Extra Space Storage (EXR) 10-Q 6 Nov 15 2015 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2015	Oct. 30, 2015
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q3
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		123,456,914

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Assets:
Real estate assets, net	$ 4,452,251	$ 4,139,626
Investments in unconsolidated real estate ventures	84,671	85,711
Cash and cash equivalents	1,115,532	47,663
Restricted cash	228,629	25,245
Receivables from related parties and affiliated real estate joint ventures	3,016	11,778
Other assets, net	118,737	92,084
Total assets	6,002,836	4,402,107
Liabilities, Noncontrolling Interests and Equity:
Notes payable	2,527,756	1,872,067
Premium on notes payable	1,235	3,281
Exchangeable senior notes	660,364	250,000
Discount on exchangeable senior notes	(26,146)	(13,054)
Notes payable to trusts	119,590	119,590
Lines of credit	185,000	138,000
Accounts payable and accrued expenses	76,303	65,521
Other liabilities	71,394	54,719
Total liabilities	$ 3,615,496	$ 2,490,124
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, 123,332,292 and 116,360,239 shares issued and outstanding at September 30, 2015 and December 31, 2014, respectively	$ 1,233	$ 1,163
Additional paid-in capital	2,401,886	1,995,484
Accumulated other comprehensive loss	(20,812)	(1,484)
Accumulated deficit	(273,015)	(257,738)
Total Extra Space Storage Inc. stockholders' equity	2,109,292	1,737,425
Noncontrolling interest represented by Preferred Operating Partnership units, net of $120,230 notes receivable	80,869	81,152
Noncontrolling interests in Operating Partnership	197,017	92,422
Other noncontrolling interests	162	984
Total noncontrolling interests and equity	2,387,340	1,911,983
Total liabilities, noncontrolling interests and equity	$ 6,002,836	$ 4,402,107

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
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	123,332,292	116,360,239
Common stock, shares outstanding	123,332,292	116,360,239
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		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Revenues:
Property rental	$ 170,548	$ 144,669	$ 480,466	$ 415,448
Tenant reinsurance	18,226	15,385	52,076	43,356
Management fees and other income	8,723	9,013	23,969	23,167
Total revenues	197,497	169,067	556,511	481,971
Expenses:
Property operations	48,878	43,294	144,331	129,070
Tenant reinsurance	3,608	2,930	9,819	8,133
Acquisition related costs	280	436	5,703	3,885
General and administrative	16,716	15,665	49,620	46,436
Depreciation and amortization	30,711	29,249	92,691	85,895
Total expenses	100,193	91,574	302,164	273,419
Income from operations	97,304	77,493	254,347	208,552
Gain (loss) on real estate transactions and earnout from prior acquisitions	1,101	(2,500)	1,501	(10,285)
Interest expense	(20,811)	(20,681)	(65,053)	(60,937)
Non-cash interest expense related to amortization of discount on equity component of exchangeable senior notes	(805)	(679)	(2,198)	(2,004)
Interest income	356	186	1,640	1,167
Interest income on note receivable from Preferred Operating Partnership unit holder	1,213	1,213	3,638	3,638
Income before equity in earnings of unconsolidated real estate ventures and income tax expense	78,358	55,032	193,875	140,131
Equity in earnings of unconsolidated real estate ventures	3,403	2,777	9,054	7,800
Equity in earnings of unconsolidated real estate ventures-gain on sale of real estate assets and purchase of joint venture partners' interests		378	2,857	3,816
Income tax (expense) benefit	(3,561)	1,006	(7,994)	(5,337)
Net income	78,200	59,193	197,792	146,410
Net income allocated to Preferred Operating Partnership noncontrolling interests	(3,112)	(2,977)	(9,045)	(8,281)
Net income allocated to Operating Partnership and other noncontrolling interests	(3,370)	(1,988)	(7,948)	(4,896)
Net income attributable to common stockholders	$ 71,718	$ 54,228	$ 180,799	$ 133,233
Earnings per common share
Basic	$ 0.58	$ 0.47	$ 1.52	$ 1.15
Diluted	$ 0.58	$ 0.47	$ 1.51	$ 1.15
Weighted average number of shares
Basic	122,644,837	115,726,911	118,564,872	115,606,845
Diluted	130,398,111	121,617,554	125,406,313	121,551,889
Cash dividends paid per common share	$ 0.59	$ 0.47	$ 1.65	$ 1.34

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 78,200	$ 59,193	$ 197,792	$ 146,410
Other comprehensive income (loss):
Change in fair value of interest rate swaps	(20,019)	1,834	(20,307)	(6,614)
Total comprehensive income	58,181	61,027	177,485	139,796
Less: comprehensive income attributable to noncontrolling interests	5,456	5,137	16,014	12,984
Comprehensive income attributable to common stockholders	$ 52,725	$ 55,890	$ 161,471	$ 126,812

Condensed Consolidated Stateme6

Condensed Consolidated Statement of Noncontrolling Interests and Equity - 9 months ended Sep. 30, 2015 - 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, 2014	$ 1,911,983	$ 14,809	$ 41,903	$ 10,730	$ 13,710	$ 92,422	$ 984	$ 1,163	$ 1,995,484	$ (1,484)	$ (257,738)
Balances (in shares) at Dec. 31, 2014	116,360,239							116,360,239
Issuance of common stock upon the exercise of options	$ 1,424							$ 1	1,423
Issuance of common stock upon the exercise of options (in shares)								72,874
Restricted stock grants issued	2							$ 2
Restricted stock grants issued (in shares)								173,354
Restricted stock grants cancelled (in shares)								(16,025)
Issuance of common stock, net of offering costs	446,909							$ 67	446,842
Issuance of common stock, net of offering costs (in shares)								6,735,000
Compensation expense related to stock-based awards	4,385								4,385
Purchase of remaining equity interest in existing consolidated joint venture	(1,268)						(822)		(446)
Issuance of Operating Partnership units in conjunction with acquisition	106,522					106,522
Repurchase of equity portion of 2013 exchangeable senior notes	(70,112)								(70,112)
Issuance of 2015 exchangeable senior notes - equity component	22,597								22,597
Redemption of Operating Partnership units for common stock						(150)			150
Redemption of Operating Partnership units for common stock (in shares)								6,850
Net income	197,792	5,114	1,885	1,532	514	7,948					180,799
Other comprehensive income (loss)	(20,307)	(135)				(844)				(19,328)
Tax effect from vesting of restricted stock grants and stock option exercises	1,563								1,563
Distributions to Operating Partnership units held by noncontrolling interests	(18,074)	(5,261)	(1,886)	(1,532)	(514)	(8,881)
Dividends paid on common stock at $1.65 per share	(196,076)										(196,076)
Balances at Sep. 30, 2015	$ 2,387,340	$ 14,527	$ 41,902	$ 10,730	$ 13,710	$ 197,017	$ 162	$ 1,233	$ 2,401,886	$ (20,812)	$ (273,015)
Balances (in shares) at Sep. 30, 2015	123,332,292							123,332,292

Condensed Consolidated Stateme7

Condensed Consolidated Statement of Noncontrolling Interests and Equity (Parenthetical) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement of Stockholders' Equity [Abstract]
Dividends paid on common stock, per share	$ 0.59	$ 0.47	$ 1.65	$ 1.34

Condensed Consolidated Stateme8

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Cash flows from operating activities:
Net income	$ 197,792	$ 146,410
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	92,691	85,895
Amortization of deferred financing costs	4,876	4,955
Loss (gain) on real estate transactions and earnout from prior acquisitions	(1,501)	2,500
Non-cash interest expense related to amortization of discount on equity component of exchangeable senior notes	2,198	2,004
Non-cash interest expense related to amortization of premium on notes payable	(2,046)	(2,350)
Compensation expense related to stock-based awards	4,385	3,855
Gain on sale of real estate assets and purchase of joint venture partners' interests	(2,857)	(3,438)
Distributions from unconsolidated real estate ventures in excess of earnings	4,020	3,989
Changes in operating assets and liabilities:
Receivables from related parties and affiliated real estate joint ventures	(2,247)	(434)
Other assets	(20,022)	467
Accounts payable and accrued expenses	10,782	12,927
Other liabilities	(1,790)	(216)
Net cash provided by operating activities	286,281	256,564
Cash flows from investing activities:
Acquisition of real estate assets	(263,404)	(328,235)
Development and redevelopment of real estate assets	(15,137)	(11,288)
Proceeds from sale of real estate assets	800
Change in restricted cash	(203,384)	(4,754)
Investment in unconsolidated real estate ventures	(549)
Return of investment in unconsolidated real estate ventures	61
Purchase/issuance of notes receivable		(9,028)
Purchase of equipment and fixtures	(4,821)	(3,636)
Net cash used in investing activities	(486,434)	(356,941)
Cash flows from financing activities:
Proceeds from the sale of common stock, net of offering costs	446,909
Net proceeds from the issuance of 2015 exchangeable senior notes	563,500
Proceeds from notes payable and lines of credit	1,718,753	505,957
Principal payments on notes payable and lines of credit	(1,016,064)	(312,287)
Repurchase of 2013 exchangeable senior notes	(227,212)
Deferred financing costs	(5,138)	(3,851)
Net proceeds from exercise of stock options	1,424	2,717
Dividends paid on common stock	(196,076)	(155,410)
Distributions to noncontrolling interests	(18,074)	(14,256)
Net cash provided by financing activities	1,268,022	22,870
Net increase (decrease) in cash and cash equivalents	1,067,869	(77,507)
Cash and cash equivalents, beginning of the period	47,663	126,723
Cash and cash equivalents, end of the period	1,115,532	49,216
Supplemental schedule of cash flow information
Interest paid	60,040	53,345
Income taxes paid	1,555	3,237
Redemption of Operating Partnership units held by noncontrolling interests for common stock:
Noncontrolling interests in Operating Partnership	(150)
Common stock and paid-in capital	150
Tax effect from vesting of restricted stock grants and option exercises
Other assets	1,563	2,883
Paid-in capital	(1,563)	(2,883)
Acquisitions of real estate assets
Real estate assets, net	122,132	60,465
Notes payable assumed		(38,347)
Operating Partnership units issued	(106,522)	$ (22,118)
Receivables from related parties and affiliated real estate joint ventures	$ (15,610)

