Extra Space Storage (EXR) 10-Q 6 May 16 2016 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2016	Apr. 30, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q1
Trading Symbol	EXR
Entity Registrant Name	Extra Space Storage Inc.
Entity Central Index Key	1,289,490
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		125,207,702

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Assets:
Real estate assets, net	$ 5,933,959	$ 5,689,309
Investments in unconsolidated real estate ventures	89,224	103,007
Cash and cash equivalents	49,753	75,799
Restricted cash	32,003	30,738
Receivables from related parties and affiliated real estate joint ventures	15,739	2,205
Other assets, net	170,741	170,349
Total assets	6,291,419	6,071,407
Liabilities, Noncontrolling Interests and Equity:
Notes payable, net	2,842,076	2,758,567
Exchangeable senior notes, net	606,887	623,863
Notes payable to trusts, net	117,225	117,191
Lines of credit	116,000	36,000
Accounts payable and accrued expenses	77,108	82,693
Other liabilities	106,738	80,489
Total liabilities	$ 3,866,034	$ 3,698,803
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
Common stock, $0.01 par value, 500,000,000 shares authorized, 125,129,324 and 124,119,531 shares issued and outstanding at March 31, 2016 and December 31, 2015, respectively	$ 1,251	$ 1,241
Additional paid-in capital	2,506,551	2,431,754
Accumulated other comprehensive loss	(35,939)	(6,352)
Accumulated deficit	(328,801)	(337,566)
Total Extra Space Storage Inc. stockholders' equity	2,143,062	2,089,077
Noncontrolling interest represented by Preferred Operating Partnership units, net of $120,230 notes receivable	80,371	80,531
Noncontrolling interests in Operating Partnership	201,791	202,834
Other noncontrolling interests	161	162
Total noncontrolling interests and equity	2,425,385	2,372,604
Total liabilities, noncontrolling interests and equity	$ 6,291,419	$ 6,071,407

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	50,000,000	50,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	125,129,324	124,119,531
Common stock, shares outstanding	125,129,324	124,119,531
Note receivable from noncontrolling interest represented by Preferred Operating Partnership units	$ 120,230	$ 120,230

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Revenues:
Property rental	$ 199,488	$ 148,894
Tenant reinsurance	20,555	16,510
Management fees and other income	9,360	7,750
Total revenues	229,403	173,154
Expenses:
Property operations	61,112	47,244
Tenant reinsurance	4,311	2,928
Acquisition related costs	4,053	869
General and administrative	23,402	16,249
Depreciation and amortization	42,897	30,428
Total expenses	135,775	97,718
Income from operations	93,628	75,436
Loss on earnout from prior acquisition	(1,544)
Interest expense	(31,359)	(21,431)
Non-cash interest expense related to amortization of discount on equity component of exchangeable senior notes	(1,233)	(697)
Interest income	1,714	856
Interest income on note receivable from Preferred Operating Partnership unit holder	1,213	1,213
Income before equity in earnings of unconsolidated real estate ventures and income tax expense	62,419	55,377
Equity in earnings of unconsolidated real estate ventures	2,830	2,650
Equity in earnings of unconsolidated real estate ventures - gain on sale of real estate assets and purchase of joint venture partners' interests	26,923	2,857
Income tax expense	(2,765)	(2,248)
Net income	89,407	58,636
Net income allocated to Preferred Operating Partnership noncontrolling interests	(3,180)	(2,926)
Net income allocated to Operating Partnership and other noncontrolling interests	(3,635)	(1,968)
Net income attributable to common stockholders	$ 82,592	$ 53,742
Earnings per common share
Basic	$ 0.66	$ 0.46
Diluted	$ 0.66	$ 0.46
Weighted average number of shares
Basic	124,754,174	116,117,615
Diluted	131,956,094	122,595,718
Cash dividends paid per common share	$ 0.59	$ 0.47

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 89,407	$ 58,636
Other comprehensive income (loss):
Change in fair value of interest rate swaps	(31,148)	(6,593)
Total comprehensive income	58,259	52,043
Less: comprehensive income attributable to noncontrolling interests	5,254	4,617
Comprehensive income attributable to common stockholders	$ 53,005	$ 47,426

Condensed Consolidated Stateme6

Condensed Consolidated Statement of Noncontrolling Interests and Equity - 3 months ended Mar. 31, 2016 - USD ($) $ in Thousands	Total	Series A Preferred Operating Partnership [Member]	Series B Preferred Operating Partnership [Member]	Series C Preferred Operating Partnership [Member]	Series D Preferred Operating Partnership [Member]	Common Operating Partnership [Member]	Other [Member]	Par Value [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]
Balances 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)
Balances (in shares) at Dec. 31, 2015	124,119,531							124,119,531
Issuance of common stock upon the exercise of options	$ 13								13
Issuance of common stock upon the exercise of options (in shares)								850
Restricted stock grants issued (in shares)								47,768
Restricted stock grants cancelled (in shares)								(1,354)
Issuance of common stock, net of offering costs	73,574							$ 8	73,566
Issuance of common stock, net of offering costs (in shares)								831,300
Compensation expense related to stock-based awards	1,710								1,710
Redemption of Operating Partnership units for common stock						(12)			12
Redemption of Operating Partnership units for common stock (in shares)								320
Repurchase of equity portion of 2013 exchangeable senior notes	(774)							$ 2	(776)
Repurchase of equity portion of 2013 exchangeable senior notes (in shares)								130,909
Net income	89,407	1,838	629	542	171	3,636	(1)				82,592
Other comprehensive income loss	(31,148)	(210)				(1,351)				(29,587)
Tax effect from vesting of restricted stock grants and stock option exercises	272								272
Distributions to Operating Partnership units held by noncontrolling interests	(6,446)	(1,788)	(629)	(542)	(171)	(3,316)
Dividends paid on common stock at $0.59 per share	(73,827)										(73,827)
Balances at Mar. 31, 2016	$ 2,425,385	$ 14,029	$ 41,902	$ 10,730	$ 13,710	$ 201,791	$ 161	$ 1,251	$ 2,506,551	$ (35,939)	$ (328,801)
Balances (in shares) at Mar. 31, 2016	125,129,324							125,129,324

Condensed Consolidated Stateme7

Condensed Consolidated Statement of Noncontrolling Interests and Equity (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Stockholders' Equity [Abstract]
Dividends paid on common stock, per share	$ 0.59	$ 0.47

Condensed Consolidated Stateme8

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash flows from operating activities:
Net income	$ 89,407	$ 58,636
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	42,897	30,428
Amortization of deferred financing costs	2,823	1,598
Non-cash interest expense related to amortization of discount on equity component of exchangeable senior notes	1,233	697
Non-cash interest expense related to amortization of premium on notes payable	(354)	(747)
Compensation expense related to stock-based awards	1,710	1,142
Gain on sale of real estate assets and purchase of joint venture partners' interests	(26,923)	(2,857)
Loss on real estate transactions and earnout from prior acquisition	(1,544)
Distributions from unconsolidated real estate ventures in excess of earnings	998	2,601
Changes in operating assets and liabilities:
Receivables from related parties and affiliated real estate joint ventures	(2,878)	(2,367)
Other assets	(5,276)	(2,637)
Accounts payable and accrued expenses	(5,642)	6,032
Other liabilities	(985)	(5,087)
Net cash provided by operating activities	95,466	87,439
Cash flows from investing activities:
Acquisition of real estate assets	(234,820)	(77,082)
Development and redevelopment of real estate assets	(6,543)	(3,140)
Change in restricted cash	(1,265)	(10,105)
Investment in unconsolidated real estate ventures	(4,794)
Return of investment in unconsolidated real estate ventures	318
Purchase/issuance of notes receivable	(10,656)
Purchase of equipment and fixtures	(908)	(1,184)
Net cash used in investing activities	(258,668)	(91,511)
Cash flows from financing activities:
Proceeds from the sale of common stock, net of offering costs	73,574
Repurchase of exchangeable senior notes	(19,639)
Proceeds from notes payable and lines of credit	195,976	290,768
Principal payments on notes payable and lines of credit	(32,859)	(228,878)
Deferred financing costs	(1,286)	(1,419)
Net proceeds from exercise of stock options	13	970
Proceeds from termination of interest rate cap	1,650
Dividends paid on common stock	(73,827)	(54,732)
Distributions to noncontrolling interests	(6,446)	(4,996)
Net cash provided by financing activities	137,156	1,713
Net decrease in cash and cash equivalents	(26,046)	(2,359)
Cash and cash equivalents, beginning of the period	75,799	47,663
Cash and cash equivalents, end of the period	49,753	45,304
Supplemental schedule of cash flow information
Interest paid	24,873	21,754
Income taxes paid	4,835	661
Redemption of Operating Partnership units held by noncontrolling interests for common stock:
Noncontrolling interests in Operating Partnership	(12)
Common stock and paid-in capital	12
Tax effect from vesting of restricted stock grants and option exercises
Other assets	272	644
Paid-in capital	(272)	(644)
Acquisitions of real estate assets
Real estate assets, net		11,009
Receivables from related parties and affiliated real estate joint ventures		$ (11,009)
Distribution of real estate from investments in unconsolidated real estate ventures
Real estate assets, net	17,261
Investments in unconsolidated real estate ventures	$ (17,261)

Organization

Organization	3 Months Ended
	Mar. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	1. ORGANIZATION 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 (“stores”) located throughout the United States. The Company continues the business of Extra Space Storage LLC and its subsidiaries, which had engaged in the self-storage business since 1977. The Company’s interests 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 has elected to be taxed as a REIT under the Internal Revenue Code of 1986, as amended. To the extent the Company continues to qualify as a REIT, it will not be subject to tax, with certain limited exceptions, on the taxable income that is distributed to its stockholders. The Company invests in stores by acquiring wholly-owned stores or by acquiring an equity interest in real estate entities. At March 31, 2016, the Company had direct and indirect equity interests in 1,018 stores. In addition, the Company managed 353 stores for third parties, bringing the total number of stores which it owns and/or manages to 1,371. These stores are located in 37 states, Washington, D.C. and Puerto Rico. The Company operates in three distinct segments: (1) rental operations; (2) tenant reinsurance; and (3) property management, acquisition and development. The rental operations activities include rental operations of stores in which we have an ownership interest. No single tenant accounts for more than 5.0% of rental income. Tenant reinsurance activities include the reinsurance of risks relating to the loss of goods stored by tenants in the Company’s stores. The Company’s property management, acquisition and development activities include managing, acquiring, developing and selling stores.

