	$ 16,153	$ 14,410	$ 12,867

Summary of Significant Accounting Policies - Income Taxes (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
REIT taxable income required to be distributed (as a percent)	90.00%
Percentage of all distributions to stockholders which qualified as a return of capital	0.00%
Unrecognized tax benefits	$ 0	$ 0
Interest or penalties related to uncertain tax provisions	$ 0	$ 0

Summary of Significant Accounting Policies - Earnings Per Common Share (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2015	Jun. 21, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Average share price (in dollars per share)	$ 90.30
Exchangeable senior notes	$ 562,374,000	$ 604,276,000
Series A Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Instruments to be settled in cash (at least)	$ 101,700,000
Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per common share (in shares)	36,075	45,286	88,552
2013 Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Fixed interest rate					2.375%
Shares related to the Notes included in the computation for diluted earnings per share (in shares)		344,430
2013 Notes \| Operating Partnership
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares related to the Notes included in the computation for diluted earnings per share (in shares)			309,730
2015 Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Exchangeable senior notes	$ 575,000,000
Fixed interest rate	3.125%			3.125%
Exchange price (in dollars per share)	$ 92.80
Shares related to the Notes included in the computation for diluted earnings per share (in shares)	0	0	0

Summary of Significant Accounting Policies - Schedule of Antidilutive Shares Excluded from Computation of Earnings Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Equivalent Shares (if converted) (in shares)	1,795,632	910,309	7,846,519
Common OP Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Equivalent Shares (if converted) (in shares)	0	0	5,564,631
Series A Units (Variable Only)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Equivalent Shares (if converted) (in shares)	0	0	875,480
Series B Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Equivalent Shares (if converted) (in shares)	464,033	533,174	499,966
Series C Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Equivalent Shares (if converted) (in shares)	312,075	377,135	353,646
Series D Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Equivalent Shares (if converted) (in shares)	1,019,524	0	552,796

Summary of Significant Accounting Policies - Schedule of Computation of Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Net income attributable to common stockholders	$ 101,462	$ 130,418	$ 95,153	$ 88,256	$ 215,983	$ 93,742	$ 87,006	$ 82,282	$ 415,289	$ 479,013	$ 366,127
Earnings and dividends allocated to participating securities									(723)	(975)	(792)
Earnings for basic computations									414,566	478,038	365,335
Earnings and dividends allocated to participating securities									723	0	792
Income allocated to noncontrolling interest - Preferred Operating Partnership Units and Operating Partnership Units									22,831	30,088	0
Fixed component of income allocated to noncontrolling interest - Preferred Operating Partnership (Series A Units)									(2,288)	(3,119)	0
Net income for diluted computations									$ 435,832	$ 505,007	$ 366,127
Weighted average common shares outstanding:
Average number of common shares outstanding - basic (in shares)									126,087,487	125,967,831	125,087,554
OP Units (in shares)									5,675,547	5,590,831	0
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Unvested restricted stock awards included for treasury stock method (in shares)									244,215	0	299,585
Shares related to exchangeable senior notes and dilutive stock options (in shares)									276,304	640,068	560,937
Average number of common shares outstanding - diluted (in shares)									133,159,033	134,155,771	125,948,076
Earnings per common share
Basic (in dollars per share)	$ 0.80	$ 1.03	$ 0.75	$ 0.70	$ 1.71	$ 0.74	$ 0.69	$ 0.65	$ 3.29	$ 3.79	$ 2.92
Diluted (in dollars per share)	$ 0.80	$ 1.02	$ 0.75	$ 0.70	$ 1.69	$ 0.74	$ 0.69	$ 0.64	$ 3.27	$ 3.76	$ 2.91
Series A Units
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Series A&D Units (in shares)									875,480	875,480	0
Series D Units
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Series A&D Units (in shares)									0	1,081,561	0

Summary of Significant Accounting Policies - Recently Issued Accounting Standards (Details) $ in Thousands	Jan. 01, 2019 USD ($)	Dec. 31, 2018 lease
ASU 2016-02 \| Estimated \| Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease assets	$ 90,000
Lease liabilities	90
ASU 2016-02 \| Estimated \| Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease assets	110,000
Lease liabilities	$ 110
Operating ground leases
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of operating ground leases \| lease		23
Corporate facility leases
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of operating ground leases \| lease		2

Real Estate Assets - Schedule of Components of Real Estate Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Real Estate Properties [Line Items]
Real estate assets, at cost	$ 8,707,847	$ 8,158,741
Less: accumulated depreciation and amortization	(1,262,438)	(1,060,060)
Net operating real estate assets	7,445,409	7,098,681
Real estate under development/redevelopment	46,422	33,750
Net real estate assets	7,491,831	7,132,431	$ 6,770,447
Real estate assets held for sale included in net real estate assets	13,032	10,276
Land - operating
Real Estate Properties [Line Items]
Real estate assets, at cost	1,825,133	1,731,915
Land - development
Real Estate Properties [Line Items]
Real estate assets, at cost	7,359	13,246
Buildings, improvements and other intangibles
Real Estate Properties [Line Items]
Real estate assets, at cost	6,743,355	6,286,762
Intangible assets - tenant relationships
Real Estate Properties [Line Items]
Real estate assets, at cost	119,557	114,375
Intangible lease rights
Real Estate Properties [Line Items]
Real estate assets, at cost	$ 12,443	$ 12,443

Real Estate Assets - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) store land_parcel	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Real Estate [Abstract]
Number of operating stores classified as held for sale \| store	1
Number of parcels of land classified as held for sale \| land_parcel	1
Average period that a tenant is expected to utilize the facility	18 months
Amortization related to the tenant relationships and lease rights	$ 9,050	$ 14,349	$ 21,133
Real Estate Properties [Line Items]
Intangible assets, accumulated amortization	$ 121,238	$ 112,347
Minimum
Real Estate Properties [Line Items]
Remaining amortization period	1 year
Maximum
Real Estate Properties [Line Items]
Remaining amortization period	43 years

Property Acquisitions and Dispositions - Acquisitions of Operating Stores (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018 USD ($) store shares	Sep. 30, 2018 USD ($) store shares	Jun. 30, 2018 USD ($) store shares	Mar. 31, 2018 USD ($) store shares	Dec. 31, 2017 USD ($) store shares	Sep. 30, 2017 USD ($) store shares	Jun. 30, 2017 USD ($) store shares	Mar. 31, 2017 USD ($) store shares	Dec. 31, 2018 USD ($) store shares	Dec. 31, 2017 USD ($) store shares
Real Estate [Abstract]
Number of stores \| store	6	6	17	5	37	4	3	2	34	46
Total	$ 74,852	$ 74,694	$ 237,284	$ 70,787	$ 535,299	$ 31,966	$ 34,641	$ 25,556	$ 457,617	$ 627,462
Cash Paid	74,868	71,989	148,650	70,171	502,845	29,919	16,608	25,541	365,678	574,913
Loan Assumed	0	0	87,500	0	14,592	0	9,463	0	87,500	24,055
Non- controlling interests	0	0	0	0	(1,812)	0	1,827	0	0	15
Investments in Real Estate Ventures	0	0	(1,024)	489	12,957	0	0	0	(535)	12,957
Net Liabilities/ (Assets) Assumed	(16)	2,705	281	127	1,099	47	(67)	15	3,097	1,094
Value of OP Units Issued	$ 0	$ 0	$ 1,877	$ 0	$ 5,618	$ 2,000	$ 6,810	$ 0	$ 1,877	$ 14,428
Number of units issued (in shares) \| shares	0	0	21,768	0	64,708	25,520	272,400	0	21,768	362,628
Real estate assets	$ 74,852	$ 74,694	$ 237,284	$ 70,787	$ 535,299	$ 31,966	$ 34,641	$ 25,556	$ 457,617	$ 627,462
Number of stores acquired, previously held noncontrolling interest \| store									15
Number of stores acquired, previously held equity interest \| store										7