Organization

Organization	9 Months Ended
	Sep. 30, 2015
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 (“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 September 30, 2015, the Company had direct and indirect equity interests in 868 stores. In addition, the Company managed 302 stores for third parties, bringing the total number of stores which it owns and/or manages to 1,170. These stores are located in 36 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	9 Months Ended
	Sep. 30, 2015
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 and nine months ended September 30, 2015, are not necessarily indicative of results that may be expected for the year ending December 31, 2015. The condensed consolidated balance sheet as of December 31, 2014 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, 2014, as filed with the Securities and Exchange Commission. Reclassifications Certain amounts in the Company’s 2014 consolidated financial statements and supporting note disclosures have been reclassified to conform to the current period presentation. Such reclassifications did not impact previously reported net income or accumulated deficit. Recently Issued Accounting Standards In April 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-08, “ Presentation of Financial Statements (Topic 205) and Property, Plant and Equipment (Topic 360): Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity. In May 2014, the FASB issued 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 2015-03, “ Interest - Imputation of Interest: Simplifying the Presentation of Debt Issuance Costs, 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,

Fair Value Disclosures

Fair Value Disclosures	9 Months Ended
	Sep. 30, 2015
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 Financial Accounting Standards Board’s fair value measurement guidance, the Company made an accounting policy election to measure the credit risk of its derivative financial instruments that are subject to master netting agreements on a net basis by counterparty portfolio. Although the Company has determined that the majority of the inputs used to value its derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with its derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default by the Company and its counterparties. However, as of September 30, 2015, 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 September 30, 2015, aggregated by the level in the fair value hierarchy within which those measurements fall. Fair Value Measurements at Reporting Date Using Description September 30, Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Other assets - Cash Flow Hedge Swap Agreements $ 142 $ — $ 142 $ — Other liabilities - Cash Flow Hedge Swap Agreements $ (20,403 ) $ — $ (20,403 ) $ — The Company did not have any significant assets or liabilities that are re-measured on a recurring basis using significant unobservable inputs as of September 30, 2015 or December 31, 2014. 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, a valuation allowance is established. The operations of assets held for sale or sold during the period are presented as part of normal operations for all periods presented. The Company assesses 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 September 30, 2015 and December 31, 2014 approximate fair value. The fair values of the Company’s notes receivable from Preferred Operating Partnership unit holders 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: September 30, 2015 December 31, 2014 Fair Carrying Fair Carrying Notes receivable from Preferred Operating Partnership unit holders $ 130,402 $ 120,230 $ 126,380 $ 120,230 Fixed rate notes payable and notes payable to trusts $ 1,963,291 $ 1,834,199 $ 1,320,370 $ 1,283,893 Exchangeable senior notes $ 695,047 $ 660,364 $ 276,095 $ 250,000

Earnings Per Common Share

Earnings Per Common Share	9 Months Ended
	Sep. 30, 2015
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 September 30, 2015 and 2014, options to purchase approximately 82,571 and 29,547 shares of common stock, respectively, and for the nine months ended September 30, 2015 and 2014, options to purchase 50,144 and 27,045 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. For the Three Months Ended September 30, 2015 September 30, 2014 Number of Equivalent (if converted) Number of Equivalent (if converted) Series B Units 1,676,087 572,121 1,676,087 793,602 Series C Units 704,016 404,684 704,016 561,346 Series D Units 548,390 187,189 — — 2,928,493 1,163,994 2,380,103 1,354,948 For the Nine Months Ended September 30, 2015 September 30, 2014 Number of Equivalent (if converted) Number of Equivalent (if converted) Series B Units 1,676,087 607,806 1,563,746 777,364 Series C Units 704,016 429,926 571,973 478,824 Series D Units 548,390 198,865 — — 2,928,493 1,236,597 2,135,719 1,256,188 The Operating Partnership had $85,364 of its 2.375% Exchangeable Senior Notes due 2033 (the “2013 Notes”) issued and outstanding as of September 30, 2015. 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 $55.12 per share as of September 30, 2015, 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 September 30, 2015 (see footnote 8). 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 September 30, 2015, and could change over time as described in the indenture. The Company has irrevocably agreed to pay only cash for the accreted principal amount of the 2015 Notes relative to its exchange obligations, but retained the right to satisfy the exchange obligation in excess of the accreted principal amount in cash and/or common stock. Though the Company has retained that right, Accounting Standards Codification (“ASC”) 260, “Earnings per Share,” 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 September 30, 2015 of $41,903 by the closing price of the Company’s common stock as of September 30, 2015 of $77.16 per share. 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 September 30, 2015 of $29,639 by the closing price of the Company’s common stock as of September 30, 2015 of $77.16 per share. 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 September 30, 2015 of $13,710 by the closing price of the Company’s common stock as of September 30, 2015 of $77.16 per share. The computation of earnings per common share was as follows for the periods presented: For the Three Months For the Nine Months 2015 2014 2015 2014 Net income attributable to common stockholders $ 71,718 $ 54,228 $ 180,799 $ 133,233 Earnings and dividends allocated to participating securities (173 ) (125 ) (432 ) (366 ) Earnings for basic computations 71,545 54,103 180,367 132,867 Earnings and dividends allocated to participating securities 173 125 — 366 Income allocated to noncontrolling interest - Preferred Operating Partnership (Series A Units) and Operating Partnership 5,151 3,875 13,062 10,318 Fixed component of income allocated to noncontrolling interest - Preferred Operating Partnership (Series A Units) (1,272 ) (1,438 ) (3,817 ) (4,313 ) Net income for diluted computations $ 75,597 $ 56,665 $ 189,612 $ 139,238 Weighted average common shares outstanding: Average number of common shares outstanding - basic 122,644,837 115,726,911 118,564,872 115,606,845 Series A Units 875,480 989,980 875,480 989,980 OP Units 5,934,539 4,334,118 5,320,130 4,334,118 Unvested restricted stock awards included for treasury stock method 304,610 294,616 — 321,346 Shares related to 2013 exchangeable senior notes and dilutive stock options 638,645 271,929 645,831 299,600 Average number of common shares outstanding - diluted 130,398,111 121,617,554 125,406,313 121,551,889 Earnings per common share Basic $ 0.58 $ 0.47 $ 1.52 $ 1.15 Diluted $ 0.58 $ 0.47 $ 1.51 $ 1.15

Store Acquisitions

Store Acquisitions	9 Months Ended
	Sep. 30, 2015
Business Combinations [Abstract]
Store Acquisitions	5. STORE ACQUISITIONS The following table summarizes the Company’s acquisitions of operating stores for the nine months ended September 30, 2015, and does not include purchases of raw land or improvements made to existing assets: Consideration Paid Acquisition Date Fair Value Property Location Number Date of Total Cash Paid Non-cash Notes Previous Net Value of Number of Land Building Intangible Closing Maryland 1 9/10/2015 $ 6,165 $ 6,183 $ — $ — $ — $ (18 ) $ — — $ 794 $ 5,178 $ 119 $ 74 North Carolina 1 6/19/2015 6,987 6,926 — — — 61 — — 1,408 5,461 107 11 Florida 1 6/18/2015 17,657 12,677 — — — 207 4,773 71,054 — 17,220 327 110 Florida (3) 1 6/17/2015 6,076 412 1,100 4,601 — (37 ) — — 534 5,364 125 53 Illinois 1 6/8/2015 10,046 9,970 — — — 76 — — 964 9,085 — (3 ) Massachusetts 1 5/13/2015 12,512 12,515 — — — (3 ) — — 1,625 10,875 — 12 Georgia 1 5/7/2015 6,498 6,458 — — — 40 — — 2,087 4,295 114 2 North Carolina 1 5/5/2015 11,007 10,976 — — — 31 — — 4,050 6,867 77 13 Georgia 1 4/24/2015 6,500 6,451 — — — 49 — — 370 6,014 114 2 Arizona, Texas 22 4/15/2015 178,252 75,681 — — — 822 101,749 1,504,277 24,087 151,465 2,121 579 Texas 1 4/14/2015 8,650 8,580 — — — 70 — — 619 7,861 160 10 California (2) 1 3/30/2015 12,699 1,700 1,629 11,009 (1,264 ) (375 ) — — 1,025 11,479 195 — South Carolina 2 3/30/2015 13,165 13,143 — — — 22 — — 1,763 11,229 144 29 Virginia 1 3/17/2015 5,073 5,065 — — — 8 — — 118 4,797 81 77 Texas 1 2/24/2015 13,570 13,519 — — — 51 — — 1,511 11,861 182 16 Texas 3 1/13/2015 41,904 41,806 — — — 98 — — 12,080 29,489 300 35 2015 Totals 40 $ 356,761 $ 232,062 $ 2,729 $ 15,610 $ (1,264 ) $ 1,102 $ 106,522 1,575,331 $ 53,035 $ 298,540 $ 4,166 $ 1,020 (1) This column represents costs paid at closing. The amounts shown exclude other acquisition costs paid before or after the closing date. (2) This represents the acquisition of a joint venture partners’ interest in Extra Space of Sacramento One LLC (“Sacramento One”), an existing joint venture, for $1,700 in cash. The result of the acquisition is that the Company owns 100% of Sacramento One, which owned one store located in California. Prior to the acquisition date, the Company accounted for its interest in Sacramento One as an equity-method investment, and the Company also held mortgage notes receivable from Sacramento One totalling $11,009, including related interest. The total acquisition date fair value of the Company’s previous equity interest was approximately $365 and is included in consideration transfered. The Company recognized a non-cash gain of $1,629 as a result of remeasuring the fair value of its equity interest held prior to the acquisition. The store is consolidated subsequent to the acquisition as the Company owns 100% of the store. (3) The Company determined the consideration paid for this store was below its market value, and recognized a $1,100 gain, representing the difference bewteen the fair value of the store and the consideration paid.

Variable Interests

Variable Interests	9 Months Ended
	Sep. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Variable Interests	6. 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 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 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 September 30, 2015: 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 $ — The Company had no consolidated VIEs during the nine months ended September 30, 2015.