Basis of Presentation

Basis of Presentation	3 Months Ended
	Mar. 31, 2016
Accounting Policies [Abstract]
Basis of Presentation	2. BASIS OF PRESENTATION The accompanying unaudited condensed consolidated financial statements of the Company are presented on the accrual basis of accounting in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information, and in accordance with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they may not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, all adjustments (including normal recurring accruals) considered necessary for a fair presentation have been included. Operating results for the three months ended March 31, 2016, are not necessarily indicative of results that may be expected for the year ending December 31, 2016. The condensed consolidated balance sheet as of December 31, 2015 has been derived from the Company’s audited financial statements as of that date, but does not include all of the information and footnotes required by GAAP for complete financial statements. For further information refer to the consolidated financial statements and footnotes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2015, as filed with the Securities and Exchange Commission. Recently Issued Accounting Standards In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-09, “ Revenue from Contracts with Customers, In February 2015, the FASB issued ASU 2015-02, “ Consolidation (Topic 810): Amendments to the Consolidation Analysis.” In April 2015, the FASB issued ASU 2015-05, “ Intangibles – Goodwill and Other – Internal-Use Software (Subtopic 350-40) – Customers Accounting for Fees Paid in a Cloud Computing Arrangement, In February 2016, the FASB issued ASU 2016-02, “Leases (Topic 842),” In March 2016, the FASB issued ASU 2016-09, “ Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting

Fair Value Disclosures

Fair Value Disclosures	3 Months Ended
	Mar. 31, 2016
Fair Value Disclosures [Abstract]
Fair Value Disclosures	3. 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 FASB’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 the Company and its counterparties. However, as of March 31, 2016, the Company had assessed the significance of the impact of the credit valuation adjustments on the overall valuation of its derivative positions and determined that the credit valuation adjustments were not significant to the overall valuation of its derivatives. As a result, the Company determined that its derivative valuations in their entirety were 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 March 31, 2016, aggregated by the level in the fair value hierarchy within which those measurements fall. Fair Value Measurements at Reporting Date Using Description March 31, 2016 Quoted Prices in Active Significant Other Significant Other assets - Cash Flow Hedge Swap Agreements $ 463 $ — $ 463 $ — Other liabilities - Cash Flow Hedge Swap Agreements $ (34,708 ) $ — $ (34,708 ) $ — The Company did not have any significant assets or liabilities that are re-measured on a recurring basis using significant unobservable inputs as of March 31, 2016 or December 31, 2015. 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 carefully 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. 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. As of March 31, 2016, the Company had eight stores classified as held for sale. The estimated fair value less selling costs of each of these assets is greater than the carrying value of the assets, and therefore no loss has been recorded. The Company assesses whether there are any indicators that the value of the Company’s investments in unconsolidated real estate ventures may be impaired annually 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. In connection with the Company’s acquisition of stores, the purchase price is allocated to the tangible and intangible assets and liabilities acquired based on their 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 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. Debt assumed as part of an acquisition is recorded at fair value based on current interest rates compared to contractual rates. Acquisition-related transaction costs are expensed as incurred. 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, lines of credit and other liabilities reflected in the condensed consolidated balance sheets at March 31, 2016 and December 31, 2015 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 flows 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: March 31, 2016 December 31, 2015 Fair Carrying Fair Carrying Notes receivable from Preferred Operating Partnership unit holders $ 130,856 $ 120,230 $ 128,216 $ 120,230 Fixed rate notes receivable $ 85,927 $ 84,331 $ 86,814 $ 84,331 Fixed rate notes payable and notes payable to trusts $ 2,329,420 $ 2,271,925 $ 1,828,486 $ 1,806,904 Exchangeable senior notes $ 767,992 $ 640,725 $ 770,523 $ 660,364

Earnings Per Common Share

Earnings Per Common Share	3 Months Ended
	Mar. 31, 2016
Earnings Per Share [Abstract]
Earnings Per Common Share	4. 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 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 three months ended March 31, 2016 and 2015, options to purchase approximately 67,812 and 19,762 shares of common stock, respectively, were excluded from the computation of earnings per share as their effect would have been anti-dilutive. The following table presents the number of Preferred Operating Partnership units, and the potential common shares, that were excluded from the computation of earnings per share as their effect would have been anti-dilutive, assuming full conversion at the average share price for the quarter of $86.91. For the Three Months Ended March 31, 2016 2015 Number of Units Equivalent Shares Number of Units Equivalent Shares Series B Units 1,676,087 482,133 1,676,087 638,850 Series C Units 704,016 341,032 704,016 451,884 Series D Units 548,390 157,747 548,390 209,022 2,928,493 980,912 2,928,493 1,299,756 The Operating Partnership had $65,725 of its 2.375% Exchangeable Senior Notes due 2033 (the “2013 Notes”) issued and outstanding as of March 31, 2016. The 2013 Notes could potentially have a dilutive impact on the Company’s earnings per share calculations. The 2013 Notes are exchangeable by holders into shares of the Company’s common stock under certain circumstances per the terms of the indenture governing the 2013 Notes. The exchange price of the 2013 Notes was $54.87 per share as of March 31, 2016, 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 2013 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. The Operating Partnership had $575,000 of its 3.125% Exchangeable Senior Notes due 2035 (the “2015 Notes”) issued and outstanding as of March 31, 2016. 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 $95.40 per share as of March 31, 2016, 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. Although the Company has retained the right to satisfy the exchange obligation in excess of the accreted principal amount of the 2013 Notes and 2015 Notes in cash and/or common stock, Accounting Standards Codification (“ASC”) 260, “Earnings per Share,” 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 $115,000 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 $115,000 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. For the purposes of computing the diluted impact on earnings per share of the potential exchange of Series B 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 Series B Units outstanding as of March 31, 2016 of $41,902 by the closing price of the Company’s common stock as of March 31, 2016 of $93.46 per share. Assuming full exchange for common shares as of March 31, 2016, 448,342 shares would have been issued to the holders of the Series B Units. For the purposes of computing the diluted impact on earnings per share of the potential exchange of Series C 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 Series C Units outstanding as of March 31, 2016 of $29,639 by the closing price of the Company’s common stock as of March 31, 2016 of $93.46 per share. Assuming full exchange for common shares as of March 31, 2016, 317,130 shares would have been issued to the holders of the Series C Units. For the purposes of computing the diluted impact on earnings per share of the potential exchange of Series D 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 Series D Units outstanding as of March 31, 2016 of $13,710 by the closing price of the Company’s common stock as of March 31, 2016 of $93.46 per share. Assuming full exchange for common shares as of March 31, 2016, 146,694 shares would have been issued to the holders of the Series D Units. The computation of earnings per common share was as follows for the periods presented: For the Three Months Ended March 31, 2016 2015 Net income attributable to common stockholders $ 82,592 $ 53,742 Earnings and dividends allocated to participating securities (165 ) (119 ) Earnings for basic computations 82,427 53,623 Earnings and dividends allocated to participating securities — 119 Income allocated to noncontrolling interest - Preferred Operating Partnership (Series A Units) and Operating Partnership 5,474 3,635 Fixed component of income allocated to noncontrolling interest - Preferred Operating Partnership (Series A Units) (1,271 ) (1,274 ) Net income for diluted computations $ 86,630 $ 56,103 Weighted average common shares outstanding: Average number of common shares outstanding - basic 124,754,174 116,117,615 Series A Units 875,480 875,480 OP Units 5,621,470 4,365,879 Unvested restricted stock awards included for treasury stock method — 282,903 Shares related to exchangeable senior notes and dilutive stock options 704,970 953,841 Average number of common shares outstanding - diluted 131,956,094 122,595,718 Earnings per common share Basic $ 0.66 $ 0.46 Diluted $ 0.66 $ 0.46

Store Acquisitions

Store Acquisitions	3 Months Ended
	Mar. 31, 2016
Business Combinations [Abstract]
Store Acquisitions	5. STORE ACQUISITIONS The following table shows the Company’s acquisitions of operating stores for the three months ended March 31, 2016, and does not include purchases of raw land or improvements made to existing assets: Consideration Paid Fair Value Property Location Number of Date of Total Cash Paid Net Real estate New Mexico 1 3/29/2016 $ 10,958 $ 10,928 $ 30 $ 10,958 New Mexico 1 3/29/2016 17,940 17,905 35 17,940 Georgia 3 3/29/2016 25,087 25,069 18 25,087 Texas 1 3/21/2016 9,994 9,969 25 9,994 Illinois 1 2/25/2016 16,721 16,738 (17 ) 16,721 Massachusetts 1 2/16/2016 16,169 16,174 (5 ) 16,169 Florida, Maryland, Nevada, New York, Tennessee (1) 6 2/2/2016 53,898 53,940 (42 ) 98,082 Texas 3 1/14/2016 22,625 22,523 102 22,625 Florida 1 1/12/2016 9,001 8,980 21 9,001 Texas 3 1/7/2016 27,537 27,435 102 27,537 New Mexico 2 1/7/2016 15,607 15,495 112 15,607 2016 Totals 23 $ 225,537 $ 225,156 $ 381 $ 269,721 (1) - 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 45.04% of VRS, with the other 54.96% owned by affiliates of Prudential Real Estate (“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 54.96% 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 condensed consolidated statements of operations. Losses on Earnout from Prior Acquisition In 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 has been higher than expected, resulting in an increase in the estimate of the amount due to the sellers of $1,544, which was recorded as a loss and included in loss earnout from prior acquisitions in the Company’s condensed consolidated statements of operations for three months ended March 31, 2016.

Equity in Earnings of Unconsoli

Equity in Earnings of Unconsolidated Real Estate Ventures - Gain on Sale of Real Estate and Purchase of Joint Venture Partners' Interests	3 Months Ended
	Mar. 31, 2016
Equity in Earnings of Unconsolidated Real Estate Ventures - Gain on Sale of Real Estate and Purchase of Joint Venture Partners' Interests	14. EQUITY IN EARNINGS OF UNCONSOLIDATED REAL ESTATE VENTURES—GAIN ON SALE OF REAL ESTATE AND PURCHASE OF JOINT VENTURE PARTNERS’ INTERESTS On February 2, 2016, the Company acquired six operating stores from VRS in a step acquisition. The Company recognized a non-cash gain of $26,923 related to this transaction as a result of revaluing its existing equity interest upon the purchase of the remaining interest. See the Store Acquisitions footnote for more information. In March 2015, ESS PRISA II LLC (“PRISA II”), a joint venture in which the Company holds a 2.0% interest, sold one store located in New York for $90,000. As a result of the sale, PRISA II recognized a gain of $60,496 and the Company recorded its 2.0% portion of the gain, or $1,228. In March 2015, the Company acquired its joint venture partner’s 82.4% interest in Sacramento One, an existing joint venture which owned one store located in California, for $1,700. In addition, the Company held mortgage notes receivable from Sacramento One totaling $11,009, which were written off as part of the total consideration. Prior to the acquisition, the remaining 17.6% interest was owned by the Company, which accounted for its investment in Sacramento One using the equity method. The Company recorded a non-cash gain of $1,629 related to this transaction, which represents the increase in fair value of the Company’s interest in the joint venture from its formation to the acquisition date.
Baychester Investments LLC [Member]
Equity in Earnings of Unconsolidated Real Estate Ventures - Gain on Sale of Real Estate and Purchase of Joint Venture Partners' Interests	6. INVESTMENTS IN UNCONSOLIDATED REAL ESTATE VENTURES On March 31, 2016, the Company entered into a new joint venture, ESS-H Baychester Investments LLC (“Baychester”). Baychester owns a single store in New York. The Company contributed $4,794 for a 44.4% interest in Baychester. The Company accounts for its investment in Baychester under the equity method of accounting.

Variable Interests

Variable Interests	3 Months Ended
	Mar. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Variable Interests	7. VARIABLE INTERESTS The Operating Partnership has three wholly-owned unconsolidated subsidiaries (“Trust,” “Trust II” and “Trust III,” together, the “Trusts”) that have issued trust preferred securities to third parties and common securities to the Operating Partnership. The proceeds from the sale of the preferred and common securities were loaned in the form of notes to the Operating Partnership. 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 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 for the proceeds as discussed above, which are owed to the Trusts. The Company has also included its investment in the Trusts’ common securities in other assets on the condensed consolidated balance sheets. 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 equal to the notes payable that the Trusts owe to third parties for their investments in the Trusts’ preferred securities. Following is a tabular comparison of the assets and liabilities the Company has recorded as a result of its involvement with the Trusts to the maximum exposure to loss the Company is subject to as a result of such involvement as of March 31, 2016: Notes payable Investment Maximum Difference Trust $ 36,083 $ 1,083 $ 35,000 $ — Trust II 42,269 1,269 41,000 — Trust III 41,238 1,238 40,000 — 119,590 3,590 116,000 — Unamortized debt issuance costs (2,365 ) $ 117,225 $ 3,590 $ 116,000 $ — The Company had no consolidated VIEs during the three months ended March 31, 2016.