Property Acquisitions and Dispositions - Additional Information (Details) $ in Thousands							1 Months Ended	6 Months Ended	12 Months Ended
	Aug. 16, 2018 USD ($)	Nov. 30, 2017 USD ($) store	Sep. 13, 2017 USD ($)	Jul. 26, 2016 USD ($)	Apr. 20, 2016 USD ($) store	Apr. 01, 2016 USD ($) shares	Dec. 31, 2014 store	Jun. 30, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Property Acquisitions [Line Items]
Proceeds from sale of real estate assets, investments in real estate ventures and other assets									$ 52,458	$ 312,165	$ 60,813
Acquisition of Stores in New Jersey and Virginia
Property Acquisitions [Line Items]
Number of stores acquired \| store							5
Increase in payments due to sellers											$ 4,284
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Disposal of California Store
Property Acquisitions [Line Items]
Proceeds from sale of real estate assets, investments in real estate ventures and other assets	$ 40,235
Gain (loss) on disposition of assets	$ 30,671
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Disposal of 36 Stores Located in Various States
Property Acquisitions [Line Items]
Proceeds from sale of real estate assets, investments in real estate ventures and other assets		$ 295,000
Gain (loss) on disposition of assets		$ 118,776
Number of stores sold \| store		36
Percentage of gain received on disposition		90.00%
Percentage of gain deferred on disposition		10.00%
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Disposal of New York Land
Property Acquisitions [Line Items]
Proceeds from sale of real estate assets, investments in real estate ventures and other assets			$ 19,000
Gain (loss) on disposition of assets								$ (3,500)
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Disposal of Indiana Store
Property Acquisitions [Line Items]
Proceeds from sale of real estate assets, investments in real estate ventures and other assets				$ 4,447
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Disposal of Ohio and Indiana Stores
Property Acquisitions [Line Items]
Proceeds from sale of real estate assets, investments in real estate ventures and other assets					$ 17,555
Gain (loss) on disposition of assets					$ 11,265
Number of stores sold \| store					7
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Disposal of Texas Store
Property Acquisitions [Line Items]
Gain (loss) on disposition of assets						$ 93
OP Units received on disposal (in shares) \| shares						85,452
Value of OP Units received on disposal						$ 7,689
Storage Portfolio II JV LLC
Property Acquisitions [Line Items]
Equity ownership %		10.00%							10.00%

Investments in Unconsolidated Real Estate Ventures - Schedule of Investments in Unconsolidated Real Estate Ventures (Details) $ in Thousands		2 Months Ended	3 Months Ended								12 Months Ended
	Apr. 30, 2018 USD ($) store	Feb. 26, 2019 USD ($) store	Dec. 31, 2018 USD ($) store property joint_venture	Sep. 30, 2018 USD ($) store	Jun. 30, 2018 USD ($) store	Mar. 31, 2018 USD ($) store	Dec. 31, 2017 USD ($) store	Sep. 30, 2017 USD ($) store	Jun. 30, 2017 USD ($) store	Mar. 31, 2017 USD ($) store	Dec. 31, 2018 USD ($) store property joint_venture	Dec. 31, 2017 USD ($) store	Nov. 30, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Number of Stores \| property			229								229
Net Investments in and Cash distributions in unconsolidated real estate ventures			$ 80,129				$ 70,091				$ 80,129	$ 70,091
Number of joint ventures, not significant for separate disclosure \| joint_venture			17								17
Number of stores acquired \| store			6	6	17	5	37	4	3	2	34	46
Cash paid to acquire properties			$ 74,868	$ 71,989	$ 148,650	$ 70,171	$ 502,845	$ 29,919	$ 16,608	$ 25,541	$ 365,678	$ 574,913
Loan assumed			$ 0	$ 0	$ 87,500	$ 0	$ 14,592	$ 0	$ 9,463	$ 0	$ 87,500	$ 24,055
Minimum
Schedule of Equity Method Investments [Line Items]
Equity Ownership %			10.00%				10.00%				10.00%	10.00%		20.00%
Maximum
Schedule of Equity Method Investments [Line Items]
Equity Ownership %			50.00%				25.00%				50.00%	25.00%		50.00%
WICNN JV LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores \| property			7								7
Equity Ownership %			10.00%								10.00%
Excess Profit %			25.00%								25.00%
Net Investments in and Cash distributions in unconsolidated real estate ventures			$ 26,885				$ 0				$ 26,885	$ 0
VRS Self Storage, LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores \| property			16								16
Equity Ownership %			45.00%								45.00%
Excess Profit %			54.00%								54.00%
Net Investments in and Cash distributions in unconsolidated real estate ventures			$ 18,281				19,467				$ 18,281	19,467
PRISA Self Storage LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores \| property			85								85
Equity Ownership %			4.00%								4.00%
Excess Profit %			4.00%								4.00%
Net Investments in and Cash distributions in unconsolidated real estate ventures			$ 9,334				9,638				$ 9,334	9,638
Alan Jathoo JV LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores \| property			9								9
Equity Ownership %			10.00%								10.00%
Excess Profit %			10.00%								10.00%
Net Investments in and Cash distributions in unconsolidated real estate ventures			$ 8,180				0				$ 8,180	0
Extra Space West Two LLC (1)
Schedule of Equity Method Investments [Line Items]
Number of Stores \| property			5								5
Equity Ownership %			5.00%								5.00%
Excess Profit %			40.00%								40.00%
Net Investments in and Cash distributions in unconsolidated real estate ventures			$ 3,818				3,939				$ 3,818	3,939
ESS Bristol Investments LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores \| property			7								7
Equity Ownership %			10.00%								10.00%
Excess Profit %			28.00%								28.00%
Net Investments in and Cash distributions in unconsolidated real estate ventures			$ 2,331				1,258				$ 2,331	1,258
WCOT Self Storage LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores \| property			0								0
Equity Ownership %			5.00%								5.00%
Excess Profit %			20.00%								20.00%
Net Investments in and Cash distributions in unconsolidated real estate ventures			$ 0				(357)				$ 0	(357)
Number of stores acquired \| store	14
Cash paid to acquire properties	$ 115,797
Loan assumed	$ 87,500
Extra Space West One LLC (1)
Schedule of Equity Method Investments [Line Items]
Number of Stores \| property			7								7
Equity Ownership %			5.00%								5.00%
Excess Profit %			40.00%								40.00%
Net Investments in and Cash distributions in unconsolidated real estate ventures			$ (1,038)				(900)				$ (1,038)	(900)
Extra Space Northern Properties Six LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores \| property			10								10
Equity Ownership %			10.00%								10.00%
Excess Profit %			35.00%								35.00%
Net Investments in and Cash distributions in unconsolidated real estate ventures			$ (1,700)				(1,279)				$ (1,700)	(1,279)
Storage Portfolio II JV LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores \| property			36								36
Equity Ownership %			10.00%								10.00%		10.00%
Excess Profit %			30.00%								30.00%
Net Investments in and Cash distributions in unconsolidated real estate ventures			$ (4,233)				(3,140)				$ (4,233)	(3,140)
Storage Portfolio I LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores \| property			24								24
Equity Ownership %			34.00%								34.00%
Excess Profit %			49.00%								49.00%
Net Investments in and Cash distributions in unconsolidated real estate ventures			$ (38,129)				11,495				$ (38,129)	11,495
Other minority owned stores
Schedule of Equity Method Investments [Line Items]
Number of Stores \| property			23								23
Net Investments in and Cash distributions in unconsolidated real estate ventures			$ 56,400				$ 29,970				$ 56,400	$ 29,970
Other minority owned stores \| Minimum
Schedule of Equity Method Investments [Line Items]
Equity Ownership %			10.00%								10.00%
Excess Profit %			19.00%								19.00%
Other minority owned stores \| Maximum
Schedule of Equity Method Investments [Line Items]
Equity Ownership %			50.00%								50.00%
Excess Profit %			50.00%								50.00%
Extra Space West One LLC and Extra Space Two LLC \| Subsequent Event
Schedule of Equity Method Investments [Line Items]
Number of stores acquired \| store		12
Cash paid to acquire properties		$ 172,515
Loan assumed		$ 17,157

Investments in Unconsolidated Real Estate Ventures - New Unconsolidated Joint Ventures (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) store JointVenture	Dec. 31, 2017 USD ($) store	Dec. 31, 2016 USD ($) store
Schedule of Equity Method Investments [Line Items]
Number of Stores \| store	28	39	8
Investment in new stores	$ 63,723	$ 13,341	$ 26,387
Number of new joint ventures with preferred equity investment \| JointVenture	2
Minimum
Schedule of Equity Method Investments [Line Items]
Equity ownership %	10.00%	10.00%	20.00%
Maximum
Schedule of Equity Method Investments [Line Items]
Equity ownership %	50.00%	25.00%	50.00%
WICNN JV LLC
Schedule of Equity Method Investments [Line Items]
Equity ownership %	10.00%
Joint venture preferred equity investment	$ 22,734
Joint venture preferred equity investment return percentage	8.00%
GFV JV, LLC
Schedule of Equity Method Investments [Line Items]
Joint venture preferred equity investment	$ 8,720
Joint venture preferred equity investment return percentage	8.00%