Derivatives

Derivatives	9 Months Ended
	Sep. 30, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives	7. 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 and nine months ended September 30, 2015 and 2014, such derivatives were used to hedge the variable cash flows associated with existing variable-rate debt. The Company held 28 derivative financial instruments which had a total combined notional amount of $1,110,145 as of September 30, 2015. 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 September 30, 2015 December 31, 2014 Derivatives designated as hedging instruments: Fair Value Other assets $ 142 $ 3,583 Other liabilities $ (20,403 ) $ (3,533 ) 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 For the Three Months Ended September 30, Type Income (Expense) 2015 2014 Swap Agreements Interest expense $ (3,084 ) $ (2,172 ) Classification of For the Nine Months Ended September 30, Type Income (Expense) 2015 2014 Swap Agreements Interest expense $ (8,017 ) $ (6,782 ) Gain (loss) recognized in OCI Location of amounts Gain (loss) reclassifed from OCI For the Three Months Ended September 30, reclassified from OCI For the Three Months Ended September 30, Type 2015 2014 into income 2015 2014 Swap Agreements $ (23,073 ) $ 1,824 Interest expense $ (3,084 ) $ (2,172 ) Gain (loss) recognized in OCI Location of amounts Gain (loss) reclassifed from OCI For the Nine Months Ended September 30, reclassified from OCI For the Nine Months Ended September 30, Type 2015 2014 into income 2015 2014 Swap Agreements $ (28,531 ) $ (11,099 ) Interest expense $ (8,017 ) $ (6,782 ) 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 September 30, 2015, the Company had not posted any collateral related to these agreements. If the Company had breached any of these provisions as of September 30, 2015, it could have been required to settle its obligations under the agreements at their termination value of $20,800 including accrued interest.

Exchangeable Senior Notes

Exchangeable Senior Notes	9 Months Ended
	Sep. 30, 2015
Text Block [Abstract]
Exchangeable Senior Notes	8. 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 $11,500, 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 other assets 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 September 30, 2015 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 other assets 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 September 30, 2015 was approximately 18.14 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 September 30, 2015. Therefore, holders of the 2013 Notes may elect to exchange such notes during the quarter ended December 31, 2015. 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: September 30, 2015 December 31, 2014 Carrying amount of equity component - 2013 Notes $ — $ 14,496 Carrying amount of equity component - 2015 Notes 22,597 — Carrying amount of equity components $ 22,597 $ 14,496 Principal amount of liability component 2013 Notes $ 85,364 $ 250,000 Principal amount of liability component 2015 Notes 575,000 — Unamortized discount - equity component - 2013 Notes (2,851 ) (10,448 ) Unamortized discount - equity component - 2015 Notes (22,597 ) — Unamortized cash discount - 2013 Notes (698 ) (2,606 ) Net carrying amount of liability components $ 634,218 $ 236,946 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 September 30, For the Nine Months Ended September 30, 2015 2014 2015 2014 Contractual interest $ 1,972 $ 1,484 $ 4,940 $ 4,452 Amortization of discount 805 679 2,198 2,004 Total interest expense recognized $ 2,777 $ 2,163 $ 7,138 $ 6,456 Repurchase of 2013 Notes As part of the 2015 Notes offering, the Company repurchased $164,636 of the 2013 Notes for $227,212 on September 15, 2015. 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: September 15, 2015 Principal amount repurchased $ 164,636 Amount allocated to: Extinguishment of liability component $ 157,100 Reacquisition of equity component 70,112 Total cash paid for repurchase $ 227,212 Exchangeable senior notes repurchased $ 164,636 Extinguishment of liability component (157,100 ) Discount on exchangeable senior notes (6,931 ) Related debt issuance costs (605 ) Gain/(Loss) on repurchase $ —

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2015
Equity [Abstract]
Stockholders' Equity	9. STOCKHOLDERS’ EQUITY On June 22, 2015, the Company issued and sold 6,325,000 shares of its common stock in a public offering at a price of $68.15 per share. The Company received gross proceeds of $431,049. The underwriting discount and transaction costs were $14,406, resulting in net proceeds of $416,643. 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. Under the terms of the equity distribution agreements, the Company may from time to time offer and sell shares of common stock, up to the aggregate offering price of $400,000, through its sales agents. During the three months ended September 30, 2015, the Company sold 410,000 shares of common stock at an average sales price of $75.17 per share, resulting in net proceeds of $30,266.

Noncontrolling Interests

Noncontrolling Interests	9 Months Ended
	Sep. 30, 2015
Noncontrolling Interests	12. OTHER NONCONTROLLING INTERESTS Other noncontrolling interests represent the ownership interest of third parties in two consolidated joint ventures as of September 30, 2015. Each of these consolidated joint ventures owns a single operating store, one in California, and one 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	11. 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 92.7% ownership interest in the Operating Partnership as of September 30, 2015. The remaining ownership interests in the Operating Partnership (including Preferred Operating Partnership units) of 7.3% 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 September 30, 2015 was $76.04 and there were 5,934,360 OP Units outstanding. Assuming that all of the OP Unit holders exercised their right to redeem all of their OP Units on September 30, 2015 and the Company elected to pay the OP Unit holders cash, the Company would have paid $451,249 in cash consideration to redeem the units. On June 18, 2015, the Company purchased one store located in Florida. As part of the consideration for this acquisition, 71,054 OP Units were issued with a total value of $4,773. On April 15, 2015, the Company purchased 22 stores located in Arizona and Texas. As part of the consideration for this acquisition, 1,504,277 OP Units were issued with a total value of $101,749. 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	10. 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. 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% per annum. 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. 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 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. Subsequent to this redemption, the fixed priority return is calculated using the current liquidation value of $101,699. 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 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 $41,903. Holders of the Series B Units receive distributions at an annual rate of 6%. These distributions are cumulative. The Series B Units will become redeemable at the option of the holder on the first anniversary of the date of issuance, which redemption obligation may be satisfied at the Company’s option in cash or shares of its common stock. 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 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 will become 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 will also become 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 will become redeemable at the option of the holder on the first anniversary of the date of issuance, which redemption obligation may be satisfied at the Company’s option in cash or shares of its common stock.

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	9 Months Ended
	Sep. 30, 2015
Equity Method Investments and Joint Ventures [Abstract]
Equity in Earnings of Unconsolidated Real Estate Ventures - Gain on Sale of Real Estate and Purchase of Joint Venture Partners' Interests	13. EQUITY IN EARNINGS OF UNCONSOLIDATED REAL ESTATE VENTURES—GAIN ON SALE OF REAL ESTATE AND PURCHASE OF JOINT VENTURE PARTNERS’ INTERESTS 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.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2015
Segment Reporting [Abstract]
Segment Information	14. 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: September 30, 2015 December 31, 2014 Balance Sheet Investment in unconsolidated real estate ventures Rental operations $ 84,671 $ 85,711 Total assets Rental operations $ 4,459,668 $ 4,109,673 Tenant reinsurance 36,023 39,383 Property management, acquisition and development 1,507,145 253,051 $ 6,002,836 $ 4,402,107 For the Three Months For the Nine Months 2015 2014 2015 2014 Statement of Operations Total revenues Rental operations $ 170,548 $ 144,669 $ 480,466 $ 415,448 Tenant reinsurance 18,226 15,385 52,076 43,356 Property management, acquisition and development 8,723 9,013 23,969 23,167 197,497 169,067 556,511 481,971 Operating expenses, including depreciation and amortization Rental operations 77,436 70,520 230,271 209,082 Tenant reinsurance 3,608 2,930 9,819 8,133 Property management, acquisition and development 19,149 18,124 62,074 56,204 100,193 91,574 302,164 273,419 Income (loss) from operations Rental operations 93,112 74,149 250,195 206,366 Tenant reinsurance 14,618 12,455 42,257 35,223 Property management, acquisition and development (10,426 ) (9,111 ) (38,105 ) (33,037 ) 97,304 77,493 254,347 208,552 Gain (loss) on real estate transactions and earnout from prior acquisitions Property management, acquisition and development 1,101 (2,500 ) 1,501 (10,285 ) Interest expense Rental operations (20,034 ) (20,416 ) (63,894 ) (60,074 ) Property management, acquisition and development (777 ) (265 ) (1,159 ) (863 ) (20,811 ) (20,681 ) (65,053 ) (60,937 ) Non-cash interest expense related to the amortization of discount on equity component of exchangeable senior notes Property management, acquisition and development (805 ) (679 ) (2,198 ) (2,004 ) Interest income Tenant reinsurance 3 5 11 13 Property management, acquisition and development 353 181 1,629 1,154 356 186 1,640 1,167 Interest income on note receivable from Preferred Operating Partnership unit holder Property management, acquisition and development 1,213 1,213 3,638 3,638 Equity in earnings of unconsolidated real estate ventures Rental operations 3,403 2,777 9,054 7,800 Equity in earnings of unconsolidated real estate ventures - gain on sale of real estate assets and purchase of partners’ interests Rental operations — 378 2,857 3,816 Income tax (expense) benefit Rental operations (325 ) (222 ) (1,404 ) (914 ) Tenant reinsurance (2,624 ) 2,011 (6,927 ) (5,660 ) Property management, acquisition and development (612 ) (783 ) 337 1,237 (3,561 ) 1,006 (7,994 ) (5,337 ) Net income (loss) Rental operations 76,156 56,666 196,808 156,994 Tenant reinsurance 11,997 14,471 35,341 29,576 Property management, acquisition and development (9,953 ) (11,944 ) (34,357 ) (40,160 ) $ 78,200 $ 59,193 $ 197,792 $ 146,410 Depreciation and amortization expense Rental operations $ 28,558 $ 27,226 $ 85,940 $ 80,012 Property management, acquisition and development 2,153 2,023 6,751 5,883 $ 30,711 $ 29,249 $ 92,691 $ 85,895 Statement of Cash Flows Acquisition of real estate assets Property management, acquisition and development $ (263,404 ) $ (328,235 ) Development and redevelopment of real estate assets Property management, acquisition and development $ (15,137 ) $ (11,288 )

