Extra Space Storage (EXR) 10-Q 7 May 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	Apr. 30, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Trading Symbol	EXR
Entity Registrant Name	Extra Space Storage Inc.
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Central Index Key	0001289490
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		127,453,654

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Assets:
Real estate assets, net	$ 7,688,617	$ 7,491,831
Real estate assets - operating lease right-of-use assets	94,198	0
Investments in unconsolidated real estate ventures	161,029	125,326
Cash and cash equivalents	38,988	57,496
Restricted cash	7,840	15,194
Other assets, net	141,842	158,131
Total assets	8,132,514	7,847,978
Liabilities, Noncontrolling Interests and Equity:
Notes payable, net	4,101,958	4,137,213
Exchangeable senior notes, net	564,136	562,374
Notes payable to trusts	0	30,928
Revolving lines of credit	335,000	81,000
Operating lease liabilities	103,578	0
Cash distributions in unconsolidated real estate ventures	44,570	45,197
Accounts payable and accrued expenses	99,302	101,461
Other liabilities	110,158	104,383
Total liabilities	5,358,702	5,062,556
Commitments and contingencies
Extra Space Storage Inc. stockholders' equity:
Preferred stock, $0.01 par value, 50,000,000 shares authorized, no shares issued or outstanding	0	0
Common stock, $0.01 par value, 500,000,000 shares authorized, 127,392,050 and 127,103,750 shares issued and outstanding at March 31, 2019 and December 31, 2018, respectively	1,274	1,271
Additional paid-in capital	2,648,723	2,640,705
Accumulated other comprehensive income	11,807	34,650
Accumulated deficit	(277,655)	(262,902)
Total Extra Space Storage Inc. stockholders' equity	2,384,149	2,413,724
Noncontrolling interest represented by Preferred Operating Partnership units, net	176,264	153,096
Noncontrolling interests in Operating Partnership, net and other noncontrolling interests	213,399	218,602
Total noncontrolling interests and equity	2,773,812	2,785,422
Total liabilities, noncontrolling interests and equity	$ 8,132,514	$ 7,847,978

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, authorized (in shares)	50,000,000	50,000,000
Preferred stock, issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized (in shares)	500,000,000	500,000,000
Common stock, issued (in shares)	127,392,050	127,103,750
Common stock, outstanding (in shares)	127,392,050	127,103,750

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenues:
Property rental	$ 271,003	$ 247,886
Tenant reinsurance	29,797	27,034
Management fees and other income	10,746	10,565
Total revenues	311,546	285,485
Expenses:
Property operations	78,765	72,753
Tenant reinsurance	6,967	5,607
General and administrative	22,678	21,464
Depreciation and amortization	54,659	51,749
Total expenses	163,069	151,573
Income from operations	148,477	133,912
Interest expense	(47,360)	(40,966)
Non-cash interest expense related to amortization of discount on equity component of exchangeable senior notes	(1,162)	(1,209)
Interest income	1,388	1,438
Income before equity in earnings of unconsolidated real estate ventures and income tax expense	101,343	93,175
Equity in earnings of unconsolidated real estate ventures	2,630	3,597
Income tax expense	(1,813)	(1,342)
Net income	102,160	95,430
Net income allocated to Preferred Operating Partnership noncontrolling interests	(3,163)	(3,390)
Net income allocated to Operating Partnership and other noncontrolling interests	(4,227)	(3,784)
Net income attributable to common stockholders	$ 94,770	$ 88,256
Earnings per common share
Basic (in dollars per share)	$ 0.74	$ 0.70
Diluted (in dollars per share)	$ 0.74	$ 0.70
Weighted average number of shares
Basic (in shares)	127,037,247	125,772,439
Diluted (in shares)	134,289,716	132,682,560
Cash dividends paid per common share (in dollars per share)	$ 0.86	$ 0.78

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 102,160	$ 95,430
Other comprehensive income/(loss):
Change in fair value of interest rate swaps	(23,993)	23,063
Total comprehensive income	78,167	118,493
Less: comprehensive income attributable to noncontrolling interests	6,240	8,256
Comprehensive income attributable to common stockholders	$ 71,927	$ 110,237