Investments in Unconsolidated Real Estate Ventures - Schedule of Equity in Earnings of Unconsolidated Real Estate Ventures (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Equity in earnings	$ 14,452	$ 15,331	$ 12,895
WICNN JV LLC
Schedule of Equity Method Investments [Line Items]
Equity in earnings	622	0	0
VRS Self Storage, LLC
Schedule of Equity Method Investments [Line Items]
Equity in earnings	3,640	3,562	2,919
PRISA Self Storage LLC
Schedule of Equity Method Investments [Line Items]
Equity in earnings	2,338	2,430	1,912
Alan Jathoo JV LLC
Schedule of Equity Method Investments [Line Items]
Equity in earnings	(12)	0	0
Extra Space West Two LLC (1)
Schedule of Equity Method Investments [Line Items]
Equity in earnings	1,042	1,210	174
ESS Bristol Investments LLC
Schedule of Equity Method Investments [Line Items]
Equity in earnings	(152)	0	0
Extra Space West One LLC (1)
Schedule of Equity Method Investments [Line Items]
Equity in earnings	2,526	2,502	2,269
WCOT Self Storage LLC
Schedule of Equity Method Investments [Line Items]
Equity in earnings	359	1,033	614
Extra Space Northern Properties Six LLC
Schedule of Equity Method Investments [Line Items]
Equity in earnings	1,014	918	823
Storage Portfolio I LLC
Schedule of Equity Method Investments [Line Items]
Equity in earnings	1,886	2,684	2,380
Storage Portfolio II JV LLC
Schedule of Equity Method Investments [Line Items]
Equity in earnings	79	33	0
Other minority owned stores
Schedule of Equity Method Investments [Line Items]
Equity in earnings	$ 1,110	$ 959	$ 1,804

Investments in Unconsolidated Real Estate Ventures - Additional Information (Details) $ in Thousands					3 Months Ended								12 Months Ended
	Apr. 30, 2018 USD ($) store	Nov. 17, 2016 USD ($) store	Sep. 16, 2016 USD ($) store	Feb. 02, 2016 USD ($) store	Dec. 31, 2018 USD ($) store	Sep. 30, 2018 USD ($) store	Jun. 30, 2018 USD ($) store	Mar. 31, 2018 USD ($) store	Dec. 31, 2017 USD ($) store	Sep. 30, 2017 USD ($) store	Jun. 30, 2017 USD ($) store	Mar. 31, 2017 USD ($) store	Dec. 31, 2018 USD ($) store	Dec. 31, 2017 USD ($) store	Apr. 25, 2016	Apr. 24, 2016
Schedule of Equity Method Investments [Line Items]
Cash paid to acquire properties					$ 74,868	$ 71,989	$ 148,650	$ 70,171	$ 502,845	$ 29,919	$ 16,608	$ 25,541	$ 365,678	$ 574,913
Loan assumed					$ 0	$ 0	$ 87,500	$ 0	$ 14,592	$ 0	$ 9,463	$ 0	$ 87,500	$ 24,055
Number of stores acquired \| store					6	6	17	5	37	4	3	2	34	46
Amortization amount of excess purchase price included in equity earnings					$ 27,867								$ 27,867
Amortization period of excess purchase price included in equity earnings													40 years
Properties acquired September 2016
Schedule of Equity Method Investments [Line Items]
Fair value of stores purchased			$ 248,530
WCOT Self Storage LLC
Schedule of Equity Method Investments [Line Items]
Cash paid to acquire properties	$ 115,797
Loan assumed	$ 87,500
Number of stores acquired \| store	14
Equity ownership %					5.00%								5.00%
ESS WCOT LLC
Schedule of Equity Method Investments [Line Items]
Number of acquired stores \| store		11
Equity ownership %		5.00%
Percentage interests acquired		95.00%
Net carrying amount of properties distributed		$ 68,814
Payment to acquire joint venture interests		$ 153,304
Ownership percentage after transaction		100.00%
Fair value of investment prior to acquisition of additional interest		$ 8,119
Gain recorded as a result of remeasuring fair value of existing equity interest		4,651
Fair value of stores purchased		$ 161,072
ESS PRISA II LLC
Schedule of Equity Method Investments [Line Items]
Number of acquired stores \| store			23
Equity ownership %			4.40%
Number of stores owned \| store														42
Ownership percentage sold			4.42%
Carrying value of investment prior to acquisition			$ 3,912
Realized gain on sale			30,846
ESS PRISA II LLC \| Prudential Real Estate and Affiliates
Schedule of Equity Method Investments [Line Items]
Proceeds from sale of interest			34,758
Extra Space Properties 131 LLC
Schedule of Equity Method Investments [Line Items]
Net carrying amount of properties distributed			$ 4,326
Ownership percentage after transaction			100.00%
Fair value of investment prior to acquisition of additional interest			$ 10,988
Gain recorded as a result of remeasuring fair value of existing equity interest			$ 6,778
Number of transferred stores \| store			23
Extra Space Properties 131 LLC \| Prudential Real Estate and Affiliates
Schedule of Equity Method Investments [Line Items]
Percentage interests acquired			95.60%
Payment to acquire joint venture interests			$ 238,679
ESS PRISA LLC and ESS PRISA II LLC
Schedule of Equity Method Investments [Line Items]
Unconsolidated joint ventures excess profit participation percentage forfeited															17.00%
ESS PRISA LLC
Schedule of Equity Method Investments [Line Items]
Equity ownership %															4.00%	2.00%
ESS Prisa II LLC
Schedule of Equity Method Investments [Line Items]
Equity ownership %															4.40%	2.00%
VRS Self Storage LLC
Schedule of Equity Method Investments [Line Items]
Number of acquired stores \| store				6
Equity ownership %				45.00%
Extra Space Properties 122 LLC
Schedule of Equity Method Investments [Line Items]
Number of acquired stores \| store				6
Net carrying amount of properties distributed				$ 17,261
Ownership percentage after transaction				100.00%
Fair value of investment prior to acquisition of additional interest				$ 44,184
Gain recorded as a result of remeasuring fair value of existing equity interest				26,923
Fair value of stores purchased				$ 98,082
Number of transferred stores \| store				6
Extra Space Properties 122 LLC \| Prudential Real Estate and Affiliates
Schedule of Equity Method Investments [Line Items]
Percentage interests acquired				55.00%
Payment to acquire joint venture interests				$ 53,940

Notes Payable and Revolving Lines of Credit - Schedule of Components of Notes Payable (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Notes payable, net	$ 4,137,213	$ 3,738,497
Notes Payable
Debt Instrument [Line Items]
Total	4,167,149	3,763,474
Unamortized debt issuance costs	(29,936)	(24,977)
Notes payable, net	4,137,213	3,738,497
Notes Payable \| Secured notes payable
Debt Instrument [Line Items]
Fixed rate notes payable	2,032,414	2,095,495
Variable rate notes payable	$ 834,735	717,979
Notes Payable \| Secured notes payable \| Minimum
Debt Instrument [Line Items]
Fixed Rate	2.50%
Variable Rate	3.90%
Notes Payable \| Secured notes payable \| Maximum
Debt Instrument [Line Items]
Fixed Rate	6.00%
Variable Rate	4.10%
Notes Payable \| Secured notes payable \| LIBOR \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	1.40%
Notes Payable \| Secured notes payable \| LIBOR \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	1.60%
Notes Payable \| Unsecured notes payable
Debt Instrument [Line Items]
Fixed rate notes payable	$ 990,000	600,000
Variable rate notes payable	$ 310,000	$ 350,000
Variable Rate	3.80%
Notes Payable \| Unsecured notes payable \| Minimum
Debt Instrument [Line Items]
Fixed Rate	3.40%
Notes Payable \| Unsecured notes payable \| Maximum
Debt Instrument [Line Items]
Fixed Rate	4.40%
Notes Payable \| Unsecured notes payable \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.30%

Notes Payable and Revolving Lines of Credit - Schedule of Maturities of Notes Payable (Details) - Notes Payable - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
2019	$ 208,742
2020	699,522
2021	228,015
2022	294,948
2023	915,646
Thereafter	1,820,276
Total	$ 4,167,149	$ 3,763,474