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	15. COMMITMENTS AND CONTINGENCIES As of September 30, 2015, 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 several legal proceedings pending against it that include causes of action alleging wrongful foreclosure, violations of various state specific self-storage statutes, violations of various consumer fraud acts. As a result of these litigation matters, the Company recorded a liability of $850,000 during the year ended December 31, 2014, which is included in other liabilities on the condensed consolidated balance sheets. As of September 30, 2015, the Company was under contract to acquire seven operating stores and 14 stores to be acquired upon the completion of construction, for a total purchase price of $203,033. Of these stores, six are scheduled to close in 2015. The remaining stores will close upon completion of construction, expected to occur on various dates in 2016, 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	9 Months Ended
	Sep. 30, 2015
Subsequent Events [Abstract]
Subsequent Events	16. SUBSEQUENT EVENTS On October 1, 2015, the Company completed its previously announced acquisition of SmartStop Self Storage, Inc. (“SmartStop”), a public, non–traded REIT (“the Transaction”). The Company completed the Transaction as part of its strategy to acquire stores and portfolios of stores that can increase stockholder value. SmartStop stockholders received $13.75 per share in cash, which represents a total purchase price of approximately $1,400,000. The Company paid approximately $1,310,000, and the remaining $90,000 came from the sale of certain assets by SmartStop prior to the closing. In connection with the Transaction, the Company acquired 122 SmartStop stores and assumed the management of 43 third-party stores. Other disclosures relating to the Transaction, including pro forma financial information, are not practicable to include as the Company has not yet completed its initial accounting for the Transaction, and the information necessary for these disclosures is not yet available. On October 1, 2015, the Company closed on a $300,000 loan with a single lender that is secured by 47 stores. The loan bears interest at one month LIBOR plus 1.60% and matures September 30, 2022. An interest rate cap on 90% of the loan balance was executed on October 2, 2015, under which LIBOR is capped at a maximum of 3.9%.

Basis of Presentation (Policies

Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2015
Accounting Policies [Abstract]
Reclassifications	Reclassifications Certain amounts in the Company’s 2014 consolidated financial statements and supporting note disclosures have been reclassified to conform to the current period presentation. Such reclassifications did not impact previously reported net income or accumulated deficit.
Recently Issued Accounting Standards	Recently Issued Accounting Standards In April 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-08, “ Presentation of Financial Statements (Topic 205) and Property, Plant and Equipment (Topic 360): Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity. In May 2014, the FASB issued 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 2015-03, “ Interest - Imputation of Interest: Simplifying the Presentation of Debt Issuance Costs, 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,
Fair Value Disclosures	Derivative Financial Instruments Currently, the Company uses interest rate swaps to manage its interest rate risk. The valuation of these instruments is determined using widely accepted valuation techniques, including discounted cash flow analysis on the expected cash flows of each derivative. This analysis reflects the contractual terms of the derivatives, including the period to maturity, and uses observable market-based inputs, including interest rate curves. The fair values of interest rate swaps are determined using the market standard methodology of netting the discounted future fixed cash payments and the discounted expected variable cash receipts. The variable cash receipts are based on an expectation of future interest rates (forward curves) derived from observable market interest rate forward curves. The Company incorporates credit valuation adjustments to appropriately reflect both its own nonperformance risk and the respective counterparty’s nonperformance risk in the fair value measurements. In adjusting the fair value of its derivative contracts for the effect of nonperformance risk, the Company has considered the impact of netting and any applicable credit enhancements, such as collateral postings, thresholds, mutual puts and guarantees. In conjunction with the Financial Accounting Standards Board’s fair value measurement guidance, the Company made an accounting policy election to measure the credit risk of its derivative financial instruments that are subject to master netting agreements on a net basis by counterparty portfolio. Although the Company has determined that the majority of the inputs used to value its derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with its derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default by the Company and its counterparties. However, as of September 30, 2015, 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 September 30, 2015, aggregated by the level in the fair value hierarchy within which those measurements fall. Fair Value Measurements at Reporting Date Using Description September 30, Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Other assets - Cash Flow Hedge Swap Agreements $ 142 $ — $ 142 $ — Other liabilities - Cash Flow Hedge Swap Agreements $ (20,403 ) $ — $ (20,403 ) $ — The Company did not have any significant assets or liabilities that are re-measured on a recurring basis using significant unobservable inputs as of September 30, 2015 or December 31, 2014. 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, a valuation allowance is established. The operations of assets held for sale or sold during the period are presented as part of normal operations for all periods presented. The Company assesses 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 September 30, 2015 and December 31, 2014 approximate fair value. The fair values of the Company’s notes receivable from Preferred Operating Partnership unit holders 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: September 30, 2015 December 31, 2014 Fair Carrying Fair Carrying Notes receivable from Preferred Operating Partnership unit holders $ 130,402 $ 120,230 $ 126,380 $ 120,230 Fixed rate notes payable and notes payable to trusts $ 1,963,291 $ 1,834,199 $ 1,320,370 $ 1,283,893 Exchangeable senior notes $ 695,047 $ 660,364 $ 276,095 $ 250,000
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 September 30, 2015 and 2014, options to purchase approximately 82,571 and 29,547 shares of common stock, respectively, and for the nine months ended September 30, 2015 and 2014, options to purchase 50,144 and 27,045 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. For the Three Months Ended September 30, 2015 September 30, 2014 Number of Equivalent (if converted) Number of Equivalent (if converted) Series B Units 1,676,087 572,121 1,676,087 793,602 Series C Units 704,016 404,684 704,016 561,346 Series D Units 548,390 187,189 — — 2,928,493 1,163,994 2,380,103 1,354,948 For the Nine Months Ended September 30, 2015 September 30, 2014 Number of Equivalent (if converted) Number of Equivalent (if converted) Series B Units 1,676,087 607,806 1,563,746 777,364 Series C Units 704,016 429,926 571,973 478,824 Series D Units 548,390 198,865 — — 2,928,493 1,236,597 2,135,719 1,256,188 The Operating Partnership had $85,364 of its 2.375% Exchangeable Senior Notes due 2033 (the “2013 Notes”) issued and outstanding as of September 30, 2015. 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 $55.12 per share as of September 30, 2015, 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 September 30, 2015 (see footnote 8). 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 September 30, 2015, and could change over time as described in the indenture. The Company has irrevocably agreed to pay only cash for the accreted principal amount of the 2015 Notes relative to its exchange obligations, but retained the right to satisfy the exchange obligation in excess of the accreted principal amount in cash and/or common stock. Though the Company has retained that right, Accounting Standards Codification (“ASC”) 260, “Earnings per Share,” 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 September 30, 2015 of $41,903 by the closing price of the Company’s common stock as of September 30, 2015 of $77.16 per share. 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 September 30, 2015 of $29,639 by the closing price of the Company’s common stock as of September 30, 2015 of $77.16 per share. 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 September 30, 2015 of $13,710 by the closing price of the Company’s common stock as of September 30, 2015 of $77.16 per share.
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)	9 Months Ended
	Sep. 30, 2015
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 September 30, 2015, aggregated by the level in the fair value hierarchy within which those measurements fall. Fair Value Measurements at Reporting Date Using Description September 30, Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Other assets - Cash Flow Hedge Swap Agreements $ 142 $ — $ 142 $ — Other liabilities - Cash Flow Hedge Swap Agreements $ (20,403 ) $ — $ (20,403 ) $ —
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: September 30, 2015 December 31, 2014 Fair Carrying Fair Carrying Notes receivable from Preferred Operating Partnership unit holders $ 130,402 $ 120,230 $ 126,380 $ 120,230 Fixed rate notes payable and notes payable to trusts $ 1,963,291 $ 1,834,199 $ 1,320,370 $ 1,283,893 Exchangeable senior notes $ 695,047 $ 660,364 $ 276,095 $ 250,000

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	9 Months Ended
	Sep. 30, 2015
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. For the Three Months Ended September 30, 2015 September 30, 2014 Number of Equivalent (if converted) Number of Equivalent (if converted) Series B Units 1,676,087 572,121 1,676,087 793,602 Series C Units 704,016 404,684 704,016 561,346 Series D Units 548,390 187,189 — — 2,928,493 1,163,994 2,380,103 1,354,948 For the Nine Months Ended September 30, 2015 September 30, 2014 Number of Equivalent (if converted) Number of Equivalent (if converted) Series B Units 1,676,087 607,806 1,563,746 777,364 Series C Units 704,016 429,926 571,973 478,824 Series D Units 548,390 198,865 — — 2,928,493 1,236,597 2,135,719 1,256,188
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 For the Nine Months 2015 2014 2015 2014 Net income attributable to common stockholders $ 71,718 $ 54,228 $ 180,799 $ 133,233 Earnings and dividends allocated to participating securities (173 ) (125 ) (432 ) (366 ) Earnings for basic computations 71,545 54,103 180,367 132,867 Earnings and dividends allocated to participating securities 173 125 — 366 Income allocated to noncontrolling interest - Preferred Operating Partnership (Series A Units) and Operating Partnership 5,151 3,875 13,062 10,318 Fixed component of income allocated to noncontrolling interest - Preferred Operating Partnership (Series A Units) (1,272 ) (1,438 ) (3,817 ) (4,313 ) Net income for diluted computations $ 75,597 $ 56,665 $ 189,612 $ 139,238 Weighted average common shares outstanding: Average number of common shares outstanding - basic 122,644,837 115,726,911 118,564,872 115,606,845 Series A Units 875,480 989,980 875,480 989,980 OP Units 5,934,539 4,334,118 5,320,130 4,334,118 Unvested restricted stock awards included for treasury stock method 304,610 294,616 — 321,346 Shares related to 2013 exchangeable senior notes and dilutive stock options 638,645 271,929 645,831 299,600 Average number of common shares outstanding - diluted 130,398,111 121,617,554 125,406,313 121,551,889 Earnings per common share Basic $ 0.58 $ 0.47 $ 1.52 $ 1.15 Diluted $ 0.58 $ 0.47 $ 1.51 $ 1.15

Store Acquisitions (Tables)