Condensed Consolidated Statem_3

Condensed Consolidated Statement of Noncontrolling Interests and Equity - USD ($) $ in Thousands	Total	Redemption of Operating Partnership units for cash	Series A Preferred Operating Partnership	Series B Preferred Operating Partnership	Series C Preferred Operating Partnership	Series D Preferred Operating Partnership	Operating Partnership	Operating PartnershipRedemption of Operating Partnership units for stock	Operating PartnershipRedemption of Operating Partnership units for cash	Other	Common Stock	Common StockRedemption of Operating Partnership units for stock	Additional Paid-in Capital	Additional Paid-in CapitalRedemption of Operating Partnership units for stock	Additional Paid-in CapitalRedemption of Operating Partnership units for cash	Accumulated Other Comprehensive Income	Accumulated Deficit
Balance, beginning of period (in shares) at Dec. 31, 2017											126,007,091
Balance, beginning of period at Dec. 31, 2017	$ 2,723,807		$ 14,940	$ 41,902	$ 10,730	$ 92,064	$ 213,301			$ 119	$ 1,260		$ 2,569,485			$ 33,290	$ (253,284)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon the exercise of options (in shares)											31,525
Issuance of common stock upon the exercise of options	799												799
Restricted stock grants issued (in shares)											31,136
Restricted stock grants issued	0										$ 0		0
Restricted stock grants canceled (in shares)											(770)
Compensation expense related to stock-based awards	2,726												2,726
Repayment of receivable for preferred operating units pledged as collateral on loan	495				495
Redemption of Operating Partnership units		$ (2,558)							$ (1,126)						$ (1,432)
Noncontrolling interest in consolidated joint venture	120									120
Repurchase of equity portion of 2013 exchangeable senior notes	(21,000)												(21,000)
Net income	95,430		1,156	629	676	929	3,784										88,256
Other comprehensive income (loss)	23,063		144				938									21,981
Distributions to Operating Partnership units held by noncontrolling interests	(7,909)		(1,254)	(629)	(676)	(929)	(4,421)
Dividends paid on common stock	(98,327)																(98,327)
Balance, end of period (in shares) at Mar. 31, 2018											126,068,982
Balance, end of period at Mar. 31, 2018	$ 2,716,646		14,986	41,902	11,225	92,064	212,476			239	$ 1,260		2,550,578			55,271	(263,355)
Balance, beginning of period (in shares) at Dec. 31, 2018	127,103,750										127,103,750
Balance, beginning of period at Dec. 31, 2018	$ 2,785,422		14,756	41,902	4,374	92,064	218,362			240	$ 1,271		2,640,705			34,650	(262,902)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon the exercise of options (in shares)											169,021
Issuance of common stock upon the exercise of options	1,757												1,754
Restricted stock grants issued (in shares)											35,022
Restricted stock grants issued	0		0								$ 0
Restricted stock grants canceled (in shares)											(1,244)
Compensation expense related to stock-based awards	2,954												2,954
Redemption of Operating Partnership units (in shares)												85,501
Redemption of Operating Partnership units								$ (3,310)						$ 3,310
Issuance of Preferred D Units in the Operating Partnership in conjunction with acquisitions	23,447					23,447
Net income	102,160		1,194	629	308	1,033	4,235			(9)							94,770
Other comprehensive income (loss)	(23,993)		(147)				(1,003)									(22,843)
Distributions to Operating Partnership units held by noncontrolling interests	(8,412)		(1,326)	(629)	(308)	(1,033)	(5,116)
Dividends paid on common stock	$ (109,523)																(109,523)
Balance, end of period (in shares) at Mar. 31, 2019	127,392,050										127,392,050
Balance, end of period at Mar. 31, 2019	$ 2,773,812		$ 14,477	$ 41,902	$ 4,374	$ 115,511	$ 213,168			$ 231	$ 1,274		$ 2,648,723			$ 11,807	$ (277,655)