Notes Payable and Revolving Lines of Credit - Schedule of Information on Lines of Credit (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) extension	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Amount Drawn	$ 81,000,000	$ 94,000,000
Capacity	790,000,000
Credit Line 1
Debt Instrument [Line Items]
Amount Drawn	81,000,000
Capacity	$ 140,000,000
Interest Rate	4.00%
Number of extensions available \| extension	1
Extension term	2 years
Credit Line 2
Debt Instrument [Line Items]
Amount Drawn	$ 0
Capacity	$ 650,000,000
Interest Rate	3.60%
Number of extensions available \| extension	2
Extension term	6 months
LIBOR \| Credit Line 1
Debt Instrument [Line Items]
Basis spread on variable rate	1.50%
LIBOR \| Credit Line 2
Debt Instrument [Line Items]
Basis spread on variable rate	1.10%

Notes Payable and Revolving Lines of Credit - Additional Information (Details)	Dec. 07, 2018 USD ($) extension	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 790,000,000
Line of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 1,350,000,000.00
Increase limit	$ 2,000,000,000.0
Number of extension options \| extension	2
Extension term	6 months
Line of Credit \| Base rate
Debt Instrument [Line Items]
Basis spread on variable rate	0.00%
Line of Credit \| Base rate \| Based on Company's Consolidated Leverage Ratio and type of loan \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	0.05%
Line of Credit \| Base rate \| Based on Company's Consolidated Leverage Ratio and type of loan \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	0.70%
Line of Credit \| Base rate \| If Company elects to use alternative rates based on specified investment grade rating \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	0.00%
Line of Credit \| Base rate \| If Company elects to use alternative rates based on specified investment grade rating \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	0.65%
Line of Credit \| Federal funds rate
Debt Instrument [Line Items]
Basis spread on variable rate	0.50%
Line of Credit \| Eurodollar
Debt Instrument [Line Items]
Basis spread on variable rate	1.00%
Line of Credit \| Eurodollar \| Based on Company's Consolidated Leverage Ratio and type of loan \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	1.05%
Line of Credit \| Eurodollar \| Based on Company's Consolidated Leverage Ratio and type of loan \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	1.70%
Line of Credit \| Eurodollar \| If Company elects to use alternative rates based on specified investment grade rating \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	0.75%
Line of Credit \| Eurodollar \| If Company elects to use alternative rates based on specified investment grade rating \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	1.65%
Line of Credit \| Revolving Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 650,000,000
Term	4 years
Line of Credit \| Tranche 1 Term Loan Facility
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 480,000,000
Line of Credit \| Tranche 2 Term Loan Facility
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 220,000,000
Notes Payable
Debt Instrument [Line Items]
Notes payable to Trusts		4,167,149,000	$ 3,763,474,000
Notes payable subject to recourse		$ 2,601,960,000

Derivatives - Additional Information (Details) $ in Thousands	Dec. 31, 2018 USD ($) derivative
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Gain to be reclassified as a decrease to interest expense in 2019	$ 17,439
Number of derivative financial instruments \| derivative	28
Combined notional amount	$ 2,231,162
Derivatives with contingent features, net liability position	1,785
Derivatives with contingent features, contingent cash settlement value	$ 2,422

Derivatives - Schedule Summarizing Terms of Entity's Derivative Financial Instruments (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Derivative [Line Items]
Notional amounts	$ 2,231,162
Cash flow hedging \| Swap Agreements \| Minimum
Derivative [Line Items]
Notional amounts	$ 4,873
Strike rate	1.13%
Cash flow hedging \| Swap Agreements \| Maximum
Derivative [Line Items]
Notional amounts	$ 267,431
Strike rate	3.87%

Derivatives - Schedule of Balance Sheet Classification and Fair Value of Entity's Derivative Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Other assets
Derivative [Line Items]
Asset Derivatives	$ 42,324	$ 38,365
Other liabilities
Derivative [Line Items]
Liability Derivatives	$ 2,131	$ 9

Derivatives - Schedule of Information Relating to Gain (Loss) Recognized on Swap Agreements (Details) - Swap Agreements - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) recognized in OCI	$ 9,889	$ 8,499
Gain (loss) reclassified from OCI	$ 8,258	$ (8,853)	$ (18,800)

Notes Payable to Trusts - Additional Information (Details)		1 Months Ended			12 Months Ended			60 Months Ended	61 Months Ended
	Jul. 27, 2010 USD ($)	Jul. 31, 2005 USD ($) Security	May 31, 2005 USD ($) Security	Apr. 30, 2005 USD ($) Security	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jun. 30, 2010	Jul. 31, 2010	Jul. 11, 2011
Variable Interest Entity [Line Items]
Principal payments on notes payable to trusts					$ 88,662,000	$ 0	$ 0
Variable Interest Entity, Not Primary Beneficiary \| Trust III
Variable Interest Entity [Line Items]
Proceeds from issuance of securities		$ 41,238,000
Variable Interest Entity, Not Primary Beneficiary \| Trust III \| Preferred Securities
Variable Interest Entity [Line Items]
Issuance of securities		40,000,000
Variable Interest Entity, Not Primary Beneficiary \| Trust III \| Common Securities
Variable Interest Entity [Line Items]
Issuance of securities		$ 1,238,000
Number of securities issued (in securities) \| Security		1,238
Variable Interest Entity, Not Primary Beneficiary \| Trust II
Variable Interest Entity [Line Items]
Proceeds from issuance of securities			$ 42,269,000
Variable Interest Entity, Not Primary Beneficiary \| Trust II \| Preferred Securities
Variable Interest Entity [Line Items]
Issuance of securities			41,000,000
Variable Interest Entity, Not Primary Beneficiary \| Trust II \| Common Securities
Variable Interest Entity [Line Items]
Issuance of securities			$ 1,269,000
Number of securities issued (in securities) \| Security			1,269
Variable Interest Entity, Not Primary Beneficiary \| Trust
Variable Interest Entity [Line Items]
Proceeds from issuance of securities				$ 36,083,000
Variable Interest Entity, Not Primary Beneficiary \| Trust \| Preferred Securities
Variable Interest Entity [Line Items]
Issuance of securities				35,000,000
Variable Interest Entity, Not Primary Beneficiary \| Trust \| Common Securities
Variable Interest Entity [Line Items]
Issuance of securities				$ 1,083,000
Number of securities issued (in securities) \| Security				1,083
Operating Partnership \| Variable Interest Entity, Not Primary Beneficiary \| Trust III
Variable Interest Entity [Line Items]
Interest rate, fixed									6.91%
Interest rate swap, fixed interest rate										5.00%
Prepayment premium	$ 0
Operating Partnership \| Variable Interest Entity, Not Primary Beneficiary \| Trust III \| LIBOR
Variable Interest Entity [Line Items]
Basis spread on variable rate					2.40%
Operating Partnership \| Variable Interest Entity, Not Primary Beneficiary \| Trust II
Variable Interest Entity [Line Items]
Interest rate, fixed								6.70%
Interest rate swap, fixed interest rate					5.00%
Prepayment premium					$ 0
Operating Partnership \| Variable Interest Entity, Not Primary Beneficiary \| Trust II \| LIBOR
Variable Interest Entity [Line Items]
Basis spread on variable rate					2.40%
Operating Partnership \| Variable Interest Entity, Not Primary Beneficiary \| Trust
Variable Interest Entity [Line Items]
Interest rate swap, fixed interest rate					5.10%
Prepayment premium					$ 0
Operating Partnership \| Variable Interest Entity, Not Primary Beneficiary \| Trust \| LIBOR
Variable Interest Entity [Line Items]
Basis spread on variable rate					2.30%
Notes payable to Trusts \| Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Principal payments on notes payable to trusts					$ 88,662,000
Unamortized deferred financing costs, net					0	$ 2,146,000
Notes payable to Trusts \| Variable Interest Entity, Not Primary Beneficiary \| Trust
Variable Interest Entity [Line Items]
Notes payable to Trusts					$ 30,928,000

Notes Payable to Trusts - Schedule of Liabilities and Maximum Exposure to Loss Related to Trusts (Details) - Variable Interest Entity, Not Primary Beneficiary - Trust	Dec. 31, 2018 USD ($)
Variable Interest Entity [Line Items]
Investment Balance	$ 928,000
Maximum exposure to loss	30,000,000
Difference	0
Notes payable to Trusts
Variable Interest Entity [Line Items]
Notes payable to Trusts	$ 30,928,000