Derivatives

Derivatives	3 Months Ended
	Mar. 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives	8. DERIVATIVES The Company is exposed to certain risks 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 by using derivative financial instruments. Specifically, the Company enters into derivative financial instruments to manage exposure that arises 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 these objectives, 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 three months ended March 31, 2016 and 2015, such derivatives were used to hedge the variable cash flows associated with existing variable-rate debt. During the remainder of 2016, the Company estimates that an additional $16,403 will be reclassified as an increase to interest expense. The Company held 29 derivative financial instruments which had a total combined notional amount of $1,850,111 as of March 31, 2016. 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 condensed consolidated balance sheets: Asset (Liability) Derivatives March 31, 2016 December 31, 2015 Derivatives designated as hedging instruments: Fair Value Other assets $ 463 $ 4,996 Other liabilities $ (34,708 ) $ (6,991 ) Effect of Derivative Instruments The tables below present the effect of the Company’s derivative financial instruments on the condensed consolidated statements of operations for the periods presented. No tax effect has been presented as the derivative instruments are held by the Company: Classification of Income (Expense) For the Three Months Ended March 31, Type 2016 2015 Swap Agreements Interest expense $ (4,454 ) $ (2,297 ) Gain (loss) recognized in OCI Location of amounts reclassified from OCI into income Gain (loss) reclassifed from OCI Type 2016 2015 2016 2015 Swap Agreements $ (34,960 ) $ (8,875 ) Interest expense $ (4,454 ) $ (2,297 ) 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 March 31, 2016, 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 $34,708. As of March 31, 2016, the Company had not posted any collateral related to these agreements. If the Company had breached any of these provisions as of March 31, 2016, it could have been required to settle its obligations under the agreements at their termination value of $37,240 including accrued interest.

Exchangeable Senior Notes

Exchangeable Senior Notes	3 Months Ended
	Mar. 31, 2016
Text Block [Abstract]
Exchangeable Senior Notes	9. 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% 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 condensed 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 March 31, 2016 was approximately 10.48 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. On June 21, 2013, the Operating Partnership issued $250,000 of its 2.375% Exchangeable Senior Notes due 2033 at a 1.5% discount, or $3,750. Costs incurred to issue the 2013 Notes were approximately $1,672. 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 condensed consolidated balance sheets. The 2013 Notes are general unsecured senior obligations of the Operating Partnership and are fully guaranteed by the Company. Interest is payable on January 1 and July 1 of each year beginning January 1, 2014, until the maturity date of July 1, 2033. The 2013 Notes bear interest at 2.375% per annum and contain an exchange settlement feature, which provides that the 2013 Notes may, under certain circumstances, be exchangeable for cash (for the principal amount of the 2013 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 2013 Notes as of March 31, 2016 was approximately 18.22 shares of the Company’s common stock per $1,000 principal amount of the 2013 Notes. The Operating Partnership may redeem the 2013 Notes at any time to preserve the Company’s status as a REIT. In addition, on or after July 5, 2018, the Operating Partnership may redeem the 2013 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 2013 Notes. The holders of the 2013 Notes have the right to require the Operating Partnership to repurchase the 2013 Notes for cash, in whole or in part, on July 1 of the years 2018, 2023 and 2028, and upon the occurrence of certain designated events, in each case for a repurchase price equal to 100% of the principal amount of the 2013 Notes plus accrued and unpaid interest. Certain events are considered “Events of Default,” as defined in the indenture governing the 2013 Notes, which may result in the accelerated maturity of the 2013 Notes. Additionally, the 2013 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 exceeded 130% of the exchange price for the required time period for the 2013 Notes during the quarter ended March 31, 2016. Therefore, holders of the 2013 Notes may elect to exchange such notes during the quarter ended June 30, 2016. 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 components of the 2013 Notes and 2015 Notes separately. The equity components are included in paid-in capital in stockholders’ equity in the condensed 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 discounts are being amortized as interest expense over the remaining period of the debt through its first redemption date: July 1, 2018 for the 2013 Notes, and October 1, 2020 for the 2015 Notes. The effective interest rate on the liability components of both the 2013 Notes and 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 Company’s 2013 Notes and 2015 Notes, including the total carrying amounts of the equity components, the principal amounts of the liability components, the unamortized discounts and the net carrying amounts was as follows for the periods indicated: March 31, 2016 December 31, 2015 Carrying amount of equity component - 2013 Notes $ — $ — Carrying amount of equity component - 2015 Notes 22,597 22,597 Carrying amount of equity components $ 22,597 $ 22,597 Principal amount of liability component 2013 Notes $ 65,725 $ 85,364 Principal amount of liability component 2015 Notes 575,000 575,000 Unamortized discount - equity component - 2013 Notes (1,827 ) (2,605 ) Unamortized discount - equity component - 2015 Notes (20,533 ) (21,565 ) Unamortized cash discount - 2013 Notes (438 ) (633 ) Unamortized debt issuance costs (11,040 ) (11,698 ) Net carrying amount of liability components $ 606,887 $ 623,863 The amount of interest cost recognized relating to the contractual interest rates and the amortization of the discounts on the liability components of the Notes were as follows for the periods indicated: For the Three Months Ended March 31, 2016 2015 Contractual interest $ 4,882 $ 1,484 Amortization of discount 1,233 697 Total interest expense recognized $ 6,115 $ 2,181 Repurchases of 2013 Notes During February 2016, the Company repurchased a total principal amount of $19,639 of the 2013 Notes. The Company paid cash for the principal amount, and issued a total of 130,909 shares of common stock valued at $11,380 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 repurchase is as follows: February 2016 Principal amount repurchased $ 19,639 Amount allocated to: Extinguishment of liability component $ 18,887 Reacquisition of equity component 12,132 Total consideration paid for repurchase $ 31,019 Exchangeable senior notes repurchased $ 19,639 Extinguishment of liability component (18,887 ) Discount on exchangeable senior notes (716 ) Related debt issuance costs (36 ) Gain/(loss) on repurchase $ —

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2016
Equity [Abstract]
Stockholders' Equity	10. STOCKHOLDERS’ EQUITY 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. During the three months ended March 31, 2016, the Company sold 831,300 shares of common stock at an average sales price of $89.66 per share, resulting in net proceeds of $73,574.

Noncontrolling Interests

Noncontrolling Interests	3 Months Ended
	Mar. 31, 2016
Noncontrolling Interests	13. OTHER NONCONTROLLING INTERESTS Other noncontrolling interests represent the ownership interest of third parties in two consolidated joint ventures as of March 31, 2016. One of these consolidated joint ventures owns a single operating store in California, and the other owns a store under development in Texas. The voting interests of the third-party owners range from 17.5% to 20.0%. Other noncontrolling interests are included in the stockholders’ equity section of the Company’s condensed consolidated balance sheets. The income or losses attributable to this third-party owner based on its ownership percentage are reflected in net income allocated to Operating Partnership and other noncontrolling interests in the condensed consolidated statements of operations. On June 11, 2015, the Company purchased its joint venture partner’s remaining 1% interest in an existing joint venture for $1,267. The joint venture owned 19 properties in California, Florida, Nevada, Ohio, Pennsylvania, Tennessee, Texas and Virginia, and as a result of this purchase, these properties became wholly-owned by the Company. Prior to this acquisition, the partner’s interest was reported in other noncontrolling interests. Since the Company retained its controlling interest in the subsidiary, this transaction was accounted for as an equity transaction. The carrying amount of the noncontrolling interest was reduced to zero to reflect the purchase, and the difference between the price paid by the Company and the carrying value of the noncontrolling interest was recorded as an adjustment to equity attributable to the Company.
Common Operating Partnership [Member]
Noncontrolling Interests	12. NONCONTROLLING INTEREST IN OPERATING PARTNERSHIP The Company’s interest in its stores is held through the Operating Partnership. ESS Holding Business Trust I, a wholly-owned subsidiary of the Company, is the sole general partner of the Operating Partnership. ESS Holding Business Trust II, also a wholly-owned subsidiary of the Company, is a limited partner of the Operating Partnership. Between its general partner and limited partner interests, the Company held a 93.0% ownership interest in the Operating Partnership as of March 31, 2016. The remaining ownership interests in the Operating Partnership (including Preferred Operating Partnership units) of 7.0% 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. In conjunction with the formation of the Company, and as a result of subsequent acquisitions, certain persons and entities contributing interests in stores to the Operating Partnership received limited partnership interests in the form of OP Units. Limited partners who received OP Units in the formation transactions or in exchange for contributions for interests in stores have the right to require the Operating Partnership to redeem part or all of their OP Units for 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, in 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 Partnership Agreement. The ten-day average closing stock price at March 31, 2016 was $90.76 and there were 5,621,322 OP Units outstanding. Assuming that all of the OP Unit holders exercised their right to redeem all of their OP Units on March 31, 2016 and the Company elected to pay the OP Unit holders cash, the Company would have paid $510,191 in cash consideration to redeem the 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 OP Units and classifies the noncontrolling interest represented by the OP Units as stockholders’ equity in the accompanying condensed 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 condensed 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 and (2) the redemption value as of the end of the period in which the determination is made.
Preferred Operating Partnership Units [Member]
Noncontrolling Interests	11. 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 condensed consolidated balance sheets. The Company will periodically evaluate individual noncontrolling interests for the ability to continue to recognize the noncontrolling interest as permanent equity in the condensed 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 and (2) the redemption value as of the end of the period in which the determination is made. Series A Participating Redeemable Preferred Units On June 15, 2007, the Operating Partnership entered into a Contribution Agreement with various limited partnerships affiliated with AAAAA Rent-A-Space to acquire ten stores in exchange for 989,980 Series A Units of the Operating Partnership. The stores are located in California and Hawaii. The partnership agreement of the Operating Partnership (as amended, the “Partnership Agreement”) provides for the designation and issuance of the Series A Units. The Series A Units will have priority over all other partnership interests of the Operating Partnership with respect to distributions and liquidation. Under the Partnership Agreement, Series A Units in the amount of $115,000 bear a fixed priority return of 5% and have a fixed liquidation value of $115,000. The remaining balance participates in distributions with, and has a liquidation value equal to, that of the OP Units. The Series A Units are redeemable at the option of the holder, which redemption obligation may be satisfied, at the Company’s option, in cash or shares of its common stock. On June 25, 2007, the Operating Partnership loaned the holders of the Series A Units $100,000. The note receivable bears interest at 4.85%. During 2013, a loan amendment was signed extending the maturity date to September 1, 2020. The loan is secured by the borrower’s Series A Units. The holders of the Series A Units could redeem up to 114,500 Series A Units prior to the maturity date of the loan. If any redemption in excess of 114,500 Series A Units occurs prior to the maturity date, the holder of the Series A Units is required to repay the loan as of the date of that redemption. On October 3, 2014, the holders of the Series A Units redeemed 114,500 Series A Units for $4,794 in cash and 280,331 shares of common stock. No additional redemption of Series A Units can be made without repayment of the loan. The Series A Units are shown on the balance sheet net of the $100,000 loan because the borrower under the loan receivable is also the holder of the Series A Units. Series B Redeemable Preferred Units On April 3, 2014, the Operating Partnership completed the purchase of a store located in Georgia. This store was acquired in exchange for $15,158 of cash and 333,360 Series B Units valued at $8,334. On August 29, 2013, the Operating Partnership completed the purchase of 19 out of 20 stores affiliated with All Aboard Mini Storage, all of which are located in California. On September 26, 2013, the Operating Partnership completed the purchase of the remaining store. These stores were acquired in exchange for $100,876 of cash (including $98,960 of debt assumed and immediately defeased at closing), 1,342,727 Series B Units valued at $33,568, and 1,448,108 OP Units valued at $62,341. 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 outstanding Series B Units have a liquidation value of $25.00 per unit for a fixed liquidation value of $41,902. Holders of the Series B Units receive distributions at an annual rate of 6.0%. These distributions are cumulative. The Series B Units became 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. Series C Convertible Redeemable Preferred Units On November 19, 2013, the Company entered into Contribution Agreements with various entities affiliated with Grupe Properties Co. Inc. (“Grupe”), under which the Company agreed to acquire twelve stores, all of which are located in California. The Company completed the purchase of these stores between December 2013 and May 2014. The Company previously held 35% interests in five of these stores and a 40% interest in one store through six separate joint ventures with Grupe. These stores were acquired in exchange for a total of approximately $45,722 of cash, the assumption of $37,532 in existing debt, and the issuance of 704,016 Series C Units valued at $30,960. 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 outstanding Series C Units have a liquidation value of $42.10 per unit for a fixed liquidation value of $29,639. From issuance to the fifth anniversary of issuance, each Series C Unit holder will receive quarterly distributions equal to the quarterly distribution per 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 OP Units at the option of the holder one year from the date of issuance, at a rate of 0.9145 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 certain holders of the Series C Units $20,230. The notes receivable, which are collateralized by the Series C Units, bear interest at 5.0% per annum and mature on December 15, 2024. The Series C Units are shown on the balance sheet net of the $20,230 loan because the borrower under the loan receivable is also the holder of the Series C units. Series D Redeemable Preferred Units In December 2014, the Operating Partnership completed the acquisition of a store located in Florida. This store was acquired in exchange for $5,621 in cash and 548,390 Series D Units valued at $13,710. 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 interests of the Operating Partnership with respect to distributions and liquidation. The Series D Units have a liquidation value of $25.00 per unit, for a fixed liquidation value of $13,710. Holders of the Series D Units receive distributions at an annual rate of 5.0%. These distributions are cumulative. The Series D Units became 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.