Store Acquisitions (Tables)	9 Months Ended
	Sep. 30, 2015
Business Combinations [Abstract]
Schedule of Operating Properties Acquired	The following table summarizes the Company’s acquisitions of operating stores for the nine months ended September 30, 2015, and does not include purchases of raw land or improvements made to existing assets: Consideration Paid Acquisition Date Fair Value Property Location Number Date of Total Cash Paid Non-cash Notes Previous Net Value of Number of Land Building Intangible Closing Maryland 1 9/10/2015 $ 6,165 $ 6,183 $ — $ — $ — $ (18 ) $ — — $ 794 $ 5,178 $ 119 $ 74 North Carolina 1 6/19/2015 6,987 6,926 — — — 61 — — 1,408 5,461 107 11 Florida 1 6/18/2015 17,657 12,677 — — — 207 4,773 71,054 — 17,220 327 110 Florida (3) 1 6/17/2015 6,076 412 1,100 4,601 — (37 ) — — 534 5,364 125 53 Illinois 1 6/8/2015 10,046 9,970 — — — 76 — — 964 9,085 — (3 ) Massachusetts 1 5/13/2015 12,512 12,515 — — — (3 ) — — 1,625 10,875 — 12 Georgia 1 5/7/2015 6,498 6,458 — — — 40 — — 2,087 4,295 114 2 North Carolina 1 5/5/2015 11,007 10,976 — — — 31 — — 4,050 6,867 77 13 Georgia 1 4/24/2015 6,500 6,451 — — — 49 — — 370 6,014 114 2 Arizona, Texas 22 4/15/2015 178,252 75,681 — — — 822 101,749 1,504,277 24,087 151,465 2,121 579 Texas 1 4/14/2015 8,650 8,580 — — — 70 — — 619 7,861 160 10 California (2) 1 3/30/2015 12,699 1,700 1,629 11,009 (1,264 ) (375 ) — — 1,025 11,479 195 — South Carolina 2 3/30/2015 13,165 13,143 — — — 22 — — 1,763 11,229 144 29 Virginia 1 3/17/2015 5,073 5,065 — — — 8 — — 118 4,797 81 77 Texas 1 2/24/2015 13,570 13,519 — — — 51 — — 1,511 11,861 182 16 Texas 3 1/13/2015 41,904 41,806 — — — 98 — — 12,080 29,489 300 35 2015 Totals 40 $ 356,761 $ 232,062 $ 2,729 $ 15,610 $ (1,264 ) $ 1,102 $ 106,522 1,575,331 $ 53,035 $ 298,540 $ 4,166 $ 1,020 (1) This column represents costs paid at closing. The amounts shown exclude other acquisition costs paid before or after the closing date. (2) This represents the acquisition of a joint venture partners’ interest in Extra Space of Sacramento One LLC (“Sacramento One”), an existing joint venture, for $1,700 in cash. The result of the acquisition is that the Company owns 100% of Sacramento One, which owned one store located in California. Prior to the acquisition date, the Company accounted for its interest in Sacramento One as an equity-method investment, and the Company also held mortgage notes receivable from Sacramento One totalling $11,009, including related interest. The total acquisition date fair value of the Company’s previous equity interest was approximately $365 and is included in consideration transfered. The Company recognized a non-cash gain of $1,629 as a result of remeasuring the fair value of its equity interest held prior to the acquisition. The store is consolidated subsequent to the acquisition as the Company owns 100% of the store. (3) The Company determined the consideration paid for this store was below its market value, and recognized a $1,100 gain, representing the difference bewteen the fair value of the store and the consideration paid.

Variable Interests (Tables)

Variable Interests (Tables)	9 Months Ended
	Sep. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Liabilities and Maximum Exposure to Loss Related to Trusts	Following is a tabular comparison of the 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 September 30, 2015: 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 $ —

Derivatives (Tables)

Derivatives (Tables)	9 Months Ended
	Sep. 30, 2015
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 September 30, 2015 December 31, 2014 Derivatives designated as hedging instruments: Fair Value Other assets $ 142 $ 3,583 Other liabilities $ (20,403 ) $ (3,533 )
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 For the Three Months Ended September 30, Type Income (Expense) 2015 2014 Swap Agreements Interest expense $ (3,084 ) $ (2,172 ) Classification of For the Nine Months Ended September 30, Type Income (Expense) 2015 2014 Swap Agreements Interest expense $ (8,017 ) $ (6,782 )
Schedule of Information Relating to Gain (Loss) Recognized on Swap Agreements	Gain (loss) recognized in OCI Location of amounts Gain (loss) reclassifed from OCI For the Three Months Ended September 30, reclassified from OCI For the Three Months Ended September 30, Type 2015 2014 into income 2015 2014 Swap Agreements $ (23,073 ) $ 1,824 Interest expense $ (3,084 ) $ (2,172 ) Gain (loss) recognized in OCI Location of amounts Gain (loss) reclassifed from OCI For the Nine Months Ended September 30, reclassified from OCI For the Nine Months Ended September 30, Type 2015 2014 into income 2015 2014 Swap Agreements $ (28,531 ) $ (11,099 ) Interest expense $ (8,017 ) $ (6,782 )

Exchangeable Senior Notes (Tabl

Exchangeable Senior Notes (Tables)	9 Months Ended
	Sep. 30, 2015
Text Block [Abstract]
Summary of Repurchase of Debt	Information about the repurchase is as follows: September 15, 2015 Principal amount repurchased $ 164,636 Amount allocated to: Extinguishment of liability component $ 157,100 Reacquisition of equity component 70,112 Total cash paid for repurchase $ 227,212 Exchangeable senior notes repurchased $ 164,636 Extinguishment of liability component (157,100 ) Discount on exchangeable senior notes (6,931 ) Related debt issuance costs (605 ) Gain/(Loss) on repurchase $ —
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: September 30, 2015 December 31, 2014 Carrying amount of equity component - 2013 Notes $ — $ 14,496 Carrying amount of equity component - 2015 Notes 22,597 — Carrying amount of equity components $ 22,597 $ 14,496 Principal amount of liability component 2013 Notes $ 85,364 $ 250,000 Principal amount of liability component 2015 Notes 575,000 — Unamortized discount - equity component - 2013 Notes (2,851 ) (10,448 ) Unamortized discount - equity component - 2015 Notes (22,597 ) — Unamortized cash discount - 2013 Notes (698 ) (2,606 ) Net carrying amount of liability components $ 634,218 $ 236,946
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 September 30, For the Nine Months Ended September 30, 2015 2014 2015 2014 Contractual interest $ 1,972 $ 1,484 $ 4,940 $ 4,452 Amortization of discount 805 679 2,198 2,004 Total interest expense recognized $ 2,777 $ 2,163 $ 7,138 $ 6,456

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2015
Segment Reporting [Abstract]
Schedule of Financial Information of Business Segments	Financial information for the Company’s business segments is presented below: September 30, 2015 December 31, 2014 Balance Sheet Investment in unconsolidated real estate ventures Rental operations $ 84,671 $ 85,711 Total assets Rental operations $ 4,459,668 $ 4,109,673 Tenant reinsurance 36,023 39,383 Property management, acquisition and development 1,507,145 253,051 $ 6,002,836 $ 4,402,107 For the Three Months For the Nine Months 2015 2014 2015 2014 Statement of Operations Total revenues Rental operations $ 170,548 $ 144,669 $ 480,466 $ 415,448 Tenant reinsurance 18,226 15,385 52,076 43,356 Property management, acquisition and development 8,723 9,013 23,969 23,167 197,497 169,067 556,511 481,971 Operating expenses, including depreciation and amortization Rental operations 77,436 70,520 230,271 209,082 Tenant reinsurance 3,608 2,930 9,819 8,133 Property management, acquisition and development 19,149 18,124 62,074 56,204 100,193 91,574 302,164 273,419 Income (loss) from operations Rental operations 93,112 74,149 250,195 206,366 Tenant reinsurance 14,618 12,455 42,257 35,223 Property management, acquisition and development (10,426 ) (9,111 ) (38,105 ) (33,037 ) 97,304 77,493 254,347 208,552 Gain (loss) on real estate transactions and earnout from prior acquisitions Property management, acquisition and development 1,101 (2,500 ) 1,501 (10,285 ) Interest expense Rental operations (20,034 ) (20,416 ) (63,894 ) (60,074 ) Property management, acquisition and development (777 ) (265 ) (1,159 ) (863 ) (20,811 ) (20,681 ) (65,053 ) (60,937 ) Non-cash interest expense related to the amortization of discount on equity component of exchangeable senior notes Property management, acquisition and development (805 ) (679 ) (2,198 ) (2,004 ) Interest income Tenant reinsurance 3 5 11 13 Property management, acquisition and development 353 181 1,629 1,154 356 186 1,640 1,167 Interest income on note receivable from Preferred Operating Partnership unit holder Property management, acquisition and development 1,213 1,213 3,638 3,638 Equity in earnings of unconsolidated real estate ventures Rental operations 3,403 2,777 9,054 7,800 Equity in earnings of unconsolidated real estate ventures - gain on sale of real estate assets and purchase of partners’ interests Rental operations — 378 2,857 3,816 Income tax (expense) benefit Rental operations (325 ) (222 ) (1,404 ) (914 ) Tenant reinsurance (2,624 ) 2,011 (6,927 ) (5,660 ) Property management, acquisition and development (612 ) (783 ) 337 1,237 (3,561 ) 1,006 (7,994 ) (5,337 ) Net income (loss) Rental operations 76,156 56,666 196,808 156,994 Tenant reinsurance 11,997 14,471 35,341 29,576 Property management, acquisition and development (9,953 ) (11,944 ) (34,357 ) (40,160 ) $ 78,200 $ 59,193 $ 197,792 $ 146,410 Depreciation and amortization expense Rental operations $ 28,558 $ 27,226 $ 85,940 $ 80,012 Property management, acquisition and development 2,153 2,023 6,751 5,883 $ 30,711 $ 29,249 $ 92,691 $ 85,895 Statement of Cash Flows Acquisition of real estate assets Property management, acquisition and development $ (263,404 ) $ (328,235 ) Development and redevelopment of real estate assets Property management, acquisition and development $ (15,137 ) $ (11,288 )