Exchangeable Senior Notes - Additional Information (Details)			1 Months Ended	12 Months Ended
	Dec. 31, 2018 USD ($)	Jun. 21, 2013 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2018 USD ($) day	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) shares
Debt Instrument [Line Items]
Cash paid for repurchase of debt				$ 1,109,854,000	$ 1,088,679,000	$ 1,122,442,000
Common Stock
Debt Instrument [Line Items]
Converted instrument, shares issued (in shares) \| shares						148,940
Converted instrument, amount						$ 13,066,000
2015 Notes
Debt Instrument [Line Items]
Principal amount of notes issued			$ 575,000,000
Fixed interest rate	3.125%		3.125%	3.125%
Related debt issuance costs			$ 11,992,000
Underwriting fee percentage			2.00%
Amortization period			5 years
Conversion ratio	0.01078
Redemption price as percentage of principal amount of notes plus accrued and unpaid interest			100.00%
Redemption price as percentage of principal amount of notes at request of debt holders and upon occurrence of designated event			100.00%
Variable Rate	4.00%			4.00%
2015 Notes \| Minimum
Debt Instrument [Line Items]
Number of days of written notice to holders of notes required for redemption			30 days
2015 Notes \| Maximum
Debt Instrument [Line Items]
Number of days of written notice to holders of notes required for redemption			60 days
2013 Notes
Debt Instrument [Line Items]
Principal amount of notes issued		$ 250,000,000
Fixed interest rate		2.375%
Related debt issuance costs	$ 10,000	$ 1,672,000		$ 10,000	35,000	43,000
Notes exchange, threshold percentage				130.00%
Notes exchange, threshold trading days \| day				20
Notes exchange, threshold consecutive trading days \| day				30
Debt, measurement input		1.50%
Unamortized cash discount	$ 230,000	$ 3,750,000		$ 230,000	184,000	788,000
Amortization period		5 years
Variable Rate	4.00%			4.00%
Principal amount repurchased	$ 49,259,000			$ 49,259,000	13,911,000	22,194,000
Cash paid for repurchase of debt				$ 80,270,000	$ 20,042,000	$ 35,261,000

Exchangeable Senior Notes - Carrying Amount of Equity Component and Principal Amount of Liability Component (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2015	Jun. 21, 2013
Debt Instrument [Line Items]
Principal amount of liability component	$ 562,374	$ 604,276
2015 Notes
Debt Instrument [Line Items]
Principal amount of liability component	575,000
Unamortized debt issuance costs				$ (11,992)
2013 Notes
Debt Instrument [Line Items]
Unamortized debt issuance costs	(10)	(35)	$ (43)		$ (1,672)
Senior Notes
Debt Instrument [Line Items]
Carrying amount of equity components	22,597	22,597
Unamortized debt issuance costs	(4,209)	(6,620)
Net carrying amount of liability components	562,374	604,276
Senior Notes \| 2015 Notes
Debt Instrument [Line Items]
Carrying amount of equity components	22,597	22,597
Principal amount of liability component	575,000	575,000
Unamortized discount - equity components	(8,417)	(12,974)
Senior Notes \| 2013 Notes
Debt Instrument [Line Items]
Carrying amount of equity components	0	0
Principal amount of liability component	0	49,259
Unamortized discount - equity components	0	(315)
Unamortized cash discount	$ 0	$ (74)

Exchangeable Senior Notes - Interest Cost Recognized (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
Contractual interest	$ 18,106	$ 19,303	$ 19,483
Amortization of discount	4,687	5,103	4,980
Total interest expense recognized	$ 22,793	$ 24,406	$ 24,463

Exchangeable Senior Notes - Repurchase of Debt (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jun. 21, 2013
Debt Instrument [Line Items]
Total consideration paid for repurchase	$ 1,109,854	$ 1,088,679	$ 1,122,442
2013 Notes
Debt Instrument [Line Items]
Principal amount repurchased	49,259	13,911	22,194
Extinguishment of liability component	49,019	13,692	21,363
Reacquisition of equity component	31,251	6,350	13,898
Total consideration paid for repurchase	80,270	20,042	35,261
Extinguishment of liability component	(49,019)	(13,692)	(21,363)
Discount on exchangeable senior notes	(230)	(184)	(788)	$ (3,750)
Related debt issuance costs	(10)	(35)	(43)	$ (1,672)
Gain/(loss) on repurchase	$ 0	$ 0	$ 0

Related Party and Affiliated Real Estate Joint Venture Transactions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Management fees and other income	$ 41,757	$ 39,379	$ 39,842
Affiliated entities and joint ventures
Related Party Transaction [Line Items]
Management fees and other income	$ 14,123	$ 12,650	$ 16,066

Stockholders' Equity (Details) $ / shares in Units, $ in Thousands			1 Months Ended	4 Months Ended	12 Months Ended
	May 06, 2016 USD ($) sales_agent	Aug. 28, 2015 USD ($) sales_agent	Jul. 31, 2016 USD ($) $ / shares shares	May 06, 2016 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) item $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($)
Changes In Equity And Comprehensive Income Line Items [Line Items]
Common stock, shares authorized (in shares)					500,000,000	500,000,000
Common stock, par value (in dollars per share) \| $ / shares					$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)					50,000,000	50,000,000
Preferred stock, par value (in dollars per share) \| $ / shares					$ 0.01	$ 0.01
Common stock, shares issued (in shares)					127,103,750	126,007,091
Common stock, shares outstanding (in shares)					127,103,750	126,007,091
Preferred stock, shares issued (in shares)					0	0
Preferred stock, shares outstanding (in shares)					0	0
Number of votes, common stockholder rights \| item					1
Net proceeds from sale of stock \| $					$ 90,231	$ 0	$ 123,424
“At the market” equity program
Changes In Equity And Comprehensive Income Line Items [Line Items]
Aggregate offering price \| $	$ 400,000	$ 400,000
Number of sales agents \| sales_agent	5	5
Common stock sold (in shares)			550,000	831,300	933,789
Average sales price (in dollars per share) \| $ / shares			$ 92.04	$ 89.66
Net proceeds from sale of stock \| $			$ 50,062	$ 73,360
Available for issuance \| $					$ 257,929

Noncontrolling Interest Represented By Preferred Operating Partnership Units (Details) - USD ($) $ / shares in Units, $ in Thousands				1 Months Ended			3 Months Ended								12 Months Ended
	Dec. 01, 2018	Apr. 18, 2017	Jun. 25, 2007	Dec. 31, 2014	Oct. 31, 2014	Jun. 30, 2007	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Noncontrolling Interest [Line Items]
Loan to holders of preferred OP units							$ 108,644				$ 120,230				$ 108,644	$ 120,230
Number of units issued (in shares)							0	0	21,768	0	64,708	25,520	272,400	0	21,768	362,628
Value of units issued							$ 0	$ 0	$ 1,877	$ 0	$ 5,618	$ 2,000	$ 6,810	$ 0	$ 1,877	$ 14,428
Series A Units
Noncontrolling Interest [Line Items]
Fixed priority return on preferred OP units, amount					$ 101,700
Fixed priority return on preferred OP units, stated return rate		2.30%				5.00%
Fixed priority return on preferred OP units, liquidation value						$ 115,000
Preferred units outstanding (in shares)							875,480								875,480
Series A Units \| Holders Of Series A Preferred Operating Partnership Units
Noncontrolling Interest [Line Items]
Loan to holders of preferred OP units			$ 100,000				$ 100,000								$ 100,000
Maximum number of preferred OP units converted prior to the maturity date of the loan (in shares)					114,500
Note receivable interest rate		2.10%	4.90%
Additional units redeemed			0
Series B Units
Noncontrolling Interest [Line Items]
Preferred units outstanding (in shares)							1,676,087								1,676,087
Liquidation value (in dollars per share)							$ 25								$ 25
Fixed liquidation value							$ 41,902								$ 41,902
Annual rate of return percent															6.00%
Series C Units
Noncontrolling Interest [Line Items]
Loan to holders of preferred OP units							$ 19,735				$ 20,230				$ 19,735	20,230
Preferred units outstanding (in shares)							296,020								296,020
Note receivable interest rate				5.00%
Liquidation value (in dollars per share)							$ 42.1								$ 42.1
Fixed liquidation value							$ 12,462								$ 12,462
Quarterly distribution per preferred OP unit payable above quarterly distribution for common OP Unit (in dollars per share)															$ 0.18
Basis for determining fixed quarterly distribution in year 5, period before fifth anniversary															12 months
Period from date of issuance after which preferred OP units will become redeemable at the option of the holder															1 year
Period from date of issuance after which preferred OP units will become convertible into common OP units at the option of the holder															1 year
Preferred OP units conversion ratio (in units)															0.9145
Conversion of units, units converted (in shares)	407,996
Series D Units
Noncontrolling Interest [Line Items]
Preferred units outstanding (in shares)							3,682,521								3,682,521
Liquidation value (in dollars per share)							$ 25								$ 25
Fixed liquidation value							$ 92,064								$ 92,064
Value of units issued																$ 11,161	$ 67,193
Series D Units \| Minimum
Noncontrolling Interest [Line Items]
Annual rate of return percent															3.00%
Series D Units \| Maximum
Noncontrolling Interest [Line Items]
Annual rate of return percent															5.00%
Series D Units \| Operating Partnership
Noncontrolling Interest [Line Items]
Number of units issued (in shares)																446,420	2,687,711
Preferred Operating Partnership, Series C
Noncontrolling Interest [Line Items]
Reduction of noncontrolling interest for note receivable							8,644								$ 8,644
Operating Partnership
Noncontrolling Interest [Line Items]
Conversion of units, units issued upon conversion (in shares)	373,113
Reduction of noncontrolling interest for note receivable							$ 11,091								$ 11,091