Condensed Consolidated Statem_4

Condensed Consolidated Statement of Noncontrolling Interests and Equity (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Stockholders' Equity [Abstract]
Dividends paid on common stock, per share (in dollars per share)	$ 0.86	$ 0.78

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Cash flows from operating activities:
Net income	$ 102,160	$ 95,430
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	54,659	51,749
Amortization of deferred financing costs	3,034	3,021
Non-cash interest expense related to amortization of discount on equity component of exchangeable senior notes	1,162	1,209
Compensation expense related to stock-based awards	2,954	2,726
Distributions from unconsolidated real estate ventures in excess of earnings	1,732	1,501
Changes in operating assets and liabilities:
Other assets	(305)	(737)
Accounts payable and accrued expenses	6,418	10,434
Other liabilities	(2,475)	6,275
Net cash provided by operating activities	169,339	171,608
Cash flows from investing activities:
Acquisition of real estate assets	(212,552)	(76,122)
Development and redevelopment of real estate assets	(15,846)	(11,106)
Proceeds from sale of real estate assets, investments in real estate ventures and other assets	0	753
Investment in unconsolidated real estate ventures	(17,395)	(438)
Return of investment in unconsolidated real estate ventures	0	47,944
Principal payments received from notes receivable	0	9,172
Purchase of equipment and fixtures	(1,182)	(1,131)
Net cash used in investing activities	(246,975)	(30,928)
Cash flows from financing activities:
Proceeds from notes payable and revolving lines of credit	424,000	162,000
Principal payments on notes payable and revolving lines of credit	(225,020)	(168,204)
Principal payments on notes payable to trusts	(30,928)	0
Deferred financing costs	(100)	(117)
Repurchase of exchangeable senior notes	0	(58,464)
Net proceeds from exercise of stock options	1,757	799
Redemption of Operating Partnership units held by noncontrolling interests	0	(2,558)
Contributions from noncontrolling interests	0	120
Dividends paid on common stock	(109,523)	(98,327)
Distributions to noncontrolling interests	(8,412)	(7,909)
Net cash provided by (used in) financing activities	51,774	(172,660)
Net decrease in cash, cash equivalents, and restricted cash	(25,862)	(31,980)
Cash, cash equivalents, and restricted cash, beginning of the period	72,690	86,044	$ 86,044
Cash, cash equivalents, and restricted cash, end of the period	46,828	54,064	$ 72,690
Supplemental schedule of cash flow information
Interest paid	45,165	37,007
Income taxes paid (received)	(177)	492
Redemption of Operating Partnership units held by noncontrolling interests for common stock
Common stock and paid-in capital	3,310	0
Establishment of operating lease right-of-use assets and lease liabilities
Real estate assets - operating lease right-of-use assets	95,506	0
Operating lease liabilities	(104,863)	0
Accounts payable and accrued expenses	9,357	0
Acquisitions of real estate assets
Real estate assets, net	223,740	70,787
Notes payable assumed	(17,157)	0
Accrued construction costs and capital expenditures
Acquisition of real estate assets	780	526
Development and redevelopment of real estate assets	0	1,381
Accounts payable and accrued expenses	(780)	(1,907)
Redemption of Operating Partnership units held by noncontrolling interests for common stock
Redemption of Operating Partnership units held by noncontrolling interests for common stock
Noncontrolling interests in Operating Partnership	(3,310)	0
Acquisitions of real estate assets
Acquisitions of real estate assets
Real estate assets, net	19,937	489
Notes payable assumed	(17,157)	0
Investment in unconsolidated real estate ventures	(2,780)	(489)
Contribution of Preferred OP Units to unconsolidated real estate venture
Contribution of Preferred OP Units to unconsolidated real estate venture
Investments in unconsolidated real estate ventures	23,447	0
Value of Preferred Operating Partnership units issued	$ (23,447)	$ 0