Organization - Additional Infor

Organization - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2015StoreSegments
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of operating storage facilities in which the entity has equity interests (in stores)	868
Number of stores owned by franchisees and third parties	302
Number of operating stores owned and/or managed	1,170
Number of states in which operating storage facilities are located	36
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	Sep. 30, 2015USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets - Cash Flow Hedge Swap Agreements	$ 142
Other liabilities - Cash Flow Hedge Swap Agreements	(20,403)
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	142
Other liabilities - Cash Flow Hedge Swap Agreements	$ (20,403)

Fair Value Disclosures - Sche33

Fair Value Disclosures - Schedule of Fair Value of Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Fair Value of Financial Instruments [Line Items]
Notes receivable from Preferred Operating Partnership unit holders	$ 120,230	$ 120,230
Exchangeable senior notes	660,364	250,000
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 payable and notes payable to trusts	1,834,199	1,283,893
Exchangeable senior notes	660,364	250,000
Fair Value [Member]
Fair Value of Financial Instruments [Line Items]
Notes receivable from Preferred Operating Partnership unit holders	130,402	126,380
Fixed rate notes payable and notes payable to trusts	1,963,291	1,320,370
Exchangeable senior notes	$ 695,047	$ 276,095

Earnings Per Common Share - Add

Earnings Per Common Share - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Jun. 21, 2013
Earnings Per Common Share [Line Items]
Average closing price of common stock	$ 77.16		$ 77.16
Series A Units [Member]
Earnings Per Common Share [Line Items]
Exchangeable preferred operating partnership units settled in cash, minimum	$ 115,000,000		$ 115,000,000
Series B Units [Member]
Earnings Per Common Share [Line Items]
Units outstanding	41,903,000		41,903,000
Series C Units [Member]
Earnings Per Common Share [Line Items]
Units outstanding	29,639,000		29,639,000
Series D Units [Member]
Earnings Per Common Share [Line Items]
Units outstanding	13,710,000		13,710,000
Operating Partnership [Member] | 2.375% Exchangeable Senior Notes due 2033 (the 2013 Notes) [Member]
Earnings Per Common Share [Line Items]
Principal amount of notes issued	$ 85,364,000		$ 85,364,000		$ 250,000,000
Interest rate	2.375%		2.375%		2.375%
Exchange price	$ 55.12		$ 55.12
Shares related to the Notes were included in the computation for diluted earnings per share	383,279	0	383,279	0
Operating Partnership [Member] | Exchangeable Senior Notes 3.125% due 2035 (the 2015 Notes) [Member]
Earnings Per Common Share [Line Items]
Principal amount of notes issued	$ 575,000,000		$ 575,000,000
Interest rate	3.125%		3.125%
Exchange price	$ 95.40		$ 95.40
Shares related to the Notes were included in the computation for diluted earnings per share	0	0	0	0
Stock Options [Member]
Earnings Per Common Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per common share	82,571	29,547	50,144	27,045

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		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of Units	2,928,493	2,380,103	2,928,493	2,135,719
Equivalent Shares (if converted)	1,163,994	1,354,948	1,236,597	1,256,188
Series B Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of Units	1,676,087	1,676,087	1,676,087	1,563,746
Equivalent Shares (if converted)	572,121	793,602	607,806	777,364
Series C Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of Units	704,016	704,016	704,016	571,973
Equivalent Shares (if converted)	404,684	561,346	429,926	478,824
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)	187,189		198,865

Earnings Per Common Share - S36

Earnings Per Common Share - Schedule of Computation of Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Net income attributable to common stockholders	$ 71,718	$ 54,228	$ 180,799	$ 133,233
Earnings and dividends allocated to participating securities	(173)	(125)	(432)	(366)
Earnings for basic computations	71,545	54,103	180,367	132,867
Earnings and dividends allocated to participating securities	173	125		366
Income allocated to noncontrolling interest - Preferred Operating Partnership (Series A Units) and Operating Partnership	5,151	3,875	13,062	10,318
Fixed component of income allocated to noncontrolling interest - Preferred Operating Partnership (Series A Units)	(1,272)	(1,438)	(3,817)	(4,313)
Net income for diluted computations	$ 75,597	$ 56,665	$ 189,612	$ 139,238
Weighted average common shares outstanding:
Average number of common shares outstanding - basic	122,644,837	115,726,911	118,564,872	115,606,845
Series A Units	875,480	989,980	875,480	989,980
OP Units	5,934,539	4,334,118	5,320,130	4,334,118
Unvested restricted stock awards included for treasury stock method	304,610	294,616		321,346
Shares related to 2013 exchangeable senior notes and dilutive stock options	638,645	271,929	645,831	299,600
Average number of common shares outstanding - diluted	130,398,111	121,617,554	125,406,313	121,551,889
Earnings per common share
Basic	$ 0.58	$ 0.47	$ 1.52	$ 1.15
Diluted	$ 0.58	$ 0.47	$ 1.51	$ 1.15

Store Acquisitions - Schedule o

Store Acquisitions - Schedule of Operating Properties Acquired (Detail) $ in Thousands	Mar. 31, 2015USD ($)	Sep. 30, 2015USD ($)Propertyshares	Sep. 30, 2014USD ($)
Property Acquisitions [Line Items]
Number of Stores | Property		40
Total Consideration Paid		$ 356,761
Cash Consideration Paid		232,062
Non-cash gain	$ 1,629	2,729
Notes Receivable	$ 11,009	15,610
Previous equity interest		(1,264)
Net Liabilities/(Assets) Assumed		1,102
Value of OP units issued		$ 106,522	$ 22,118
Number of OP Units Issued | shares		1,575,331
Acquisition Date Fair Value, Land		$ 53,035
Acquisition Date Fair Value, Building		298,540
Acquisition Date Fair Value, Intangible		4,166
Closing costs-expensed		$ 1,020
Maryland 1 Property 9/10/2015 [Member]
Property Acquisitions [Line Items]
Number of Stores | Property		1
Total Consideration Paid		$ 6,165
Cash Consideration Paid		6,183
Net Liabilities/(Assets) Assumed		(18)
Acquisition Date Fair Value, Land		794
Acquisition Date Fair Value, Building		5,178
Acquisition Date Fair Value, Intangible		119
Closing costs-expensed		$ 74
North Carolina 1 Property 6/19/2015 [Member]
Property Acquisitions [Line Items]
Number of Stores | Property		1
Total Consideration Paid		$ 6,987
Cash Consideration Paid		6,926
Net Liabilities/(Assets) Assumed		61
Acquisition Date Fair Value, Land		1,408
Acquisition Date Fair Value, Building		5,461
Acquisition Date Fair Value, Intangible		107
Closing costs-expensed		$ 11
Florida 1 Property 6/18/2015 [Member]
Property Acquisitions [Line Items]
Number of Stores | Property		1
Total Consideration Paid		$ 17,657
Cash Consideration Paid		12,677
Net Liabilities/(Assets) Assumed		207
Value of OP units issued		$ 4,773
Number of OP Units Issued | shares		71,054
Acquisition Date Fair Value, Building		$ 17,220
Acquisition Date Fair Value, Intangible		327
Closing costs-expensed		$ 110
Florida 1 Property 6/17/2015 [Member]
Property Acquisitions [Line Items]
Number of Stores | Property		1
Total Consideration Paid		$ 6,076
Cash Consideration Paid		412
Non-cash gain		1,100
Notes Receivable		4,601
Net Liabilities/(Assets) Assumed		(37)
Acquisition Date Fair Value, Land		534
Acquisition Date Fair Value, Building		5,364
Acquisition Date Fair Value, Intangible		125
Closing costs-expensed		$ 53
Illinois 1 Property 6/8/2015 [Member]
Property Acquisitions [Line Items]
Number of Stores | Property		1
Total Consideration Paid		$ 10,046
Cash Consideration Paid		9,970
Net Liabilities/(Assets) Assumed		76
Acquisition Date Fair Value, Land		964
Acquisition Date Fair Value, Building		9,085
Closing costs-expensed		$ (3)
Massachusetts 1 Property 5/13/2015 [Member]
Property Acquisitions [Line Items]
Number of Stores | Property		1
Total Consideration Paid		$ 12,512
Cash Consideration Paid		12,515
Net Liabilities/(Assets) Assumed		(3)
Acquisition Date Fair Value, Land		1,625
Acquisition Date Fair Value, Building		10,875
Closing costs-expensed		$ 12
Georgia 1 Property 5/7/2015 [Member]
Property Acquisitions [Line Items]
Number of Stores | Property		1
Total Consideration Paid		$ 6,498
Cash Consideration Paid		6,458
Net Liabilities/(Assets) Assumed		40
Acquisition Date Fair Value, Land		2,087
Acquisition Date Fair Value, Building		4,295
Acquisition Date Fair Value, Intangible		114
Closing costs-expensed		$ 2
North Carolina 1 Property 5/5/2015 [Member]
Property Acquisitions [Line Items]
Number of Stores | Property		1
Total Consideration Paid		$ 11,007
Cash Consideration Paid		10,976
Net Liabilities/(Assets) Assumed		31
Acquisition Date Fair Value, Land		4,050
Acquisition Date Fair Value, Building		6,867
Acquisition Date Fair Value, Intangible		77
Closing costs-expensed		$ 13
Georgia 1 Property 4/24/2015 [Member]
Property Acquisitions [Line Items]
Number of Stores | Property		1
Total Consideration Paid		$ 6,500
Cash Consideration Paid		6,451
Net Liabilities/(Assets) Assumed		49
Acquisition Date Fair Value, Land		370
Acquisition Date Fair Value, Building		6,014
Acquisition Date Fair Value, Intangible		114
Closing costs-expensed		$ 2
Arizona Texas 22 Property 4/15/2015 [Member]
Property Acquisitions [Line Items]
Number of Stores | Property		22
Total Consideration Paid		$ 178,252
Cash Consideration Paid		75,681
Net Liabilities/(Assets) Assumed		822
Value of OP units issued		$ 101,749
Number of OP Units Issued | shares		1,504,277
Acquisition Date Fair Value, Land		$ 24,087
Acquisition Date Fair Value, Building		151,465
Acquisition Date Fair Value, Intangible		2,121
Closing costs-expensed		$ 579
Texas 1 Property 4/14/2015 [Member]
Property Acquisitions [Line Items]
Number of Stores | Property		1
Total Consideration Paid		$ 8,650
Cash Consideration Paid		8,580
Net Liabilities/(Assets) Assumed		70
Acquisition Date Fair Value, Land		619
Acquisition Date Fair Value, Building		7,861
Acquisition Date Fair Value, Intangible		160
Closing costs-expensed		$ 10
California 1 Property 3/30/2015 [Member]
Property Acquisitions [Line Items]
Number of Stores | Property		1
Total Consideration Paid		$ 12,699
Cash Consideration Paid		1,700
Non-cash gain		1,629
Notes Receivable		11,009
Previous equity interest		(1,264)
Net Liabilities/(Assets) Assumed		(375)
Acquisition Date Fair Value, Land		1,025
Acquisition Date Fair Value, Building		11,479
Acquisition Date Fair Value, Intangible		$ 195
South Carolina 2 Property 3/30/2015 [Member]
Property Acquisitions [Line Items]
Number of Stores | Property		2
Total Consideration Paid		$ 13,165
Cash Consideration Paid		13,143
Net Liabilities/(Assets) Assumed		22
Acquisition Date Fair Value, Land		1,763
Acquisition Date Fair Value, Building		11,229
Acquisition Date Fair Value, Intangible		144
Closing costs-expensed		$ 29
Virginia 1 Property 3/17/2015 [Member]
Property Acquisitions [Line Items]
Number of Stores | Property		1
Total Consideration Paid		$ 5,073
Cash Consideration Paid		5,065
Net Liabilities/(Assets) Assumed		8
Acquisition Date Fair Value, Land		118
Acquisition Date Fair Value, Building		4,797
Acquisition Date Fair Value, Intangible		81
Closing costs-expensed		$ 77
Texas 1 Property 2/24/2015 [Member]
Property Acquisitions [Line Items]
Number of Stores | Property		1
Total Consideration Paid		$ 13,570
Cash Consideration Paid		13,519
Net Liabilities/(Assets) Assumed		51
Acquisition Date Fair Value, Land		1,511
Acquisition Date Fair Value, Building		11,861
Acquisition Date Fair Value, Intangible		182
Closing costs-expensed		$ 16
Texas 3 Property 1/13/2015 [Member]
Property Acquisitions [Line Items]
Number of Stores | Property		3
Total Consideration Paid		$ 41,904
Cash Consideration Paid		41,806
Net Liabilities/(Assets) Assumed		98
Acquisition Date Fair Value, Land		12,080
Acquisition Date Fair Value, Building		29,489
Acquisition Date Fair Value, Intangible		300
Closing costs-expensed		$ 35