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2016
Segment Reporting [Abstract]
Segment Information	15. SEGMENT INFORMATION The Company operates in three distinct segments: (1) rental operations; (2) tenant reinsurance; and (3) property management, acquisition and development. Management fees collected for wholly-owned stores are eliminated in consolidation. Financial information for the Company’s business segments is presented below: March 31, 2016 December 31, 2015 Balance Sheet Investment in unconsolidated real estate ventures Rental operations $ 89,224 $ 103,007 Total assets Rental operations $ 5,901,210 $ 5,674,030 Tenant reinsurance 34,180 37,696 Property management, acquisition and development 356,029 359,681 $ 6,291,419 $ 6,071,407 For the Three Months Ended March 31, 2016 2015 Statement of Operations Total revenues Rental operations $ 199,488 $ 148,894 Tenant reinsurance 20,555 16,510 Property management, acquisition and development 9,360 7,750 229,403 173,154 Operating expenses, including depreciation and amortization Rental operations 101,698 75,509 Tenant reinsurance 4,311 2,928 Property management, acquisition and development 29,766 19,281 135,775 97,718 Income (loss) from operations Rental operations 97,790 73,385 Tenant reinsurance 16,244 13,582 Property management, acquisition and development (20,406 ) (11,531 ) 93,628 75,436 Loss on earnout from prior acquisition Property management, acquisition and development (1,544 ) — Interest expense Rental operations (30,565 ) (21,157 ) Property management, acquisition and development (794 ) (274 ) (31,359 ) (21,431 ) Non-cash interest expense related to the amortization of discount on equity component of exchangeable senior notes Property management, acquisition and development (1,233 ) (697 ) Interest income Tenant reinsurance 3 4 Property management, acquisition and development 1,711 852 1,714 856 Interest income on note receivable from Preferred Operating Partnership unit holder Property management, acquisition and development 1,213 1,213 Equity in earnings of unconsolidated real estate ventures Rental operations 2,830 2,650 Equity in earnings of unconsolidated real estate ventures - gain on sale of real estate assets and purchase of partners’ interests Property management, acquisition and development 26,923 2,857 Income tax (expense) benefit Rental operations (845 ) (754 ) Tenant reinsurance (2,663 ) (1,874 ) Property management, acquisition and development 743 380 (2,765 ) (2,248 ) Net income (loss) Rental operations 69,210 54,124 Tenant reinsurance 13,584 11,712 Property management, acquisition and development 6,613 (7,200 ) $ 89,407 $ 58,636 Depreciation and amortization expense Rental operations $ 40,586 $ 28,265 Property management, acquisition and development 2,311 2,163 $ 42,897 $ 30,428 Statement of Cash Flows Acquisition of real estate assets Property management, acquisition and development $ (234,820 ) $ (77,082 ) Development and redevelopment of real estate assets Property management, acquisition and development $ (6,543 ) $ (3,140 )

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	16. COMMITMENTS AND CONTINGENCIES As of March 31, 2016, 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. Therefore, any estimate(s) of loss disclosed below represents what management believes to be an estimate of loss only for certain matters meeting these criteria and does not represent the Company’s maximum loss exposure. 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. The Company currently has a legal proceeding pending against it that includes causes of action alleging wrongful foreclosure, violations of various state specific self-storage statutes, and violations of various consumer fraud acts. As a result of this litigation matter, the Company recorded a liability of $4,000 during the three months ended March 31, 2016, which is included in other liabilities on the condensed consolidated balance sheet. As of March 31, 2016, the Company was under contract to acquire 21 operating stores and nine stores to be acquired upon the completion of construction, for a total purchase price of $349,376. Of these stores, 26 are scheduled to close in 2016. The remaining stores will close upon completion of construction, expected to occur on various dates in 2017 and 2018. Additionally, the Company is under contract to acquire 10 stores with joint venture partners, for a total purchase price of $302,800. Seven of those stores are scheduled to close in 2016 while the remaining three stores are expected to close in 2017 and 2018. 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.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2016
Subsequent Events [Abstract]
Subsequent Events	17. SUBSEQUENT EVENTS Subsequent to March 31, 2016, the Company has purchased 10 stores for a total purchase price of $88,048. These stores are located in Arizona, Colorado, Hawaii, Indiana and Texas. On April 20, 2016, the Company sold seven stores located in Ohio and Indiana that had been classified as held for sale for $18,000.

Basis of Presentation (Policies

Basis of Presentation (Policies)	3 Months Ended
	Mar. 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Recently Issued Accounting Standards	Recently Issued Accounting Standards In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-09, “ Revenue from Contracts with Customers, In February 2015, the FASB issued ASU 2015-02, “ Consolidation (Topic 810): Amendments to the Consolidation Analysis.” In April 2015, the FASB issued ASU 2015-05, “ Intangibles – Goodwill and Other – Internal-Use Software (Subtopic 350-40) – Customers Accounting for Fees Paid in a Cloud Computing Arrangement, In February 2016, the FASB issued ASU 2016-02, “Leases (Topic 842),” In March 2016, the FASB issued ASU 2016-09, “ Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting
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 FASB’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 the Company and its counterparties. However, as of March 31, 2016, the Company had assessed the significance of the impact of the credit valuation adjustments on the overall valuation of its derivative positions and determined that the credit valuation adjustments were not significant to the overall valuation of its derivatives. As a result, the Company determined that its derivative valuations in their entirety were 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 March 31, 2016, aggregated by the level in the fair value hierarchy within which those measurements fall. Fair Value Measurements at Reporting Date Using Description March 31, 2016 Quoted Prices in Active Significant Other Significant Other assets - Cash Flow Hedge Swap Agreements $ 463 $ — $ 463 $ — Other liabilities - Cash Flow Hedge Swap Agreements $ (34,708 ) $ — $ (34,708 ) $ — The Company did not have any significant assets or liabilities that are re-measured on a recurring basis using significant unobservable inputs as of March 31, 2016 or December 31, 2015. 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 carefully 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. 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. As of March 31, 2016, the Company had eight stores classified as held for sale. The estimated fair value less selling costs of each of these assets is greater than the carrying value of the assets, and therefore no loss has been recorded. The Company assesses whether there are any indicators that the value of the Company’s investments in unconsolidated real estate ventures may be impaired annually 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. In connection with the Company’s acquisition of stores, the purchase price is allocated to the tangible and intangible assets and liabilities acquired based on their 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 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. Debt assumed as part of an acquisition is recorded at fair value based on current interest rates compared to contractual rates. Acquisition-related transaction costs are expensed as incurred. 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, lines of credit and other liabilities reflected in the condensed consolidated balance sheets at March 31, 2016 and December 31, 2015 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 flows 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: March 31, 2016 December 31, 2015 Fair Carrying Fair Carrying Notes receivable from Preferred Operating Partnership unit holders $ 130,856 $ 120,230 $ 128,216 $ 120,230 Fixed rate notes receivable $ 85,927 $ 84,331 $ 86,814 $ 84,331 Fixed rate notes payable and notes payable to trusts $ 2,329,420 $ 2,271,925 $ 1,828,486 $ 1,806,904 Exchangeable senior notes $ 767,992 $ 640,725 $ 770,523 $ 660,364
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 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 three months ended March 31, 2016 and 2015, options to purchase approximately 67,812 and 19,762 shares of common stock, respectively, were excluded from the computation of earnings per share as their effect would have been anti-dilutive. The following table presents the number of Preferred Operating Partnership units, and the potential common shares, that were excluded from the computation of earnings per share as their effect would have been anti-dilutive, assuming full conversion at the average share price for the quarter of $86.91. For the Three Months Ended March 31, 2016 2015 Number of Units Equivalent Shares Number of Units Equivalent Shares Series B Units 1,676,087 482,133 1,676,087 638,850 Series C Units 704,016 341,032 704,016 451,884 Series D Units 548,390 157,747 548,390 209,022 2,928,493 980,912 2,928,493 1,299,756 The Operating Partnership had $65,725 of its 2.375% Exchangeable Senior Notes due 2033 (the “2013 Notes”) issued and outstanding as of March 31, 2016. The 2013 Notes could potentially have a dilutive impact on the Company’s earnings per share calculations. The 2013 Notes are exchangeable by holders into shares of the Company’s common stock under certain circumstances per the terms of the indenture governing the 2013 Notes. The exchange price of the 2013 Notes was $54.87 per share as of March 31, 2016, 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 2013 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. The Operating Partnership had $575,000 of its 3.125% Exchangeable Senior Notes due 2035 (the “2015 Notes”) issued and outstanding as of March 31, 2016. 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 $95.40 per share as of March 31, 2016, 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. Although the Company has retained the right to satisfy the exchange obligation in excess of the accreted principal amount of the 2013 Notes and 2015 Notes in cash and/or common stock, Accounting Standards Codification (“ASC”) 260, “Earnings per Share,” 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 $115,000 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 $115,000 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. For the purposes of computing the diluted impact on earnings per share of the potential exchange of Series B 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 Series B Units outstanding as of March 31, 2016 of $41,902 by the closing price of the Company’s common stock as of March 31, 2016 of $93.46 per share. Assuming full exchange for common shares as of March 31, 2016, 448,342 shares would have been issued to the holders of the Series B Units. For the purposes of computing the diluted impact on earnings per share of the potential exchange of Series C 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 Series C Units outstanding as of March 31, 2016 of $29,639 by the closing price of the Company’s common stock as of March 31, 2016 of $93.46 per share. Assuming full exchange for common shares as of March 31, 2016, 317,130 shares would have been issued to the holders of the Series C Units. For the purposes of computing the diluted impact on earnings per share of the potential exchange of Series D 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 Series D Units outstanding as of March 31, 2016 of $13,710 by the closing price of the Company’s common stock as of March 31, 2016 of $93.46 per share. Assuming full exchange for common shares as of March 31, 2016, 146,694 shares would have been issued to the holders of the Series D Units.
Derivatives	The Company is exposed to certain risks 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 by using derivative financial instruments. Specifically, the Company enters into derivative financial instruments to manage exposure that arises 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.
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 components of the 2013 Notes and 2015 Notes separately. The equity components are included in paid-in capital in stockholders’ equity in the condensed 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 discounts are being amortized as interest expense over the remaining period of the debt through its first redemption date: July 1, 2018 for the 2013 Notes, and October 1, 2020 for the 2015 Notes. The effective interest rate on the liability components of both the 2013 Notes and 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.