Noncontrolling Interests In Operating Partnership and Other Noncontrolling Interests - Additional Information (Details) $ / shares in Units, $ in Thousands		12 Months Ended
	Dec. 01, 2018 shares	Dec. 31, 2018 USD ($) store joint_venture $ / shares shares	Dec. 31, 2017 store	Dec. 31, 2016 store
Noncontrolling Interest [Line Items]
Period used as a denomination to determine the average closing price of common stock		10 days
Ten day average closing stock price (in dollars per share) \| $ / shares		$ 91.64
OP units outstanding (in units)		5,994,251
Consideration to be paid on redemption of common OP units \| $		$ 549,313
Number of owned stores \| store		28	39	8
Operating Partnership
Noncontrolling Interest [Line Items]
Ownership interest held by entity (as a percent)		91.00%
Voting interests of third-party owners		9.00%
Operating Partnership
Noncontrolling Interest [Line Items]
Conversion of units, units issued upon conversion (in shares)	373,113
Reduction of noncontrolling interest for note receivable \| $		$ 11,091
Common Stock
Noncontrolling Interest [Line Items]
Unit conversion ratio		1
Other
Noncontrolling Interest [Line Items]
Number of consolidated joint ventures \| joint_venture		2
Series C Units
Noncontrolling Interest [Line Items]
Conversion of units, units converted (in shares)	407,996
Joint venture one
Noncontrolling Interest [Line Items]
Number of owned stores \| store		2
Minimum \| Other
Noncontrolling Interest [Line Items]
Voting interests of third-party owners		5.00%
Maximum \| Other
Noncontrolling Interest [Line Items]
Voting interests of third-party owners		20.00%

Noncontrolling Interests In Operating Partnership and Other Noncontrolling Interests - Schedule of OP Unit Activity (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Noncontrolling Interest [Abstract]
OP Units redeemed for common stock (in shares)	35,000	0	23,850
OP Units redeemed for cash (in shares)	30,000	33,896	6,760
Cash paid for OP Units redeemed	$ 2,558	$ 2,510	$ 506
OP Units issued in conjunction with acquisitions (in shares)	21,768	90,228	93,569
Value of OP Units issued in conjunction with acquisitions	$ 1,877	$ 7,618	$ 7,247

Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for issuance under plans (in shares)	1,587,625
Weighted average fair value of stock options granted (in dollars per share)			$ 20.30
Options granted (in shares)	0	0	35,800
Weighted average forfeiture rate	7.40%
Net proceeds from exercise of stock options	$ 1,169	$ 1,266	$ 1,444
Dividend yield			3.60%
Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
Expiration period	10 years
Compensation cost	$ 570	649	$ 729
Net proceeds from exercise of stock options	1,169	1,266	1,444
Unrecognized compensation cost	$ 344
Term over which unrecognized compensation cost recognized	8 months 21 days
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
Weighted average forfeiture rate	10.20%
Compensation cost	$ 10,606	8,072	$ 7,316
Unrecognized compensation cost	$ 10,870
Term over which unrecognized compensation cost recognized	2 years
Performance-Based Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Compensation cost	$ 1,873	840
Unrecognized compensation cost	$ 2,739	$ 1,681
Term over which unrecognized compensation cost recognized	2 years	2 years
Performance component weight percentage	50.00%
Minimum shares issued for each PSU (in shares)	0
Maximum shares issued for each PSU (in shares)	2
Dividend yield	0.00%	0.00%

Stock-Based Compensation - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stock option activity
Balance at the beginning of the period (in shares)	472,156	510,574	572,629
Granted (in shares)	0	0	35,800
Exercised (in shares)	(54,575)	(38,418)	(97,855)
Balance at the end of the period (in shares)	417,581	472,156	510,574
Vested and Expected to Vest (in shares)	416,567
Exercisable at the end of the period (in shares)	377,292
Weighted average exercise price
Balance at the beginning of the period (in dollars per share)	$ 30.41	$ 30.60	$ 24.42
Granted (in dollars per share)			85.99
Exercised (in dollars per share)	21.45	32.94	14.75
Balance at the end of the period (in dollars per share)	31.58	$ 30.41	$ 30.60
Vested and Expected to Vest (in dollars per share)	31.46
Exercisable at the end of the period (in dollars per share)	$ 26.72
Weighted average remaining contractual life
Outstanding at the beginning of period	2 years 284 days
Vested and Expected to Vest	2 years 281 days
Exercisable at the end of period	2 years 128 days
Aggregate intrinsic value
Outstanding at the end of the period	$ 24,597
Vested and Expected to Vest at the end of the period	24,587
Exercisable at the end of the period	$ 24,057

Stock-Based Compensation - Assumptions Used to Estimate Fair Value of Stock Options (Details)	12 Months Ended
	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Expected volatility	37.00%
Dividend yield	3.60%
Risk-free interest rate	1.30%
Average expected term	5 years