Store Acquisitions - Schedule38

Store Acquisitions - Schedule of Operating Properties Acquired (Parenthetical) (Detail) $ in Thousands	Mar. 31, 2015USD ($)	Sep. 30, 2015USD ($)Store	Jun. 11, 2015Store
Property Acquisitions [Line Items]
Number of operating stores owned by consolidated joint venture | Store			19
Non-cash gain	$ 1,629	$ 2,729
Company held mortgage notes receivable eliminated as a result of the acquisition	$ 11,009	15,610
Florida 1 Property 6/17/2015 [Member]
Property Acquisitions [Line Items]
Non-cash gain		1,100
Company held mortgage notes receivable eliminated as a result of the acquisition		4,601
Gain on bargain purchase of acquisition		1,100
Extra Space of Sacramento One LLC [Member]
Property Acquisitions [Line Items]
Cash portion of payment for acquisition		$ 1,700
Equity Ownership (as a percent)		100.00%
Number of operating stores owned by consolidated joint venture | Store		1
Previous equity interest, fair value		$ 365
Non-cash gain		1,629
Company held mortgage notes receivable eliminated as a result of the acquisition		$ 11,009

Variable Interests - Additional

Variable Interests - Additional Information (Detail)	Sep. 30, 2015ItemJointVenture
Variable Interests And Equity Method Investments Disclosure [Abstract]
Number of wholly-owned unconsolidated subsidiaries | Item	3
Number of interests in consolidated VIE joint ventures	0

Variable Interests - Schedule o

Variable Interests - Schedule of Liabilities and Maximum Exposure to Loss Related to Trusts (Detail) - USD ($)	Sep. 30, 2015	Dec. 31, 2014
Variable Interest Entity [Line Items]
Notes payable to trusts	$ 119,590,000	$ 119,590,000
Operating Partnership [Member] | Variable Interest Entity, Not Primary Beneficiary [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] | 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

Derivatives - Additional Inform

Derivatives - Additional Information (Detail) $ in Thousands	Sep. 30, 2015USD ($)Item
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Number of derivative financial instruments | Item	28
Combined notional amount	$ 1,110,145
Estimated termination value on settlement	$ 20,800

Derivatives - Schedule of Balan

Derivatives - Schedule of Balance Sheet Classification and Fair Value of Entity's Derivative Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Other Assets [Member]
Derivative [Line Items]
Other assets - Asset (Liability) Derivatives	$ 142	$ 3,583
Other Liabilities [Member]
Derivative [Line Items]
Other liabilities - Asset (Liability) Derivatives	$ (20,403)	$ (3,533)

Derivatives - Interest Payments

Derivatives - Interest Payments Recognized as Increase or Decrease in Interest Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Interest Rate Swap [Member]
Derivative [Line Items]
Swap agreements increase (decrease) in interest expenses due to interest payments	$ (3,084)	$ (2,172)	$ (8,017)	$ (6,782)

Derivatives - Schedule of Infor

Derivatives - Schedule of Information Relating to Gain (Loss) Recognized on Swap Agreements (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Swap agreements gain (loss) recognized in OCI	$ (23,073)	$ 1,824	$ (28,531)	$ (11,099)
Swap agreements gain (loss) reclassified from OCI - Interest expense	$ (3,084)	$ (2,172)	$ (8,017)	$ (6,782)

Exchangeable Senior Notes - Add

Exchangeable Senior Notes - Additional Information (Detail) $ in Thousands	Sep. 15, 2015USD ($)	Jun. 21, 2013USD ($)	Sep. 30, 2015USD ($)	Sep. 30, 2015USD ($)d	Sep. 30, 2015USD ($)	Dec. 31, 2014USD ($)
Debt Instrument [Line Items]
Unamortized cash discount			$ 26,146	$ 26,146	$ 26,146	$ 13,054
2.375% Exchangeable Senior Notes due 2033 (the 2013 Notes) [Member]
Debt Instrument [Line Items]
Effective interest rate on the liability component			4.00%	4.00%	4.00%
Notes exchange, threshold percentage				130.00%
Notes exchange, threshold trading days | d				20
Notes exchange, threshold consecutive trading days				30 days
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	$ 85,364	$ 85,364	$ 85,364
Interest rate		2.375%	2.375%	2.375%	2.375%
Issuance cost	$ 605	$ 1,672
Conversion ratio, number of shares per $1,000 principal amount, numerator					18.14
Principal amount used for debt instrument conversion ratio			$ 1,000	$ 1,000	$ 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	6,931	$ 3,750	$ 698	$ 698	$ 698	$ 2,606
Principal amount repurchased	164,636
Total cash paid for repurchase	$ 227,212
Exchangeable Senior Notes 3.125% due 2035 (the 2015 Notes) [Member]
Debt Instrument [Line Items]
Effective interest rate on the liability component			4.00%	4.00%	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	$ 575,000	$ 575,000
Interest rate			3.125%	3.125%	3.125%
Issuance cost			$ 11,500
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	$ 1,000	$ 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 - Sum

Exchangeable Senior Notes - Summary of Repurchase of Debt (Detail) - USD ($) $ in Thousands	Sep. 15, 2015	Jun. 21, 2013	Sep. 30, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Exchangeable senior notes repurchased			$ 660,364	$ 250,000
Discount on exchangeable senior notes			(26,146)	(13,054)
Operating Partnership [Member] | 2.375% Exchangeable Senior Notes due 2033 (the 2013 Notes) [Member]
Debt Instrument [Line Items]
Principal amount repurchased	$ 164,636
Extinguishment of liability component	157,100
Reacquisition of equity component	70,112
Total cash paid for repurchase	227,212
Exchangeable senior notes repurchased	164,636		85,364	250,000
Extinguishment of liability component	(157,100)
Discount on exchangeable senior notes	(6,931)	$ (3,750)	$ (698)	$ (2,606)
Related debt issuance costs	(605)	$ (1,672)
Gain/(Loss) on repurchase	$ 0

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	Sep. 30, 2015	Sep. 15, 2015	Dec. 31, 2014	Jun. 21, 2013
Debt Instrument [Line Items]
Principal amount of liability components	$ 660,364		$ 250,000
Unamortized cash discount	(26,146)		(13,054)
Operating Partnership [Member]
Debt Instrument [Line Items]
Carrying amount of equity components	22,597		14,496
Net carrying amount of liability components	634,218		236,946
Operating Partnership [Member] | 2.375% Exchangeable Senior Notes due 2033 (the 2013 Notes) [Member]
Debt Instrument [Line Items]
Carrying amount of equity components			14,496
Principal amount of liability components	85,364	$ 164,636	250,000
Unamortized discount - equity components	(2,851)		(10,448)
Unamortized cash discount	(698)	$ (6,931)	$ (2,606)	$ (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
Principal amount of liability components	575,000
Unamortized discount - equity components	$ (22,597)

Exchangeable Senior Notes - S48

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		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Debt Instrument [Line Items]
Amortization of discount	$ 805	$ 679	$ 2,198	$ 2,004
2.375% Exchangeable Senior Notes due 2033 (the 2013 Notes) [Member]
Debt Instrument [Line Items]
Contractual interest	1,972	1,484	4,940	4,452
Amortization of discount	805	679	2,198	2,004
Total interest expense recognized	$ 2,777	$ 2,163	$ 7,138	$ 6,456