Fair Value Disclosures (Tables)

Fair Value Disclosures (Tables)	3 Months Ended
	Mar. 31, 2016
Fair Value Disclosures [Abstract]
Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis	The table below presents the Company’s assets and liabilities measured at fair value on a recurring basis as of March 31, 2016, aggregated by the level in the fair value hierarchy within which those measurements fall. Fair Value Measurements at Reporting Date Using Description March 31, 2016 Quoted Prices in Active Significant Other Significant Other assets - Cash Flow Hedge Swap Agreements $ 463 $ — $ 463 $ — Other liabilities - Cash Flow Hedge Swap Agreements $ (34,708 ) $ — $ (34,708 ) $ —
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: March 31, 2016 December 31, 2015 Fair Carrying Fair Carrying Notes receivable from Preferred Operating Partnership unit holders $ 130,856 $ 120,230 $ 128,216 $ 120,230 Fixed rate notes receivable $ 85,927 $ 84,331 $ 86,814 $ 84,331 Fixed rate notes payable and notes payable to trusts $ 2,329,420 $ 2,271,925 $ 1,828,486 $ 1,806,904 Exchangeable senior notes $ 767,992 $ 640,725 $ 770,523 $ 660,364

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	3 Months Ended
	Mar. 31, 2016
Earnings Per Share [Abstract]
Schedule of Antidilutive Shares Excluded from Computation of Earnings Per Share	The following table presents the number of Preferred Operating Partnership units, and the potential common shares, that were excluded from the computation of earnings per share as their effect would have been anti-dilutive, assuming full conversion at the average share price for the quarter of $86.91. For the Three Months Ended March 31, 2016 2015 Number of Units Equivalent Shares Number of Units Equivalent Shares Series B Units 1,676,087 482,133 1,676,087 638,850 Series C Units 704,016 341,032 704,016 451,884 Series D Units 548,390 157,747 548,390 209,022 2,928,493 980,912 2,928,493 1,299,756
Schedule of Computation of Earnings Per Common Share	The computation of earnings per common share was as follows for the periods presented: For the Three Months Ended March 31, 2016 2015 Net income attributable to common stockholders $ 82,592 $ 53,742 Earnings and dividends allocated to participating securities (165 ) (119 ) Earnings for basic computations 82,427 53,623 Earnings and dividends allocated to participating securities — 119 Income allocated to noncontrolling interest - Preferred Operating Partnership (Series A Units) and Operating Partnership 5,474 3,635 Fixed component of income allocated to noncontrolling interest - Preferred Operating Partnership (Series A Units) (1,271 ) (1,274 ) Net income for diluted computations $ 86,630 $ 56,103 Weighted average common shares outstanding: Average number of common shares outstanding - basic 124,754,174 116,117,615 Series A Units 875,480 875,480 OP Units 5,621,470 4,365,879 Unvested restricted stock awards included for treasury stock method — 282,903 Shares related to exchangeable senior notes and dilutive stock options 704,970 953,841 Average number of common shares outstanding - diluted 131,956,094 122,595,718 Earnings per common share Basic $ 0.66 $ 0.46 Diluted $ 0.66 $ 0.46

Store Acquisitions (Tables)

Store Acquisitions (Tables)	3 Months Ended
	Mar. 31, 2016
Business Combinations [Abstract]
Schedule of Operating Properties Acquired	The following table shows the Company’s acquisitions of operating stores for the three months ended March 31, 2016, and does not include purchases of raw land or improvements made to existing assets: Consideration Paid Fair Value Property Location Number of Date of Total Cash Paid Net Real estate New Mexico 1 3/29/2016 $ 10,958 $ 10,928 $ 30 $ 10,958 New Mexico 1 3/29/2016 17,940 17,905 35 17,940 Georgia 3 3/29/2016 25,087 25,069 18 25,087 Texas 1 3/21/2016 9,994 9,969 25 9,994 Illinois 1 2/25/2016 16,721 16,738 (17 ) 16,721 Massachusetts 1 2/16/2016 16,169 16,174 (5 ) 16,169 Florida, Maryland, Nevada, New York, Tennessee (1) 6 2/2/2016 53,898 53,940 (42 ) 98,082 Texas 3 1/14/2016 22,625 22,523 102 22,625 Florida 1 1/12/2016 9,001 8,980 21 9,001 Texas 3 1/7/2016 27,537 27,435 102 27,537 New Mexico 2 1/7/2016 15,607 15,495 112 15,607 2016 Totals 23 $ 225,537 $ 225,156 $ 381 $ 269,721 (1) - 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 45.04% of VRS, with the other 54.96% owned by affiliates of Prudential Real Estate (“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 54.96% 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 condensed consolidated statements of operations.

Variable Interests (Tables)

Variable Interests (Tables)	3 Months Ended
	Mar. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Assets and Liabilities and Maximum Exposure to Loss Related to Trusts	Following is a tabular comparison of the assets and liabilities the Company has recorded as a result of its involvement with the Trusts to the maximum exposure to loss the Company is subject to as a result of such involvement as of March 31, 2016: Notes payable Investment Maximum Difference Trust $ 36,083 $ 1,083 $ 35,000 $ — Trust II 42,269 1,269 41,000 — Trust III 41,238 1,238 40,000 — 119,590 3,590 116,000 — Unamortized debt issuance costs (2,365 ) $ 117,225 $ 3,590 $ 116,000 $ —

Derivatives (Tables)

Derivatives (Tables)	3 Months Ended
	Mar. 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
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 condensed consolidated balance sheets: Asset (Liability) Derivatives March 31, 2016 December 31, 2015 Derivatives designated as hedging instruments: Fair Value Other assets $ 463 $ 4,996 Other liabilities $ (34,708 ) $ (6,991 )
Interest Payments Recognized as an Increase or Decrease in Interest Expense	The tables below present the effect of the Company’s derivative financial instruments on the condensed consolidated statements of operations for the periods presented. No tax effect has been presented as the derivative instruments are held by the Company: Classification of Income (Expense) For the Three Months Ended March 31, Type 2016 2015 Swap Agreements Interest expense $ (4,454 ) $ (2,297 )
Schedule of Information Relating to Gain (Loss) Recognized on Swap Agreements	Gain (loss) recognized in OCI Location of amounts reclassified from OCI into income Gain (loss) reclassifed from OCI Type 2016 2015 2016 2015 Swap Agreements $ (34,960 ) $ (8,875 ) Interest expense $ (4,454 ) $ (2,297 )

Exchangeable Senior Notes (Tabl

Exchangeable Senior Notes (Tables)	3 Months Ended
	Mar. 31, 2016
Text Block [Abstract]
Schedule of Information about Total Carrying Amounts of Equity Components, Principal Amounts of Liability Components, Unamortized Discounts and Net Carrying Amounts for Notes	Information about the Company’s 2013 Notes and 2015 Notes, including the total carrying amounts of the equity components, the principal amounts of the liability components, the unamortized discounts and the net carrying amounts was as follows for the periods indicated: March 31, 2016 December 31, 2015 Carrying amount of equity component - 2013 Notes $ — $ — Carrying amount of equity component - 2015 Notes 22,597 22,597 Carrying amount of equity components $ 22,597 $ 22,597 Principal amount of liability component 2013 Notes $ 65,725 $ 85,364 Principal amount of liability component 2015 Notes 575,000 575,000 Unamortized discount - equity component - 2013 Notes (1,827 ) (2,605 ) Unamortized discount - equity component - 2015 Notes (20,533 ) (21,565 ) Unamortized cash discount - 2013 Notes (438 ) (633 ) Unamortized debt issuance costs (11,040 ) (11,698 ) Net carrying amount of liability components $ 606,887 $ 623,863
Summary of Amount of Interest Cost Recognized Relating to Contractual Interest Rates and Amortization of Discounts on Liability Components of Notes	The amount of interest cost recognized relating to the contractual interest rates and the amortization of the discounts on the liability components of the Notes were as follows for the periods indicated: For the Three Months Ended March 31, 2016 2015 Contractual interest $ 4,882 $ 1,484 Amortization of discount 1,233 697 Total interest expense recognized $ 6,115 $ 2,181
Summary of Repurchase of Debt	Information about the repurchase is as follows: February 2016 Principal amount repurchased $ 19,639 Amount allocated to: Extinguishment of liability component $ 18,887 Reacquisition of equity component 12,132 Total consideration paid for repurchase $ 31,019 Exchangeable senior notes repurchased $ 19,639 Extinguishment of liability component (18,887 ) Discount on exchangeable senior notes (716 ) Related debt issuance costs (36 ) Gain/(loss) on repurchase $ —

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2016
Segment Reporting [Abstract]
Schedule of Financial Information of Business Segments	Financial information for the Company’s business segments is presented below: March 31, 2016 December 31, 2015 Balance Sheet Investment in unconsolidated real estate ventures Rental operations $ 89,224 $ 103,007 Total assets Rental operations $ 5,901,210 $ 5,674,030 Tenant reinsurance 34,180 37,696 Property management, acquisition and development 356,029 359,681 $ 6,291,419 $ 6,071,407 For the Three Months Ended March 31, 2016 2015 Statement of Operations Total revenues Rental operations $ 199,488 $ 148,894 Tenant reinsurance 20,555 16,510 Property management, acquisition and development 9,360 7,750 229,403 173,154 Operating expenses, including depreciation and amortization Rental operations 101,698 75,509 Tenant reinsurance 4,311 2,928 Property management, acquisition and development 29,766 19,281 135,775 97,718 Income (loss) from operations Rental operations 97,790 73,385 Tenant reinsurance 16,244 13,582 Property management, acquisition and development (20,406 ) (11,531 ) 93,628 75,436 Loss on earnout from prior acquisition Property management, acquisition and development (1,544 ) — Interest expense Rental operations (30,565 ) (21,157 ) Property management, acquisition and development (794 ) (274 ) (31,359 ) (21,431 ) Non-cash interest expense related to the amortization of discount on equity component of exchangeable senior notes Property management, acquisition and development (1,233 ) (697 ) Interest income Tenant reinsurance 3 4 Property management, acquisition and development 1,711 852 1,714 856 Interest income on note receivable from Preferred Operating Partnership unit holder Property management, acquisition and development 1,213 1,213 Equity in earnings of unconsolidated real estate ventures Rental operations 2,830 2,650 Equity in earnings of unconsolidated real estate ventures - gain on sale of real estate assets and purchase of partners’ interests Property management, acquisition and development 26,923 2,857 Income tax (expense) benefit Rental operations (845 ) (754 ) Tenant reinsurance (2,663 ) (1,874 ) Property management, acquisition and development 743 380 (2,765 ) (2,248 ) Net income (loss) Rental operations 69,210 54,124 Tenant reinsurance 13,584 11,712 Property management, acquisition and development 6,613 (7,200 ) $ 89,407 $ 58,636 Depreciation and amortization expense Rental operations $ 40,586 $ 28,265 Property management, acquisition and development 2,311 2,163 $ 42,897 $ 30,428 Statement of Cash Flows Acquisition of real estate assets Property management, acquisition and development $ (234,820 ) $ (77,082 ) Development and redevelopment of real estate assets Property management, acquisition and development $ (6,543 ) $ (3,140 )