Organization

Organization	3 Months Ended
	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	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 was formed to continue the business of Extra Space Storage LLC and its subsidiaries, which had engaged in the self-storage business since 1977. The Company’s interest in its stores is held through its operating partnership, Extra Space Storage LP (the “Operating Partnership”), which was formed on May 5, 2004. The Company’s primary assets are general partner and limited partner interests in the Operating Partnership. This structure is commonly referred to as an umbrella partnership REIT, or UPREIT. The Company invests in stores by acquiring wholly-owned stores or by acquiring an equity interest in real estate entities. At March 31, 2019 , the Company had direct and indirect equity interests in 1,119 stores. In addition, the Company managed 577 stores for third parties, bringing the total number of stores which it owns and/or manages to 1,696 . These stores are located in 40 states, Washington, D.C. and Puerto Rico. The Company also offers tenant reinsurance at its owned and managed stores that insures the value of goods in the storage units.

Basis of Presentation

Basis of Presentation	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Basis of Presentation	BASIS OF PRESENTATION The accompanying unaudited condensed consolidated financial statements of the Company are presented on the accrual basis of accounting in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information, and in accordance with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they may not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, all adjustments (including normal recurring accruals) considered necessary for a fair presentation have been included. Operating results for the three months ended March 31, 2019 are not necessarily indicative of results that may be expected for the year ending December 31, 2019 . The condensed consolidated balance sheet as of December 31, 2018 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, 2018 , as filed with the Securities and Exchange Commission. Recently Issued Accounting Standards In February 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2016-02, “Leases (Topic 842),” which modifies the accounting for leases, intending to increase transparency and comparability of organizations by requiring balance sheet presentation of leased assets and increased financial statement disclosure of leasing arrangements. ASU 2016-02 requires entities to recognize a liability for their lease obligations and a corresponding asset representing the right to use the underlying asset over the lease term. Lease obligations are measured at their present value and accounted for using the effective interest method. The accounting for the leased asset differs slightly depending on whether the agreement is deemed to be a financing or operating lease. For financing leases, the leased asset is depreciated on a straight-line basis and is recorded separately from the interest expense in the statements of operations, resulting in higher expense in the earlier part of the lease term. For operating leases, the depreciation and interest expense components are combined, recognized evenly over the term of the lease, and presented as a reduction to operating income. ASU 2016-02 requires that assets and liabilities be presented or disclosed separately, and requires additional disclosure of certain qualitative and quantitative information related to these lease agreements. ASU 2016-02 is effective for annual and interim periods beginning after December 15, 2018. The Company adopted the standard using the modified retrospective approach as of January 1, 2019. The Company elected the package of practical expedients upon adoption, which allows for the application of the standard solely to the transition period in 2019 but does not require application to prior fiscal comparative periods presented. The Company also elected the practical expedient provided in a subsequent amendment to the standard that removed the requirement to separate lease and nonlease components. The Company did not record a significant cumulative catch-up adjustment to retained earnings upon adoption of ASU 2016-02. The primary impact was related to the Company's 21 operating ground leases and two corporate facility leases under which it serves as lessee. The Company recognized lease liabilities of $104,863 and right-of-use assets related to operating leases totaling $95,506 as of the adoption date. Refer to Note 13 for further discussion of the Company's leases. In August 2018, the FASB issued ASU 2018-15, "Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40): Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That is a Service Contract." ASU 2018-15 amends the accounting for implementation costs incurred in a hosting arrangement that is a service contract, and aligns them with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. ASU 2018-15 also requires that entities amortize the capitalized implementation costs over the term of the hosting arrangement. ASU 2018-15 is effective for annual periods beginning after December 15, 2020, with early adoption permitted, including early adoption in any interim period. The Company adopted this standard on a prospective basis as of October 1, 2018. The adoption of this standard did not have a material impact on the Company's financial statements. In June 2016, the FASB issued ASU 2016-13, "Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments." ASU 2016-13 changes how entities measure credit losses for most financial assets. This standard requires an entity to estimate its lifetime "expected credit loss" and record an allowance that, when deducted from the amortized cost basis of the financial asset, presents the net amount expected to be collected on the financial asset. The Company is evaluating the impact this new standard will have on its consolidated financial statements. In November 2018, the FASB issued ASU 2018-19, "Codification Improvements to Topic 326, Financial Instruments - Credit Losses," which clarified that receivables arising from operating leases are within the scope of the leasing standard (ASU 2016-02). This new standard will be effective for the Company on January 1, 2020. The Company is evaluating the impact this new standard will have on its consolidated financial statements.