Stock-Based Compensation - Summary Stock Options Outstanding and Exercisable (Details)	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding (in shares) \| shares	417,581
Options outstanding, weighted average remaining contractual life	2 years 285 days
Weighted average exercise price (in dollars per share)	$ 31.58
Options exercisable (in shares) \| shares	377,292
Options exercisable, weighted average exercise price (in dollars per share)	$ 26.72
$6.22 - $6.22
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit (in dollars per share)	6.22
Exercise price range, upper limit (in dollars per share)	$ 6.22
Options outstanding (in shares) \| shares	139,250
Options outstanding, weighted average remaining contractual life	47 days
Weighted average exercise price (in dollars per share)	$ 6.22
Options exercisable (in shares) \| shares	139,250
Options exercisable, weighted average exercise price (in dollars per share)	$ 6.22
$11.59 - $11.59
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit (in dollars per share)	11.59
Exercise price range, upper limit (in dollars per share)	$ 11.59
Options outstanding (in shares) \| shares	20,080
Options outstanding, weighted average remaining contractual life	1 year 47 days
Weighted average exercise price (in dollars per share)	$ 11.59
Options exercisable (in shares) \| shares	20,080
Options exercisable, weighted average exercise price (in dollars per share)	$ 11.59
$12.21 - $12.21
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit (in dollars per share)	12.21
Exercise price range, upper limit (in dollars per share)	$ 12.21
Options outstanding (in shares) \| shares	77,400
Options outstanding, weighted average remaining contractual life	1 year 66 days
Weighted average exercise price (in dollars per share)	$ 12.21
Options exercisable (in shares) \| shares	77,400
Options exercisable, weighted average exercise price (in dollars per share)	$ 12.21
$19.6 - $28.79
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit (in dollars per share)	19.60
Exercise price range, upper limit (in dollars per share)	$ 28.79
Options outstanding (in shares) \| shares	29,469
Options outstanding, weighted average remaining contractual life	2 years 237 days
Weighted average exercise price (in dollars per share)	$ 23.56
Options exercisable (in shares) \| shares	29,469
Options exercisable, weighted average exercise price (in dollars per share)	$ 23.56
$38.4 - $38.4
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit (in dollars per share)	38.4
Exercise price range, upper limit (in dollars per share)	$ 38.4
Options outstanding (in shares) \| shares	10,360
Options outstanding, weighted average remaining contractual life	4 years 51 days
Weighted average exercise price (in dollars per share)	$ 38.4
Options exercisable (in shares) \| shares	10,360
Options exercisable, weighted average exercise price (in dollars per share)	$ 38.40
$47.5 - $47.5
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit (in dollars per share)	47.5
Exercise price range, upper limit (in dollars per share)	$ 47.5
Options outstanding (in shares) \| shares	17,687
Options outstanding, weighted average remaining contractual life	5 years 47 days
Weighted average exercise price (in dollars per share)	$ 47.5
Options exercisable (in shares) \| shares	17,687
Options exercisable, weighted average exercise price (in dollars per share)	$ 47.50
$65.36 - $65.36
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit (in dollars per share)	65.36
Exercise price range, upper limit (in dollars per share)	$ 65.36
Options outstanding (in shares) \| shares	20,395
Options outstanding, weighted average remaining contractual life	6 years 55 days
Weighted average exercise price (in dollars per share)	$ 65.36
Options exercisable (in shares) \| shares	15,297
Options exercisable, weighted average exercise price (in dollars per share)	$ 65.36
$65.45 - $65.45
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit (in dollars per share)	65.45
Exercise price range, upper limit (in dollars per share)	$ 65.45
Options outstanding (in shares) \| shares	17,140
Options outstanding, weighted average remaining contractual life	6 years 47 days
Weighted average exercise price (in dollars per share)	$ 65.45
Options exercisable (in shares) \| shares	12,345
Options exercisable, weighted average exercise price (in dollars per share)	$ 65.45
$73.52 - $73.52
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit (in dollars per share)	73.52
Exercise price range, upper limit (in dollars per share)	$ 73.52
Options outstanding (in shares) \| shares	50,000
Options outstanding, weighted average remaining contractual life	6 years 212 days
Weighted average exercise price (in dollars per share)	$ 73.52
Options exercisable (in shares) \| shares	37,500
Options exercisable, weighted average exercise price (in dollars per share)	$ 73.52
$85.99 - $85.99
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit (in dollars per share)	85.99
Exercise price range, upper limit (in dollars per share)	$ 85.99
Options outstanding (in shares) \| shares	35,800
Options outstanding, weighted average remaining contractual life	7 years 55 days
Weighted average exercise price (in dollars per share)	$ 85.99
Options exercisable (in shares) \| shares	17,904
Options exercisable, weighted average exercise price (in dollars per share)	$ 85.99

Stock-Based Compensation - Summary of Employee and Director Share Grant Activity (Details) - Restricted Stock - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restricted Stock Grants
Balance at the beginning of the period (in shares)	266,475	299,585	318,409
Granted (in shares)	85,066	95,392	119,931
Released (in shares)	(116,656)	(120,323)	(128,808)
Cancelled (in shares)	(11,771)	(8,179)	(9,947)
Balance at the end of the period (in shares)	223,114	266,475	299,585
Weighted-Average Grant-Date Fair
Balance at the beginning of the period (in dollars per share)	$ 74.76	$ 70.57	$ 55.75
Granted (in dollars per share)	86.14	74.49	87.61
Released (in dollars per share)	72.38	63.95	50.05
Cancelled (in dollars per share)	80.96	77.25	67.36
Balance at the end of the period (in dollars per share)	$ 80.02	$ 74.76	$ 70.57

Stock-Based Compensation - Summary of PSU Activity (Details) - Performance-Based Stock Units - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Units
Balance at the beginning of the period (in shares)	30,071	0
Granted (in shares)	28,735	30,071
Balance at the end of the period (in shares)	58,806	30,071
Weighted-Average Grant-Date Fair Value
Balance at the beginning of the period (in dollars per share)	$ 83.84	$ 0.00
Granted (in dollars per share)	96.19	83.84
Balance at the end of the period (in dollars per share)	$ 89.87	$ 83.84

Stock-Based Compensation - Assumptions Used to Calculate Fair Value of Awards (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free rate			1.30%
Volatility			37.00%
Expected term			5 years
Dividend yield			3.60%
Performance-Based Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value	$ 5,321	$ 2,630
Compensation cost	$ 1,873	$ 840
Risk-free rate	2.37%	1.62%
Volatility	22.60%	21.40%
Expected term	2 years 10 months 30 days	2 years 10 months 1 day
Dividend yield	0.00%	0.00%
Unrecognized compensation cost	$ 2,739	$ 1,681
Term over which unrecognized compensation cost recognized	2 years	2 years

Employee Benefit Plan - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Retirement Benefits [Abstract]
Employee contribution to retirement saving plan as a percentage of annual salary, maximum	60.00%
Matching contributions made by the entity during the period	$ 2,833	$ 2,212	$ 1,944
Percentage of company's matching contributions of first 3 percent of employee's compensation	100.00%
Percentage of employee's compensation that qualifies for 100 percent matching contribution by the company	3.00%
Maximum percentage of the company's matching contributions of next 2 percent of employee's compensation	50.00%
Percentage of employee's compensation that qualifies for 50 percent matching contribution by the company	2.00%

Income Taxes - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2018 subsidiary
Income Tax [Line Items]
Tax benefit related to remeasurment of deferred tax balance and valuation allowance \| $	$ 8,606
Extra Space Management, Inc
Income Tax [Line Items]
Number of taxable REIT subsidiaries \| subsidiary		1

Income Taxes - Income Tax Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Federal
Current expense, federal	$ 9,136	$ 5,677	$ 14,627
Tax credits/true-up, federal	(5,841)	(5,573)	(312)
Change in deferred expense/(benefit), federal	3,730	1,700	(369)
Income tax expense, federal	7,025	1,804	13,946
State
Current expense, state	2,426	1,662	2,368
Tax credits/true-up, state	(175)	(383)	0
Change in deferred expense/(benefit), state	(32)	542	(467)
Income tax expense, state	2,219	1,821	1,901
Current expense, total	11,562	7,339	16,995
Tax credits/true-up, total	(6,016)	(5,956)	(312)
Change in deferred expense/(benefit), total	3,698	2,242	(836)
Total provision	$ 9,244	$ 3,625	$ 15,847

Income Taxes - Reconciliation of Statutory Income Tax Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Expected tax at statutory rate	$ 95,828	$ 186,274	$ 144,708
Non-taxable REIT income	(83,022)	(170,811)	(131,112)
State and local tax expense - net of federal benefit	2,385	2,306	2,399
Change in valuation allowance	(1,052)	159	(845)
Tax credits/true-up	(6,016)	(5,956)	(312)
Remeasurement of deferred balances	0	(8,460)	0
Miscellaneous	1,121	113	1,009
Total provision	$ 9,244	$ 3,625	$ 15,847
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Expected tax at statutory rate	21.00%	35.00%	35.00%
Non-taxable REIT income	(18.20%)	(32.10%)	(31.70%)
State and local tax expense - net of federal benefit	0.50%	0.40%	0.60%
Change in valuation allowance	(0.20%)	0.00%	(0.20%)
Tax credits/true-up	(1.30%)	(1.10%)	(0.10%)
Remeasurement of deferred balances	0.00%	(1.60%)	0.00%
Miscellaneous	0.20%	0.00%	0.20%
Total provision	2.00%	0.60%	3.80%

Income Taxes - Sources of Temporary Differences (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred Tax Liabilities, Gross [Abstract]
Fixed assets	$ (20,907)	$ (15,271)
Other	(96)	(108)
State deferred taxes	(3,076)	(2,822)
Total deferred tax liabilities	(24,079)	(18,201)
Deferred Tax Assets, Gross [Abstract]
Captive insurance subsidiary	324	252
Accrued liabilities	1,772	873
Stock compensation	1,604	1,287
Solar credit	0	43
Other	53	57
SmartStop TRS	219	219
State deferred taxes	7,196	7,802
Total deferred tax assets	11,168	10,533
Valuation allowance	(3,872)	(4,924)
Net deferred income tax liabilities	$ (16,783)	$ (12,592)

Segment Information - Additional Information (Details) - segment	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2016
Segment Reporting [Abstract]
Number of reportable segments	2	3