Organization - Additional Infor

Organization - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2016StoreSegments
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of operating storage facilities in which the entity has equity interests (in stores)	1,018
Number of stores owned by franchisees and third parties	353
Number of operating stores owned and/or managed	1,371
Number of states in which operating storage facilities are located	37
Number of reportable segments | Segments	3
Rental Revenue [Member] | Customer Concentration Risk [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Maximum percentage of rental income accounted for by any single tenant	5.00%

Fair Value Disclosures - Schedu

Fair Value Disclosures - Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) - Recurring Basis [Member] $ in Thousands	Mar. 31, 2016USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets - Cash Flow Hedge Swap Agreements	$ 463
Other liabilities - Cash Flow Hedge Swap Agreements	(34,708)
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets - Cash Flow Hedge Swap Agreements	463
Other liabilities - Cash Flow Hedge Swap Agreements	$ (34,708)

Fair Value Disclosures - Additi

Fair Value Disclosures - Additional Information (Detail)	Mar. 31, 2016Store
Debt Instrument Fair Value Carrying Value [Abstract]
Number of stores classified as held for sale	8

Fair Value Disclosures - Sche34

Fair Value Disclosures - Schedule of Fair Value of Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Fair Value of Financial Instruments [Line Items]
Notes receivable from Preferred Operating Partnership unit holders	$ 120,230	$ 120,230
Fixed rate notes payable and notes payable to trusts	2,842,076	2,758,567
Exchangeable senior notes	606,887	623,863
Carrying Value [Member]
Fair Value of Financial Instruments [Line Items]
Notes receivable from Preferred Operating Partnership unit holders	120,230	120,230
Fixed rate notes receivable	84,331	84,331
Fixed rate notes payable and notes payable to trusts	2,271,925	1,806,904
Exchangeable senior notes	640,725	660,364
Fair Value [Member]
Fair Value of Financial Instruments [Line Items]
Notes receivable from Preferred Operating Partnership unit holders	130,856	128,216
Fixed rate notes receivable	85,927	86,814
Fixed rate notes payable and notes payable to trusts	2,329,420	1,828,486
Exchangeable senior notes	$ 767,992	$ 770,523

Earnings Per Common Share - Add

Earnings Per Common Share - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Feb. 29, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 21, 2013
Earnings Per Common Share [Line Items]
Average share price	$ 86.91
Principal amount of notes outstanding	$ 606,887,000			$ 623,863,000
Average closing price of common stock	$ 93.46
Anti-dilutive securities excluded from computation of earnings per common share	875,480	875,480
Operating Partnership [Member] | 2.375% Exchangeable Senior Notes due 2033 (the 2013 Notes) [Member]
Earnings Per Common Share [Line Items]
Principal amount of notes outstanding	$ 65,725,000		$ 19,639,000	85,364,000
Interest rate	2.375%					2.375%
Exchange price	$ 54.87
Principal amount of notes issued						$ 250,000,000
Shares related to the Notes included in the computation for diluted earnings per share	441,598	682,502
Operating Partnership [Member] | Exchangeable Senior Notes 3.125% due 2035 (the 2015 Notes) [Member]
Earnings Per Common Share [Line Items]
Principal amount of notes outstanding	$ 575,000,000			$ 575,000,000
Interest rate	3.125%				3.125%
Exchange price	$ 95.40
Principal amount of notes issued	$ 575,000,000				$ 575,000,000
Shares related to the Notes included in the computation for diluted earnings per share	0	0
Series A Units [Member]
Earnings Per Common Share [Line Items]
Exchangeable preferred operating partnership units settled in cash, minimum	$ 115,000,000
Series B Units [Member]
Earnings Per Common Share [Line Items]
Units outstanding	$ 41,902,000
Anti-dilutive securities excluded from computation of earnings per common share	448,342
Series C Units [Member]
Earnings Per Common Share [Line Items]
Units outstanding	$ 29,639,000
Anti-dilutive securities excluded from computation of earnings per common share	317,130
Series D Units [Member]
Earnings Per Common Share [Line Items]
Units outstanding	$ 13,710,000
Anti-dilutive securities excluded from computation of earnings per common share	146,694
Stock Options [Member]
Earnings Per Common Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per common share	67,812	19,762

Earnings Per Common Share - Sch

Earnings Per Common Share - Schedule of Antidilutive Shares Excluded from Computation of Earnings Per Share (Detail) - shares	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of Units	2,928,493	2,928,493
Equivalent Shares (if converted)	980,912	1,299,756
Series B Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of Units	1,676,087	1,676,087
Equivalent Shares (if converted)	482,133	638,850
Series C Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of Units	704,016	704,016
Equivalent Shares (if converted)	341,032	451,884
Series D Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of Units	548,390	548,390
Equivalent Shares (if converted)	157,747	209,022

Earnings Per Common Share - S37

Earnings Per Common Share - Schedule of Computation of Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Earnings Per Share [Abstract]
Net income attributable to common stockholders	$ 82,592	$ 53,742
Earnings and dividends allocated to participating securities	(165)	(119)
Earnings for basic computations	82,427	53,623
Earnings and dividends allocated to participating securities		119
Income allocated to noncontrolling interest - Preferred Operating Partnership (Series A Units) and Operating Partnership	5,474	3,635
Fixed component of income allocated to noncontrolling interest - Preferred Operating Partnership (Series A Units)	(1,271)	(1,274)
Net income for diluted computations	$ 86,630	$ 56,103
Weighted average common shares outstanding:
Average number of common shares outstanding - basic	124,754,174	116,117,615
Series A Units	875,480	875,480
OP Units	5,621,470	4,365,879
Unvested restricted stock awards included for treasury stock method		282,903
Shares related to exchangeable senior notes and dilutive stock options	704,970	953,841
Average number of common shares outstanding - diluted	131,956,094	122,595,718
Earnings per common share
Basic	$ 0.66	$ 0.46
Diluted	$ 0.66	$ 0.46

Store Acquisitions - Schedule o

Store Acquisitions - Schedule of Operating Properties Acquired (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2016USD ($)Property
Property Acquisitions [Line Items]
Number of Stores | Property	23
Total Consideration Paid	$ 225,537
Cash Consideration Paid	225,156
Net Liabilities/ (Assets) Assumed	381
Fair Value Real estate assets	$ 269,721
New Mexico 1 Property Acquired 3/29/2016 [Member]
Property Acquisitions [Line Items]
Number of Stores | Property	1
Total Consideration Paid	$ 10,958
Cash Consideration Paid	10,928
Net Liabilities/ (Assets) Assumed	30
Fair Value Real estate assets	$ 10,958
New Mexico 1 Property Acquired 3/29/2016 [Member]
Property Acquisitions [Line Items]
Number of Stores | Property	1
Total Consideration Paid	$ 17,940
Cash Consideration Paid	17,905
Net Liabilities/ (Assets) Assumed	35
Fair Value Real estate assets	$ 17,940
Georgia 3 Property Acquired 3/29/2016 [Member]
Property Acquisitions [Line Items]
Number of Stores | Property	3
Total Consideration Paid	$ 25,087
Cash Consideration Paid	25,069
Net Liabilities/ (Assets) Assumed	18
Fair Value Real estate assets	$ 25,087
Texas 1 Property Acquired 3/21/2016 [Member]
Property Acquisitions [Line Items]
Number of Stores | Property	1
Total Consideration Paid	$ 9,994
Cash Consideration Paid	9,969
Net Liabilities/ (Assets) Assumed	25
Fair Value Real estate assets	$ 9,994
Illinois 1 Property Acquired 2/25/2016 [Member]
Property Acquisitions [Line Items]
Number of Stores | Property	1
Total Consideration Paid	$ 16,721
Cash Consideration Paid	16,738
Net Liabilities/ (Assets) Assumed	(17)
Fair Value Real estate assets	$ 16,721
Massachusetts 1 Property Acquired 2/16/2016 [Member]
Property Acquisitions [Line Items]
Number of Stores | Property	1
Total Consideration Paid	$ 16,169
Cash Consideration Paid	16,174
Net Liabilities/ (Assets) Assumed	(5)
Fair Value Real estate assets	$ 16,169
Florida Maryland Nevada New York Tennessee 6 Property Acquired 2/2/2016 [Member]
Property Acquisitions [Line Items]
Number of Stores | Property	6
Total Consideration Paid	$ 53,898
Cash Consideration Paid	53,940
Net Liabilities/ (Assets) Assumed	(42)
Fair Value Real estate assets	$ 98,082
Texas 3 Property Acquired 1/14/2016 [Member]
Property Acquisitions [Line Items]
Number of Stores | Property	3
Total Consideration Paid	$ 22,625
Cash Consideration Paid	22,523
Net Liabilities/ (Assets) Assumed	102
Fair Value Real estate assets	$ 22,625
Florida 1 Property Acquired 1/12/2016 [Member]
Property Acquisitions [Line Items]
Number of Stores | Property	1
Total Consideration Paid	$ 9,001
Cash Consideration Paid	8,980
Net Liabilities/ (Assets) Assumed	21
Fair Value Real estate assets	$ 9,001
Texas 3 Property Acquired 1/7/2016 [Member]
Property Acquisitions [Line Items]
Number of Stores | Property	3
Total Consideration Paid	$ 27,537
Cash Consideration Paid	27,435
Net Liabilities/ (Assets) Assumed	102
Fair Value Real estate assets	$ 27,537
New Mexico 2 Property Acquired 1/7/2016 [Member]
Property Acquisitions [Line Items]
Number of Stores | Property	2
Total Consideration Paid	$ 15,607
Cash Consideration Paid	15,495
Net Liabilities/ (Assets) Assumed	112
Fair Value Real estate assets	$ 15,607

Store Acquisitions - Schedule39

Store Acquisitions - Schedule of Operating Properties Acquired (Parenthetical) (Detail) $ in Thousands	Feb. 02, 2016USD ($)Store
VRS Self Storage LLC Joint Venture [Member]
Property Acquisitions [Line Items]
Number of stores acquired | Store	6
Ownership percentage in joint venture	45.04%
Extra Space Properties 122 LLC [Member]
Property Acquisitions [Line Items]
Number of stores acquired | Store	6
Number of stores transferred to new wholly-owned subsidiary | Store	6
Net carrying amount of properties distributed for spinoff	$ 17,261
Ownership interest percentage, after acquisition	100.00%
Business acquisition, cost of acquired entity, purchase price	$ 44,184
Equity interest fair value remeasurement gain	$ 26,923
Prudential Real Estate and Affiliates [Member] | VRS Self Storage LLC Joint Venture [Member]
Property Acquisitions [Line Items]
Business acquisition, percentage of voting interests acquired	54.96%
Prudential Real Estate and Affiliates [Member] | Extra Space Properties 122 LLC [Member]
Property Acquisitions [Line Items]
Business acquisition, percentage of voting interests acquired	54.96%
Total purchase price	$ 53,940

Store Acquisitions - Additional

Store Acquisitions - Additional Information (Detail) - New Jersey And Virginia, 5 Stores Acquired in 2014 [Member] $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016USD ($)	Dec. 31, 2014Store
Property Acquisition And Dispositions [Line Items]
Number of operating stores acquired | Store		5
Increase in payments due to sellers resulting from higher rental income of properties | $	$ 1,544