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) $ / shares in Units, $ in Thousands	Aug. 28, 2015USD ($)SalesAgents	Jun. 22, 2015USD ($)$ / sharesshares	Sep. 30, 2015USD ($)$ / sharesshares	Sep. 30, 2015USD ($)$ / shares
Changes In Equity And Comprehensive Income Line Items [Line Items]
Offer price of shares of common stock sold in a public offering (in dollars per share) | $ / shares		$ 68.15
Gross proceeds from issuance of common stock		$ 431,049
Underwriting discount and transaction costs of stock issuance		14,406
Net proceeds from issuance of common stock		$ 416,643		$ 446,909
Public Offering [Member]
Changes In Equity And Comprehensive Income Line Items [Line Items]
Common stock issued and sold | shares		6,325,000
At the Market Equity Distribution Agreement [Member]
Changes In Equity And Comprehensive Income Line Items [Line Items]
Common stock issued and sold | shares			410,000
Net proceeds from issuance of common stock			$ 30,266
Number of sales agents | SalesAgents	5
Aggregate offering price of common share	$ 400,000
Average price per share | $ / shares			$ 75.17	$ 75.17

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	Sep. 30, 2015USD ($)	Dec. 31, 2014USD ($)
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
Preferred OP units, current liquidation value	$ 101,699

Noncontrolling Interest Repre51

Noncontrolling Interest Represented by Preferred Operating Partnership Units - Series B Redeemable Preferred Units - Additional Information (Detail) $ / shares in Units, $ in Thousands	Apr. 03, 2014USD ($)Storeshares	Sep. 26, 2013USD ($)Storeshares	Aug. 29, 2013Store	Sep. 30, 2015USD ($)$ / shares	Sep. 30, 2014USD ($)
Noncontrolling Interest in Operating Partnership [Line Items]
Debt assumed					$ 38,347
Series B Redeemable Preferred Units [Member] | Series B Units [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Liquidation value (in dollars per share) | $ / shares				$ 25
Fixed liquidation value				$ 41,903
Annual rate of return (as a percent)				6.00%
Series B Redeemable Preferred Units [Member] | 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
Series B Redeemable Preferred Units [Member] | 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
Series B Redeemable Preferred Units [Member] | 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
Series B Redeemable Preferred Units [Member] | 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 Repre52

Noncontrolling Interest Represented by Preferred Operating Partnership Units - Series C Convertible Redeemable Preferred Units - Additional Information (Detail) $ / shares in Units, $ in Thousands	Dec. 31, 2014USD ($)	Nov. 19, 2013Store	May. 31, 2014USD ($)Storeshares	Sep. 30, 2015USD ($)OperatingPartnershipUnits$ / shares	Sep. 30, 2014USD ($)
Noncontrolling Interest in Operating Partnership [Line Items]
Debt assumed					$ 38,347
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 | OperatingPartnershipUnits				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 interest 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 Repre53

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	Dec. 31, 2014	Sep. 30, 2015
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	Jun. 18, 2015USD ($)Storeshares	Apr. 15, 2015USD ($)Storeshares	Sep. 30, 2015USD ($)$ / 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			$ 76.04
Consideration to be paid on redemption of common OP units | $			$ 451,249
Operating Partnership [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Ownership interest held by entity (as a percent)			92.70%
Noncontrolling interest in operating partnership (as a percent)			7.30%
OP units outstanding			5,934,360
Operating Partnership [Member] | Arizona Texas 22 Property 4/15/2015 [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Number of stores acquired as part of portfolio acquisition | Store		22
Number of common units issued as part of acquisition		1,504,277
OP units issued as part of the acquisition | $		$ 101,749
Operating Partnership [Member] | Florida 1 Property 6/18/2015 [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Number of stores acquired as part of portfolio acquisition | Store	1
Number of common units issued as part of acquisition	71,054
OP units issued as part of the acquisition | $	$ 4,773

Other Noncontrolling Interests

Other Noncontrolling Interests - Additional Information (Detail) $ in Thousands	Jun. 11, 2015USD ($)Store	Sep. 30, 2015JointVenture
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
Number of operating stores owned by consolidated joint venture | Store	19
Other [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Number of consolidated joint ventures		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%
Other [Member] | California [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Number of consolidated joint ventures		1
Other [Member] | Texas [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Number of consolidated joint ventures		1

Equity in Earnings of Unconso56

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	Mar. 31, 2015USD ($)Store	Sep. 30, 2015USD ($)
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	$ 15,610
Equity ownership prior to the acquisition (as a percent)	17.60%
Non-cash gain	$ 1,629	$ 2,729
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

Segment Information - Additiona

Segment Information - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2015Segments
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		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Segment Reporting Information [Line Items]
Investment in unconsolidated real estate ventures	$ 84,671		$ 84,671		$ 85,711
Total assets	6,002,836		6,002,836		4,402,107
Total revenues	197,497	$ 169,067	556,511	$ 481,971
Operating expenses, including depreciation and amortization	100,193	91,574	302,164	273,419
Income (loss) from operations	97,304	77,493	254,347	208,552
Gain (loss) on real estate transactions and earnout from prior acquisitions	1,101	(2,500)	1,501	(10,285)
Interest income	356	186	1,640	1,167
Interest expense	(20,811)	(20,681)	(65,053)	(60,937)
Non-cash interest expense related to the amortization of discount on equity component of exchangeable senior notes	(805)	(679)	(2,198)	(2,004)
Interest income on note receivable from Preferred Operating Partnership unit holder	1,213	1,213	3,638	3,638
Equity in earnings of unconsolidated real estate ventures	3,403	2,777	9,054	7,800
Equity in earnings of unconsolidated real estate ventures - gain on sale of real assets and purchase of partners' interests		378	2,857	3,816
Income tax (expense) benefit	(3,561)	1,006	(7,994)	(5,337)
Net income (loss)	78,200	59,193	197,792	146,410
Depreciation and amortization expense	30,711	29,249	92,691	85,895
Acquisition of real estate assets			(263,404)	(328,235)
Development and redevelopment of real estate assets			(15,137)	(11,288)
Rental Operations [Member]
Segment Reporting Information [Line Items]
Investment in unconsolidated real estate ventures	84,671		84,671		85,711
Total assets	4,459,668		4,459,668		4,109,673
Total revenues	170,548	144,669	480,466	415,448
Operating expenses, including depreciation and amortization	77,436	70,520	230,271	209,082
Income (loss) from operations	93,112	74,149	250,195	206,366
Interest expense	(20,034)	(20,416)	(63,894)	(60,074)
Equity in earnings of unconsolidated real estate ventures	3,403	2,777	9,054	7,800
Equity in earnings of unconsolidated real estate ventures - gain on sale of real assets and purchase of partners' interests		378	2,857	3,816
Income tax (expense) benefit	(325)	(222)	(1,404)	(914)
Net income (loss)	76,156	56,666	196,808	156,994
Depreciation and amortization expense	28,558	27,226	85,940	80,012
Tenant Reinsurance [Member]
Segment Reporting Information [Line Items]
Total assets	36,023		36,023		39,383
Total revenues	18,226	15,385	52,076	43,356
Operating expenses, including depreciation and amortization	3,608	2,930	9,819	8,133
Income (loss) from operations	14,618	12,455	42,257	35,223
Interest income	3	5	11	13
Income tax (expense) benefit	(2,624)	2,011	(6,927)	(5,660)
Net income (loss)	11,997	14,471	35,341	29,576
Property Management Acquisition and Development [Member]
Segment Reporting Information [Line Items]
Total assets	1,507,145		1,507,145		$ 253,051
Total revenues	8,723	9,013	23,969	23,167
Operating expenses, including depreciation and amortization	19,149	18,124	62,074	56,204
Income (loss) from operations	(10,426)	(9,111)	(38,105)	(33,037)
Gain (loss) on real estate transactions and earnout from prior acquisitions	1,101	(2,500)	1,501	(10,285)
Interest income	353	181	1,629	1,154
Interest expense	(777)	(265)	(1,159)	(863)
Non-cash interest expense related to the amortization of discount on equity component of exchangeable senior notes	(805)	(679)	(2,198)	(2,004)
Interest income on note receivable from Preferred Operating Partnership unit holder	1,213	1,213	3,638	3,638
Income tax (expense) benefit	(612)	(783)	337	1,237
Net income (loss)	(9,953)	(11,944)	(34,357)	(40,160)
Depreciation and amortization expense	$ 2,153	$ 2,023	6,751	5,883
Acquisition of real estate assets			(263,404)	(328,235)
Development and redevelopment of real estate assets			$ (15,137)	$ (11,288)

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Thousands	Sep. 30, 2015USD ($)Stores	Dec. 31, 2014USD ($)
Commitments And Contingencies [Line Items]
Litigation liability recorded | $		$ 850,000
Contract Amount [Member]
Commitments And Contingencies [Line Items]
Number of stores to be acquired	7
Number of stores scheduled to be closed	6
Purchase price | $	$ 203,033
Contract Amount [Member] | Construction [Member]
Commitments And Contingencies [Line Items]
Number of stores to be acquired	14

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) $ / shares in Units, $ in Thousands	Oct. 02, 2015	Oct. 01, 2015USD ($)Stores$ / shares	Sep. 30, 2015USD ($)
Subsequent Event [Line Items]
Cash paid			$ 232,062
Subsequent Event [Member]
Subsequent Event [Line Items]
Repayment of loan		$ 300,000
Number of stores secured under debt facility | Stores		47
Maturity of loan		Sep. 30, 2022
Interest rate cap	90.00%
Subsequent Event [Member] | Libor [Member]
Subsequent Event [Line Items]
Basis spread on variable rate (as a percent)		1.60%
Subsequent Event [Member] | Maximum [Member] | Libor [Member]
Subsequent Event [Line Items]
Basis spread on variable rate (as a percent)	3.90%
SmartStop Self Storage, Inc (SmartStop) [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Purchase price per share | $ / shares		$ 13.75
Purchase price		$ 1,400,000
Cash paid		1,310,000
Remaining payments through sale of assets		$ 90,000
Number of stores acquired | Stores		122
Number of third party stores to be managed | Stores		43