Fair Value Disclosures

Fair Value Disclosures	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value Disclosures	FAIR VALUE DISCLOSURES Derivative Financial Instruments Currently, the Company uses interest rate swaps to manage its interest rate risk. The valuation of these instruments is determined using widely accepted valuation techniques, including discounted cash flow analysis on the expected cash flows of each derivative. This analysis reflects the contractual terms of the derivatives, including the period to maturity, and uses observable market-based inputs, including interest rate curves. The fair values of interest rate swaps are determined using the market standard methodology of netting the discounted future fixed cash payments and the discounted expected variable cash receipts. The variable cash receipts are based on an expectation of future interest rates (forward curves) derived from observable market interest rate forward curves. The Company incorporates credit valuation adjustments to appropriately reflect both its own nonperformance risk and the respective counterparty’s nonperformance risk in the fair value measurements. In adjusting the fair value of its derivative contracts for the effect of nonperformance risk, the Company has considered the impact of netting and any applicable credit enhancements, such as collateral postings, thresholds, mutual puts and guarantees. In conjunction with the FASB’s fair value measurement guidance, the Company made an accounting policy election to measure the credit risk of its derivative financial instruments that are subject to master netting agreements on a net basis by counterparty portfolio. Although the Company has determined that the majority of the inputs used to value its derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with its derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default by the Company and its counterparties. However, as of March 31, 2019 , the Company 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 has determined that its derivative valuations in their entirety were classified in Level 2 of the fair value hierarchy. The table below presents the Company’s assets and liabilities measured at fair value on a recurring basis as of March 31, 2019 , aggregated by the level in the fair value hierarchy within which those measurements fall. Fair Value Measurements at Reporting Date Using Description 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 $ — $ 25,908 $ — Other liabilities - cash flow hedge swap agreements $ — $ 9,307 $ — The Company did not have any significant assets or liabilities that are re-measured on a recurring basis using significant unobservable inputs as of March 31, 2019 or December 31, 2018 . Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis Long-lived assets held for use are evaluated for impairment when events or circumstances indicate there may be impairment. The Company reviews each store at least annually to determine if any such events or circumstances have occurred or exist. The Company focuses on stores where occupancy and/or rental income have decreased by a significant amount. For these stores, the Company determines whether the decrease is temporary or permanent, and whether the store will likely recover the lost occupancy and/or revenue in the short term. In addition, the Company reviews stores in the lease-up stage and compares actual operating results to original projections. When the Company determines that an event that may indicate impairment has occurred, the Company compares the carrying value of the related long-lived assets to the undiscounted future net operating cash flows attributable to the assets. An impairment loss is recorded if the net carrying value of the assets exceeds the undiscounted future net operating cash flows attributable to the assets. The impairment loss recognized equals the excess of net carrying value over the related fair value of the assets. When real estate assets are identified by management as held for sale, the Company discontinues depreciating the assets and estimates the fair value of the assets, net of selling costs. If the estimated fair value, net of selling costs, of the assets that have been identified as held for sale is less than the net carrying value of the assets, the Company would recognize an impairment loss on the assets held for sale. The operations of assets held for sale or sold during the period are presented as part of normal operations for all periods presented. As of March 31, 2019 , the Company had one operating store classified as held for sale and one parcel of land classified as held for sale which are included in real estate assets, net. The estimated fair value less selling costs for each of these assets is greater than the carrying value of the assets, and therefore no loss has been recorded. The Company assesses annually whether there are any indicators that the value of the Company’s investments in unconsolidated real estate ventures may be impaired 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 relative fair values, which are estimated using significant unobservable inputs. The value of the tangible assets, consisting of land and buildings, is determined as if vacant. Intangible assets, which represent the value of existing tenant relationships, are recorded at their fair values based on the avoided cost to replace the current leases. The Company measures the value of tenant relationships based on the rent lost due to the amount of time required to replace existing customers, which is based on the Company’s historical experience with turnover in its stores. Any debt assumed as part of an acquisition is recorded at fair value based on current interest rates compared to contractual rates. Acquisition-related transaction costs are capitalized as part of the purchase price. Fair Value of Financial Instruments The carrying values of cash and cash equivalents, restricted cash, receivables, other financial instruments included in other assets, accounts payable and accrued expenses, variable-rate notes payable, lines of credit and other liabilities reflected in the condensed consolidated balance sheets at March 31, 2019 and December 31, 2018 approximate fair value. Restricted cash is comprised of letters of credit and escrowed funds deposited with financial institutions located throughout the United States relating to earnest money deposits on potential acquisitions, real estate taxes, insurance and capital expenditures. The fair values of the Company’s notes receivable from Preferred Operating Partnership unit holders and other fixed rate notes receivable, which are recorded in other assets, net were based on the discounted estimated future cash flows of the notes (categorized within Level 3 of the fair value hierarchy); the discount rate used approximated the current market rate for loans with similar maturities and credit quality. The fair values of the Company’s fixed-rate notes payable and notes payable to trusts were estimated using the discounted estimated future cash payments to be made on such debt (categorized within Level 3 of the fair value hierarchy); the discount rates used approximated current market rates for loans, or groups of loans, with similar maturities and credit quality. The fair value of the Company’s exchangeable senior notes was estimated using an average market price for similar securities obtained from a third party. The fair values of the Company’s fixed-rate assets and liabilities were as follows for the periods indicated: March 31, 2019 December 31, 2018 Fair Carrying Fair Carrying Notes receivable from Preferred and Common Operating Partnership unit holders $ 116,957 $ 119,735 $ 115,467 $ 119,735 Fixed rate notes payable and notes payable to trusts $ 3,057,072 $ 3,051,171 $ 2,985,731 $ 3,022,414 Exchangeable senior notes $ 660,894 $ 575,000 $ 620,149 $ 575,000