Investments in Unconsolidated R

Investments in Unconsolidated Real Estate Ventures - Additional Information (Detail) - Baychester Investments LLC [Member] $ in Thousands	3 Months Ended
	Mar. 31, 2016USD ($)Store
Schedule of Equity Method Investments [Line Items]
Number of stores | Store	1
Amount paid for interest | $	$ 4,794
Equity method ownership percentage	44.40%

Variable Interests - Additional

Variable Interests - Additional Information (Detail)	Mar. 31, 2016ItemJointVenture
Variable Interests And Equity Method Investments Disclosure [Abstract]
Number of wholly-owned unconsolidated subsidiaries | Item	3
Number of interests in consolidated VIE joint ventures | JointVenture	0

Variable Interests - Schedule o

Variable Interests - Schedule of Assets and Liabilities and Maximum Exposure to Loss Related to Trusts (Detail) - USD ($)	Mar. 31, 2016	Dec. 31, 2015
Variable Interest Entity [Line Items]
Notes payable to trusts	$ 117,225,000	$ 117,191,000
Operating Partnership [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Notes payable to trusts	117,225,000
Investment Balance	3,590,000
Maximum exposure to loss	116,000,000
Difference	0
Operating Partnership [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Trust I [Member]
Variable Interest Entity [Line Items]
Notes payable to trusts	36,083,000
Investment Balance	1,083,000
Maximum exposure to loss	35,000,000
Difference	0
Operating Partnership [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Trust II [Member]
Variable Interest Entity [Line Items]
Notes payable to trusts	42,269,000
Investment Balance	1,269,000
Maximum exposure to loss	41,000,000
Difference	0
Operating Partnership [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Trust III [Member]
Variable Interest Entity [Line Items]
Notes payable to trusts	41,238,000
Investment Balance	1,238,000
Maximum exposure to loss	40,000,000
Difference	0
Operating Partnership [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Gross [Member]
Variable Interest Entity [Line Items]
Notes payable to trusts	119,590,000
Investment Balance	3,590,000
Maximum exposure to loss	116,000,000
Difference	0
Operating Partnership [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Unamortized Debt Issuance Expense [Member]
Variable Interest Entity [Line Items]
Notes payable to trusts	(2,365,000)
Difference	$ 0

Derivatives - Additional Inform

Derivatives - Additional Information (Detail)	Mar. 31, 2016USD ($)Item
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Estimated amount of unrealized gains or losses expected to be reclassified as interest expense in next fiscal year	$ 16,403,000
Number of derivative financial instruments | Item	29
Combined notional amount	$ 1,850,111,000
Credit risk derivative, fair value of derivatives in a net liability position	34,708,000
Estimated termination value on settlement	$ 37,240,000

Derivatives - Schedule of Balan

Derivatives - Schedule of Balance Sheet Classification and Fair Value of Entity's Derivative Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Other Assets [Member]
Derivative [Line Items]
Other assets - Asset (Liability) Derivatives	$ 463	$ 4,996
Other Liabilities [Member]
Derivative [Line Items]
Other liabilities - Asset (Liability) Derivatives	$ (34,708)	$ (6,991)

Derivatives - Interest Payments

Derivatives - Interest Payments Recognized as Increase or Decrease in Interest Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Interest Rate Swap [Member]
Derivative [Line Items]
Swap agreements increase (decrease) in interest expenses due to interest payments	$ (4,454)	$ (2,297)

Derivatives - Schedule of Infor

Derivatives - Schedule of Information Relating to Gain (Loss) Recognized on Swap Agreements (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Swap agreements gain (loss) recognized in OCI	$ (34,960)	$ (8,875)
Swap agreements gain (loss) reclassified from OCI - Interest expense	$ (4,454)	$ (2,297)

Exchangeable Senior Notes - Add

Exchangeable Senior Notes - Additional Information (Detail) shares in Thousands	Feb. 29, 2016USD ($)	Jun. 21, 2013USD ($)	Feb. 29, 2016USD ($)shares	Sep. 30, 2015USD ($)	Mar. 31, 2016USD ($)d	Dec. 31, 2015USD ($)
Par Value [Member]
Debt Instrument [Line Items]
Shares issued for value of notes in excess of principal amount | shares			130,909
Value of notes in excess of principal amount			$ 11,380,000
2.375% Exchangeable Senior Notes due 2033 (the 2013 Notes) [Member]
Debt Instrument [Line Items]
Notes exchange, threshold percentage					130.00%
Notes exchange, threshold trading days | d					20
Notes exchange, threshold consecutive trading days					30 days
Effective interest rate on the liability component					4.00%
2.375% Exchangeable Senior Notes due 2033 (the 2013 Notes) [Member] | Operating Partnership [Member]
Debt Instrument [Line Items]
Principal amount of notes issued		$ 250,000,000
Interest rate		2.375%			2.375%
Issuance cost	$ 36,000	$ 1,672,000
Conversion ratio, number of shares per $1,000 principal amount, numerator					18.22
Principal amount used for debt instrument conversion ratio					$ 1,000
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%
Discount rate (as a percent)		1.50%
Amortization period		5 years
Unamortized cash discount	716,000	$ 3,750,000	716,000		$ 438,000	$ 633,000
Principal amount repurchased	$ 19,639,000		$ 19,639,000
Exchangeable Senior Notes 3.125% due 2035 (the 2015 Notes) [Member]
Debt Instrument [Line Items]
Effective interest rate on the liability component					4.00%
Exchangeable Senior Notes 3.125% due 2035 (the 2015 Notes) [Member] | Operating Partnership [Member]
Debt Instrument [Line Items]
Principal amount of notes issued				$ 575,000,000	$ 575,000,000
Interest rate				3.125%	3.125%
Issuance cost				$ 11,992,000
Underwriting fee percentage				2.00%
Amortization period				5 years
Conversion ratio, number of shares per $1,000 principal amount, numerator					10.48
Principal amount used for debt instrument conversion ratio					$ 1,000
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%
Minimum [Member] | 2.375% Exchangeable Senior Notes due 2033 (the 2013 Notes) [Member] | Operating Partnership [Member]
Debt Instrument [Line Items]
Number of days of written notice to holders of notes required for redemption		30 days
Minimum [Member] | Exchangeable Senior Notes 3.125% due 2035 (the 2015 Notes) [Member] | Operating Partnership [Member]
Debt Instrument [Line Items]
Number of days of written notice to holders of notes required for redemption				30 days
Maximum [Member] | 2.375% Exchangeable Senior Notes due 2033 (the 2013 Notes) [Member] | Operating Partnership [Member]
Debt Instrument [Line Items]
Number of days of written notice to holders of notes required for redemption		60 days
Maximum [Member] | Exchangeable Senior Notes 3.125% due 2035 (the 2015 Notes) [Member] | Operating Partnership [Member]
Debt Instrument [Line Items]
Number of days of written notice to holders of notes required for redemption				60 days

Exchangeable Senior Notes - Sch

Exchangeable Senior Notes - Schedule of Information about Total Carrying Amounts of Equity Components, Principal Amounts of Liability Components, Unamortized Discounts and Net Carrying Amounts for Notes (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Feb. 29, 2016	Dec. 31, 2015	Jun. 21, 2013
Debt Instrument [Line Items]
Principal amount of liability components	$ 606,887		$ 623,863
Operating Partnership [Member]
Debt Instrument [Line Items]
Carrying amount of equity components	22,597		22,597
Net carrying amount of liability components	606,887		623,863
Operating Partnership [Member] | 2.375% Exchangeable Senior Notes due 2033 (the 2013 Notes) [Member]
Debt Instrument [Line Items]
Principal amount of liability components	65,725	$ 19,639	85,364
Unamortized discount - equity components	(1,827)		(2,605)
Unamortized cash discount	(438)	$ (716)	(633)	$ (3,750)
Operating Partnership [Member] | Exchangeable Senior Notes 3.125% due 2035 (the 2015 Notes) [Member]
Debt Instrument [Line Items]
Carrying amount of equity components	22,597		22,597
Principal amount of liability components	575,000		575,000
Unamortized discount - equity components	(20,533)		(21,565)
Operating Partnership [Member] | Exchangeable Senior Notes [Member]
Debt Instrument [Line Items]
Unamortized debt issuance costs	$ (11,040)		$ (11,698)

Exchangeable Senior Notes - Sum

Exchangeable Senior Notes - Summary of Amount of Interest Cost Recognized Relating to Contractual Interest Rates and Amortization of Discounts on Liability Components of Notes (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Debt Disclosure [Abstract]
Contractual interest	$ 4,882	$ 1,484
Amortization of discount	1,233	697
Total interest expense recognized	$ 6,115	$ 2,181

Exchangeable Senior Notes - S51

Exchangeable Senior Notes - Summary of Repurchase of Debt (Detail) - USD ($) $ in Thousands	Feb. 29, 2016	Jun. 21, 2013	Mar. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Exchangeable senior notes repurchased			$ 606,887	$ 623,863
Operating Partnership [Member] | 2.375% Exchangeable Senior Notes due 2033 (the 2013 Notes) [Member]
Debt Instrument [Line Items]
Principal amount repurchased	$ 19,639
Extinguishment of liability component	18,887
Reacquisition of equity component	12,132
Total consideration paid for repurchase	31,019
Exchangeable senior notes repurchased	19,639		65,725	85,364
Extinguishment of liability component	(18,887)
Discount on exchangeable senior notes	(716)	$ (3,750)	$ (438)	$ (633)
Related debt issuance costs	(36)	$ (1,672)
Gain/(loss) on repurchase	$ 0

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) $ / shares in Units, $ in Thousands	Aug. 28, 2015USD ($)SalesAgents	Mar. 31, 2016USD ($)$ / sharesshares
Changes In Equity And Comprehensive Income Line Items [Line Items]
Proceeds from issuance of common stock		$ 73,574
At the Market Equity Distribution Agreement [Member]
Changes In Equity And Comprehensive Income Line Items [Line Items]
Number of sales agents | SalesAgents	5
Aggregate offering price of common share	$ 400,000
Common stock issued and sold | shares		831,300
Average price per share | $ / shares		$ 89.66
Proceeds from issuance of common stock		$ 73,574

Noncontrolling Interest Represe

Noncontrolling Interest Represented by Preferred Operating Partnership Units - Series A Participating Redeemable Preferred Units - Additional Information (Detail) $ in Thousands	Oct. 03, 2014USD ($)shares	Jun. 25, 2007USD ($)shares	Jun. 15, 2007Propertyshares	Mar. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Noncontrolling Interest in Operating Partnership [Line Items]
Loan to holders of preferred OP units | $				$ 120,230	$ 120,230
Operating Partnership [Member] | Series A Participating Redeemable Preferred Units [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Number of stores acquired | Property			10
Operating Partnership [Member] | Series A Participating Redeemable Preferred Units [Member] | Series A Units [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Preferred units issued as part of acquisition (in units) | shares			989,980
Fixed priority return on preferred OP units, stated return rate (as a percent)				5.00%
Fixed priority return on preferred OP units, amount | $				$ 115,000
Fixed priority return on preferred OP units, liquidation value | $				$ 115,000
Operating Partnership Holders of A Units [Member] | Series A Participating Redeemable Preferred Units [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Loan to holders of preferred OP units | $		$ 100,000
Note receivable interest rate (as a percent)		4.85%
Maximum number of preferred OP units converted prior to the maturity date of the loan (in shares) | shares		114,500
A units redeemed | shares	114,500
A units redeemed ,value | $	$ 4,794
Additional units redeemed | shares	0
Common shares issued in Preferred Unit redemption | shares	280,331