Segment Information - Schedule of Financial Information of Business Segments (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Revenues	$ 307,353	$ 306,953	$ 296,813	$ 285,485	$ 281,842	$ 284,156	$ 276,003	$ 263,008	$ 1,196,604	$ 1,105,009	$ 991,875
Operating expenses	150,676	153,362	152,097	151,573	140,728	144,275	139,596	138,805	607,708	563,404	542,037
Net operating income	156,677	153,591	144,716	133,912	141,114	139,881	136,407	124,203	619,703	654,394	458,303
Property management fees and other income									41,757	39,379	39,842
General and administrative expense									(81,256)	(78,961)	(81,806)
Gain on real estate transactions, earnout from prior acquisitions and impairment of real estate									30,807	112,789	8,465
Interest expense									(178,436)	(153,511)	(133,479)
Non-cash interest expense related to amortization of discount on equity component of exchangeable senior notes									(4,687)	(5,103)	(4,980)
Interest income									5,292	6,736	10,998
Equity in earnings of unconsolidated real estate ventures									14,452	15,331	12,895
Equity in earnings of unconsolidated real estate ventures - gain on sale of real estate assets and purchase of partners' interests									0	0	69,199
Income tax expense									(9,244)	(3,625)	(15,847)
Net income	$ 109,250	$ 139,687	$ 102,713	$ 95,430	$ 229,315	$ 101,075	$ 94,098	$ 89,734	447,080	514,222	397,089
Operating Segments
Segment Reporting Information [Line Items]
Revenues									1,154,847	1,065,630	952,033
Operating expenses									317,402	291,147	265,560
Net operating income									837,445	774,483	686,473
Operating Segments \| Self-Storage Operations
Segment Reporting Information [Line Items]
Revenues									1,039,340	967,229	864,742
Operating expenses									291,695	271,974	250,005
Net operating income									747,645	695,255	614,737
Operating Segments \| Tenant Reinsurance
Segment Reporting Information [Line Items]
Revenues									115,507	98,401	87,291
Operating expenses									25,707	19,173	15,555
Net operating income									89,800	79,228	71,736
Segment reconciling items
Segment Reporting Information [Line Items]
Property management fees and other income									41,757	39,379	39,842
General and administrative expense									(81,256)	(78,961)	(81,806)
Depreciation and amortization expense									(209,050)	(193,296)	(182,560)
Acquisition and other related costs									0	0	(12,111)
Gain on real estate transactions, earnout from prior acquisitions and impairment of real estate									30,807	112,789	8,465
Interest expense									(178,436)	(153,511)	(133,479)
Non-cash interest expense related to amortization of discount on equity component of exchangeable senior notes									(4,687)	(5,103)	(4,980)
Interest income									5,292	6,736	10,998
Equity in earnings of unconsolidated real estate ventures									14,452	15,331	12,895
Equity in earnings of unconsolidated real estate ventures - gain on sale of real estate assets and purchase of partners' interests									0	0	69,199
Income tax expense									$ (9,244)	$ (3,625)	$ (15,847)

Commitments and Contingencies - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) store Facility	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Other Commitments [Line Items]
Number of owned stores that have leases \| Facility	23
Expense related to ground leases \| $	$ 8,229	$ 6,898	$ 4,578
Commitment to acquire stores
Other Commitments [Line Items]
Number of properties to be acquired	18
Other commitment \| $	$ 271,526
Commitment to acquire stores, 2019
Other Commitments [Line Items]
Other commitment \| $	$ 247,498
Number of store acquisitions expected to close	16
Commitment to acquire stores, 2020
Other Commitments [Line Items]
Other commitment \| $	$ 24,028
Number of store acquisitions expected to close	2
Commitment to acquire stores with joint venture partners
Other Commitments [Line Items]
Number of properties to be acquired	13
Other commitment \| $	$ 73,860
Commitment to acquire stores with joint venture partners, 2019
Other Commitments [Line Items]
Number of store acquisitions expected to close	11
Commitment to acquire stores with joint venture partners, 2020
Other Commitments [Line Items]
Number of store acquisitions expected to close	2

Commitments and Contingencies - Schedule of Future Minimum Payments (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Less than 1 year	$ 8,203
Year 2	8,307
Year 3	8,137
Year 4	7,837
Year 5	7,021
Thereafter	111,653
Total	$ 151,158

Supplementary Quarterly Financial Data (Unaudited) - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 307,353	$ 306,953	$ 296,813	$ 285,485	$ 281,842	$ 284,156	$ 276,003	$ 263,008	$ 1,196,604	$ 1,105,009	$ 991,875
Cost of operations	150,676	153,362	152,097	151,573	140,728	144,275	139,596	138,805	607,708	563,404	542,037
Income from operations	156,677	153,591	144,716	133,912	141,114	139,881	136,407	124,203	619,703	654,394	458,303
Net income	109,250	139,687	102,713	95,430	229,315	101,075	94,098	89,734	447,080	514,222	397,089
Net income attributable to common stockholders	$ 101,462	$ 130,418	$ 95,153	$ 88,256	$ 215,983	$ 93,742	$ 87,006	$ 82,282	$ 415,289	$ 479,013	$ 366,127
Earnings per common share-basic (in dollars per share)	$ 0.80	$ 1.03	$ 0.75	$ 0.70	$ 1.71	$ 0.74	$ 0.69	$ 0.65	$ 3.29	$ 3.79	$ 2.92
Earnings per common share-diluted (in dollars per share)	$ 0.80	$ 1.02	$ 0.75	$ 0.70	$ 1.69	$ 0.74	$ 0.69	$ 0.64	$ 3.27	$ 3.76	$ 2.91

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

- Definition

The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

+ References

+ Details

Subsequent Events - Additional Information (Details) $ in Thousands	2 Months Ended	3 Months Ended								12 Months Ended
	Feb. 26, 2019 USD ($) store	Dec. 31, 2018 USD ($) store	Sep. 30, 2018 USD ($) store	Jun. 30, 2018 USD ($) store	Mar. 31, 2018 USD ($) store	Dec. 31, 2017 USD ($) store	Sep. 30, 2017 USD ($) store	Jun. 30, 2017 USD ($) store	Mar. 31, 2017 USD ($) store	Dec. 31, 2018 USD ($) store	Dec. 31, 2017 USD ($) store
Subsequent Event [Line Items]
Number of stores acquired \| store		6	6	17	5	37	4	3	2	34	46
Cash paid to acquire properties		$ 74,868	$ 71,989	$ 148,650	$ 70,171	$ 502,845	$ 29,919	$ 16,608	$ 25,541	$ 365,678	$ 574,913
Loan assumed		$ 0	$ 0	$ 87,500	$ 0	$ 14,592	$ 0	$ 9,463	$ 0	$ 87,500	$ 24,055
Subsequent Event \| Extra Space West One LLC and Extra Space Two LLC
Subsequent Event [Line Items]
Number of stores acquired \| store	12
Cash paid to acquire properties	$ 172,515
Loan assumed	$ 17,157

Schedule III - Real Estate and Accumulated Depreciation - Activity in Real Estate Facilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Real estate, gross:
Balance at end of year	$ 8,754,269
Accumulated depreciation:
Balance at beginning of year	1,060,060
Balance at end of year	1,262,438	$ 1,060,060
Net real estate assets:
Net real estate assets	7,491,831	7,132,431	$ 6,770,447
Aggregate cost of real estate for U.S. federal income tax purposes	7,306,350
Operating facilities
Real estate, gross:
Balance at beginning of year	8,158,741	7,649,448	6,392,487
Acquisitions	459,223	628,391	1,159,304
Improvements	64,336	71,090	92,480
Transfers from construction in progress (to operating facilities)	49,449	19,079	26,400
Dispositions and other	(22,434)	(209,267)	(21,223)
Balance at end of year	8,709,315	8,158,741	7,649,448
Accumulated depreciation:
Balance at beginning of year	1,060,060	900,861	728,087
Depreciation expense	203,030	185,903	174,906
Dispositions and other	(652)	(26,704)	(2,132)
Balance at end of year	1,262,438	1,060,060	900,861
Real estate under development/redevelopment
Real estate, gross:
Balance at beginning of year	33,750	21,860	24,909
Current development	60,677	33,484	23,404
Transfers from construction in progress (to operating facilities)	(49,449)	(19,079)	(26,400)
Dispositions and other	(24)	(2,515)	(53)
Balance at end of year	$ 44,954	$ 33,750	$ 21,860