Earnings Per Common Share

Earnings Per Common Share	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Earnings Per Common Share	EARNINGS PER COMMON SHARE Basic earnings per common share is computed using the two-class method by dividing net income attributable to common stockholders by the weighted average number of common shares outstanding during the period. All outstanding unvested restricted stock awards contain rights to non-forfeitable dividends and participate in undistributed earnings with common stockholders; accordingly, they are considered participating securities that are included in the two-class method. Diluted earnings per common share measures the performance of the Company over the reporting period while giving effect to all potential common shares that were dilutive and outstanding during the period. The denominator includes the weighted average number of basic shares and the number of additional common shares that would have been outstanding if the potential common shares that were dilutive had been issued, and is calculated using either the two-class, treasury stock or as if-converted method, whichever is most dilutive. Potential common shares are securities (such as options, convertible debt, Series A Participating Redeemable Preferred Units (“Series A Units”), Series B Redeemable Preferred Units (“Series B Units”), Series C Convertible Redeemable Preferred Units (“Series C Units”), Series D Redeemable Preferred Units (“Series D Units” and, together with the Series A Units, Series B Units and Series C Units, the “Preferred OP Units”) and common Operating Partnership units (“OP Units”)) that do not have a current right to participate in earnings of the Company but could do so in the future by virtue of their option, redemption or conversion right. In computing the dilutive effect of convertible securities, net income is adjusted to add back any changes in earnings in the period associated with the convertible security. The numerator also is adjusted for the effects of any other non-discretionary changes in income or loss that would result from the assumed conversion of those potential common shares. In computing diluted earnings per common share, only potential common shares that are dilutive (i.e. those that reduce earnings per common share) are included. For the three months ended March 31, 2019 , there were no anti-dilutive options. For the three months ended March 31, 2018 , options to purchase an aggregate of approximately 40,956 shares of common stock were excluded from the computation of earnings per share as their effect would have been anti-dilutive. For the purposes of computing the diluted impact of the potential exchange of the Preferred Operating Partnership units for common shares upon redemption, where the Company has the option to redeem in cash or shares and where the Company has stated the intent and ability to settle the redemption in shares, the Company divided the total value of the Preferred Operating Partnership units by the average share price for the period presented. The average share price for the three months ended March 31, 2019 and 2018 was $96.05 and $84.11 , respectively. 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. For the Three Months Ended March 31, 2019 2018 Equivalent Shares (if converted) Equivalent Shares (if converted) Series B Units 436,254 498,183 Series C Units 129,763 352,385 Series D Units 1,083,265 1,094,555 1,649,282 1,945,123 The Operating Partnership had no amounts issued and outstanding of its 2.375% Exchangeable Senior Notes due 2033 (the “2013 Notes”) as of March 31, 2019 , as the remaining principal balance had been redeemed in July 2018. Prior to their redemption, the 2013 Notes could potentially have had a dilutive impact on the Company’s earnings per share calculations. The 2013 Notes were 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 Company had irrevocably agreed to pay only cash for the accreted principal amount of the 2013 Notes relative to its exchange