Noncontrolling Interest Repre54

Noncontrolling Interest Represented by Preferred Operating Partnership Units - Series B Redeemable Preferred Units - Additional Information (Detail) - Series B Redeemable Preferred Units [Member] $ / shares in Units, $ in Thousands	Apr. 03, 2014USD ($)Storeshares	Sep. 26, 2013USD ($)Storeshares	Aug. 29, 2013Store	Mar. 31, 2016USD ($)$ / shares
Series B Units [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Liquidation value (in dollars per share) | $ / shares				$ 25
Fixed liquidation value				$ 41,902
Annual rate of return (as a percent)				6.00%
Georgia, 1 Property Acquired 4/3/2014 [Member] | Series B Units [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Preferred units issued as part of acquisition (in units) | shares	333,360
Preferred units issued as part of acquisition	$ 8,334
Georgia, 1 Property Acquired 4/3/2014 [Member] | Operating Partnership [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Cash portion of payment for acquisition	$ 15,158
Number of stores acquired | Store	1
California, 20 Properties Acquired 2013-September [Member] | Operating Partnership [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Cash portion of payment for acquisition		$ 100,876
Number of stores acquired | Store		1	19
Number of stores acquired as part of portfolio acquisition | Store			20
Debt assumed		$ 98,960
Number of common units issued as part of acquisition | shares		1,448,108
OP units issued as part of the acquisition		$ 62,341
California, 20 Properties Acquired 2013-September [Member] | Operating Partnership [Member] | Series B Units [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Preferred units issued as part of acquisition (in units) | shares		1,342,727
Preferred units issued as part of acquisition		$ 33,568

Noncontrolling Interest Repre55

Noncontrolling Interest Represented by Preferred Operating Partnership Units - Series C Convertible Redeemable Preferred Units - Additional Information (Detail) $ / shares in Units, $ in Thousands	Nov. 19, 2013Store	Dec. 31, 2014USD ($)	Mar. 31, 2016USD ($)shares$ / shares	May. 31, 2014USD ($)Storeshares	Dec. 31, 2015USD ($)
Noncontrolling Interest in Operating Partnership [Line Items]
Loan to holders of preferred OP units			$ 120,230		$ 120,230
Series C Convertible Redeemable Preferred Units [Member] | Series C Units [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Liquidation value (in dollars per share) | $ / shares			$ 42.10
Fixed liquidation value			$ 29,639
Quarterly distribution per preferred OP unit payable above quarterly distribution for common OP Unit | $ / shares			$ 0.18
Number of quarters immediately preceding the fifth anniversary of issuance for which distribution is payable			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 | shares			0.9145
Loan to holders of preferred OP units		$ 20,230
Note receivable interest rate (as a percent)		5.00%
Note receivable maturity date		Dec. 15, 2024
California, Properties Acquired December 2013 [Member] | Series C Convertible Redeemable Preferred Units [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Number of stores acquired | Store	12
Ownership interests in five stores through joint ventures prior to the acquisition				35.00%
Ownership interest in one store through joint ventures prior to the acquisition				40.00%
Number of stores in which ownership interest was held prior to acquisition | Store				1
Number of stores in which ownership interest was held prior to acquisition of remaining properties | Store				5
California, Properties Acquired December 2013 [Member] | Series C Convertible Redeemable Preferred Units [Member] | Operating Partnership [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Number of stores acquired | Store				6
Cash portion of payment for acquisition				$ 45,722
Debt assumed				$ 37,532
California, Properties Acquired December 2013 [Member] | Series C Convertible Redeemable Preferred Units [Member] | Series C Units [Member] | Operating Partnership [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Preferred units issued as part of acquisition (in units) | shares				704,016
Preferred units issued as part of acquisition				$ 30,960

Noncontrolling Interest Repre56

Noncontrolling Interest Represented by Preferred Operating Partnership Units - Series D Redeemable Preferred Units - Additional Information (Detail) - Series D Redeemable Preferred Units [Member] - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended
	Dec. 31, 2014	Mar. 31, 2016
Series D Units [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Liquidation value (in dollars per share)		$ 25
Fixed liquidation value		$ 13,710
Annual rate of return (as a percent)		5.00%
Self Storage Facility in Florida [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Cash portion of payment for acquisition	$ 5,621
Self Storage Facility in Florida [Member] | Series D Units [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Preferred units issued as part of acquisition (in units)	548,390
Preferred units issued as part of acquisition	$ 13,710

Noncontrolling Interest in Oper

Noncontrolling Interest in Operating Partnership - Additional Information (Detail) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2016USD ($)$ / sharesshares
Noncontrolling Interest in Operating Partnership [Line Items]
Period used as a denomination to determine the average closing price of common stock	10 days
OP units conversion basis	One-for-one basis
Ten day average closing stock price | $ / shares	$ 90.76
Consideration to be paid on redemption of common OP units | $	$ 510,191
Operating Partnership [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Ownership interest held by entity (as a percent)	93.00%
Noncontrolling interest in operating partnership (as a percent)	7.00%
OP units outstanding | shares	5,621,322

Other Noncontrolling Interests

Other Noncontrolling Interests - Additional Information (Detail)	Jun. 11, 2015USD ($)Property	Mar. 31, 2016JointVenture
Noncontrolling Interest in Operating Partnership [Line Items]
Purchase of capital interest by entity in a joint venture partner of a consolidated property	1.00%
Cash paid for acquiring interest in a joint venture partner of a consolidated property	$ 1,267,000
Number of operating stores owned by consolidated joint venture | Property	19
Carrying amount of noncontrolling interest	$ 0
Other [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Number of consolidated joint ventures | JointVenture		2
Other [Member] | Minimum [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Voting interests of third-party owners		17.50%
Other [Member] | Maximum [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Voting interests of third-party owners		20.00%

Equity in Earnings of Unconso59

Equity in Earnings of Unconsolidated Real Estate Ventures - Gain on Sale of Real Estate and Purchase of Joint Venture Partners' Interests - Additional Information (Detail) $ in Thousands	Feb. 02, 2016USD ($)Store	Mar. 31, 2015USD ($)Store
Schedule Of Results Related To Equity Accounted Investees [Line Items]
Ownership interest acquired in joint venture (as a percent)		82.40%
Cash paid for acquiring equity interest in the joint venture		$ 1,700
Company held mortgage notes receivable eliminated as a result of the acquisition		$ 11,009
Equity ownership prior to the acquisition (as a percent)		17.60%
Non-cash gain		$ 1,629
VRS Self Storage LLC Joint Venture [Member]
Schedule Of Results Related To Equity Accounted Investees [Line Items]
Number of stores acquired | Store	6
ESS PRISA II LLC [Member]
Schedule Of Results Related To Equity Accounted Investees [Line Items]
Ownership interest percentage		2.00%
Gain (loss) on sale of property		$ 60,496
Percentage of gain from sale of property		2.00%
Gain (loss) from sale of property		$ 1,228
ESS PRISA II LLC [Member] | New York [Member]
Schedule Of Results Related To Equity Accounted Investees [Line Items]
Number of operating stores sold by consolidated joint venture | Store		1
Proceeds from sale of property		$ 90,000
VRS Self Storage LLC Joint Venture [Member]
Schedule Of Results Related To Equity Accounted Investees [Line Items]
Equity interest fair value remeasurement non-cash gain	$ 26,923

Segment Information - Additiona

Segment Information - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2016Segments
Segment Reporting [Abstract]
Number of reportable segments	3

Segment Information - Schedule

Segment Information - Schedule of Financial Information of Business Segments (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Segment Reporting Information [Line Items]
Investment in unconsolidated real estate ventures	$ 89,224		$ 103,007
Total assets	6,291,419		6,071,407
Total revenues	229,403	$ 173,154
Operating expenses, including depreciation and amortization	135,775	97,718
Income (loss) from operations	93,628	75,436
Loss on earnout from prior acquisition	(1,544)
Interest income	1,714	856
Interest expense	(31,359)	(21,431)
Non-cash interest expense related to the amortization of discount on equity component of exchangeable senior notes	(1,233)	(697)
Interest income on note receivable from Preferred Operating Partnership unit holder	1,213	1,213
Equity in earnings of unconsolidated real estate ventures	2,830	2,650
Equity in earnings of unconsolidated real estate ventures - gain on sale of real estate assets and purchase of partners' interests	26,923	2,857
Income tax (expense) benefit	2,765	2,248
Net income (loss)	89,407	58,636
Depreciation and amortization expense	42,897	30,428
Acquisition of real estate assets	(234,820)	(77,082)
Development and redevelopment of real estate assets	(6,543)	(3,140)
Rental Operations [Member]
Segment Reporting Information [Line Items]
Investment in unconsolidated real estate ventures	89,224		103,007
Total assets	5,901,210		5,674,030
Total revenues	199,488	148,894
Operating expenses, including depreciation and amortization	101,698	75,509
Income (loss) from operations	97,790	73,385
Interest expense	(30,565)	(21,157)
Equity in earnings of unconsolidated real estate ventures	2,830	2,650
Income tax (expense) benefit	845	754
Net income (loss)	69,210	54,124
Depreciation and amortization expense	40,586	28,265
Tenant Reinsurance [Member]
Segment Reporting Information [Line Items]
Total assets	34,180		37,696
Total revenues	20,555	16,510
Operating expenses, including depreciation and amortization	4,311	2,928
Income (loss) from operations	16,244	13,582
Interest income	3	4
Income tax (expense) benefit	2,663	1,874
Net income (loss)	13,584	11,712
Property Management Acquisition and Development [Member]
Segment Reporting Information [Line Items]
Total assets	356,029		$ 359,681
Total revenues	9,360	7,750
Operating expenses, including depreciation and amortization	29,766	19,281
Income (loss) from operations	(20,406)	(11,531)
Loss on earnout from prior acquisition	(1,544)
Interest income	1,711	852
Interest expense	(794)	(274)
Non-cash interest expense related to the amortization of discount on equity component of exchangeable senior notes	(1,233)	(697)
Interest income on note receivable from Preferred Operating Partnership unit holder	1,213	1,213
Equity in earnings of unconsolidated real estate ventures - gain on sale of real estate assets and purchase of partners' interests	26,923	2,857
Income tax (expense) benefit	743	380
Net income (loss)	6,613	(7,200)
Depreciation and amortization expense	2,311	2,163
Acquisition of real estate assets	(234,820)	(77,082)
Development and redevelopment of real estate assets	$ (6,543)	$ (3,140)

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Thousands	Mar. 31, 2016USD ($)Store
Commitments And Contingencies [Line Items]
Litigation liability recorded | $	$ 4,000
Contract Amount [Member]
Commitments And Contingencies [Line Items]
Number of stores to be acquired	21
Purchase price | $	$ 349,376
Number of stores scheduled to be closed	26
Contract Amount [Member] | Joint Venture Partners [Member]
Commitments And Contingencies [Line Items]
Number of stores to be acquired	10
Purchase price | $	$ 302,800
Number of stores scheduled to be closed	7
Number of stores expected to be closed	3
Contract Amount [Member] | Construction [Member]
Commitments And Contingencies [Line Items]
Number of stores to be acquired	9

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) $ in Thousands	Apr. 20, 2016USD ($)Store	Apr. 01, 2016USD ($)Store	Mar. 31, 2016USD ($)
Subsequent Event [Line Items]
Cash portion of payment for acquisition			$ 225,537
Subsequent Event [Member]
Subsequent Event [Line Items]
Number of operating stores acquired | Store		10
Cash portion of payment for acquisition		$ 88,048
Number of stores sold | Store	7
Proceeds from sale of real estate	$ 18,000