obligations, but retained the right to satisfy the exchange obligation in excess of the accreted principal amount in cash and/or common stock. The Operating Partnership had $575,000 of its 3.125% Exchangeable Senior Notes due 2035 (the “2015 Notes”) issued and outstanding as of March 31, 2019 . The 2015 Notes could potentially have a dilutive impact on the Company’s earnings per share calculations. The 2015 Notes are exchangeable by holders into shares of the Company’s common stock under certain circumstances per the terms of the indenture governing the 2015 Notes. The exchange price of the 2015 Notes was $92.55 per share as of March 31, 2019 , and could change over time as described in the indenture. The Company has irrevocably agreed to pay only cash for the accreted principal amount of the 2015 Notes relative to its exchange obligations, but retained the right to satisfy the exchange obligation in excess of the accreted principal amount in cash and/or common stock. Although the Company has retained the right to satisfy the exchange obligation in excess of the accreted principal amount of the 2013 Notes and 2015 Notes in cash and/or common stock, Accounting Standards Codification (“ASC”) 260, “Earnings per Share,” requires an assumption that shares would be used to pay the exchange obligation in excess of the accreted principal amount, and requires that those shares be included in the Company’s calculation of weighted average common shares outstanding for the diluted earnings per share computation. For the three months ended March 31, 2019 and 2018 , zero and 81,382 shares, respectively, related to the 2013 Notes were included in the computation for diluted earnings per share. For the three months ended March 31, 2019 and 2018 , 226,527 and zero shares, respectively, related to the 2015 Notes were included in the computation for diluted earnings per share. The exchange price exceeded the average per share price of the Company’s common stock during the three months ended March 31, 2018 . For the purposes of computing the diluted impact on earnings per share of the potential exchange of Series A Units for common shares upon redemption, where the Company has the option to redeem in cash or shares and where the Company has stated the positive intent and ability to settle at least $101,700 of the instrument in cash (or net settle a portion of the Series A Units against the related outstanding note receivable), only the amount of the instrument in excess of $101,700 is considered in the calculation of shares contingently issuable for the purposes of computing diluted earnings per share as allowed by ASC 260-10-45-46. Accordingly, the number of shares included in the computation for diluted earnings per share related to the Series A Units is equal to the number of Series A Units outstanding, with no additional shares included related to the fixed $101,700 amount. The computation of earnings per common share is as follows for the periods presented: For the Three Months Ended March 31, 2019 2018 Net income attributable to common stockholders $ 94,770 $ 88,256 Earnings and dividends allocated to participating securities (167 ) (178 ) Earnings for basic computations 94,603 88,078 Earnings and dividends allocated to participating securities — 178 Income allocated to noncontrolling interest - Preferred Operating Partnership Units and Operating Partnership Units 5,429 4,941 Fixed component of income allocated to noncontrolling interest - Preferred Operating Partnership (Series A Units) (572 ) (572 ) Net income for diluted computations $ 99,460 $ 92,625 Weighted average common shares outstanding: Average number of common shares outstanding - basic 127,037,247 125,772,439 OP Units 5,960,981 5,663,370 Series A Units 875,480 875,480 Shares related to exchangeable senior notes and dilutive stock options 416,008 371,271 Average number of common shares outstanding - diluted 134,289,716 132,682,560 Earnings per common share Basic $ 0.74 $ 0.70 Diluted $ 0.74 $ 0.70

Store Acquisitions and Disposit

Store Acquisitions and Dispositions	3 Months Ended
	Mar. 31, 2019
Real Estate [Abstract]
Store Acquisitions and Dispositions	STORE ACQUISITIONS AND DISPOSITIONS The following table shows the Company’s acquisitions of stores for the three months ended March 31, 2019 and 2018 . The table excludes purchases of raw land and improvements made to existing assets. All acquisitions are considered asset acquisitions under ASU 2017-01, " Business Combinations (Topic 805): Clarifying the Definition of a Business ." Consideration Paid Total Quarter Number of Stores Total Cash Paid Loan Assumed Investments in Real Estate Ventures Net Liabilities/ (Assets) Assumed Real estate assets Q1 2019 14 (1) $ 223,740 $ 202,890 $ 17,157 $ 2,780 $ 913 $ 223,740 Q1 2018 5 (2) $ 70,787 $ 70,171 $ — $ 489 $ 127 $ 70,787 (1) Store acquisitions during the three months ended March 31, 2019 include the purchase of 12 stores previously held in joint ventures where the Company held a noncontrolling interest. The Company purchased its partners' remaining equity interests in the joint ventures, and the properties owned by the joint ventures became wholly owned by the Company. No gain or loss was recognized as a result of this acquisition. (2) Store acquisitions during the three months ended March 31, 2018 include the acquisition of one store that had been owned by a joint venture in which the Company held a noncontrolling interest. No gain or loss was recognized as a result of this acquisition.

Investments in Unconsolidated R

Investments in Unconsolidated Real Estate Ventures	3 Months Ended
	Mar. 31, 2019
Equity Method Investments and Joint Ventures [Abstract]
Investments in Unconsolidated Real Estate Ventures	INVESTMENTS IN UNCONSOLIDATED REAL ESTATE VENTURES Investments in unconsolidated real estate ventures represent the Company's noncontrolling interests in properties. The Company accounts for these investments using the equity method of accounting. The Company initially records these investments at cost and subsequently adjusts for cash contributions, distributions and net equity in income or loss, which is allocated in accordance with the provisions of the applicable partnership or joint venture agreement. In these joint ventures, the Company and the joint venture partner generally receive a preferred return on their invested capital. To the extent that cash or profits in excess of these preferred returns are generated through operations or capital transactions, the Company would receive a higher percentage of the excess cash or profits than its equity interest. The Company separately reports investments with net equity less than zero in cash distributions in unconsolidated real estate ventures in the condensed consolidated balance sheets. The net equity of certain joint ventures is less than zero because distributions have exceeded the Company's investment in and share of income from these joint ventures. This is generally the result of financing distributions, capital events or operating distributions that are usually greater than net income, as net income includes non‑cash charges for depreciation and amortization while distributions do not. During the three months ended March 31, 2019 , the Company contributed a total of $40,843 to its joint ventures for the purchase of one operating store and six stores acquired at the issuance of certificate of occupancy. Net investments in unconsolidated real estate ventures and cash distributions in unconsolidated real estate ventures consist of the following: Number of Stores Equity Ownership % Excess Profit % (1) March 31, December 31, 2019 2018 PRISA Self Storage LLC 85 4% 4% $ 9,292 $ 9,334 Storage Portfolio II JV LLC 36 10% 30% (4,539 ) (4,233 ) Storage Portfolio I LLC 24 34% 49% (38,186 ) (38,129 ) VRS Self Storage, LLC 16 45% 54% 18,002 18,281 Extra Space Northern Properties Six LLC 10 10% 35% (1,793 ) (1,700 ) WICNN JV LLC 9 10% 25% 32,859 26,885 Alan Jathoo JV LLC 9 10% 10% 8,132 8,180 ESS Bristol Investments LLC 8 10% 28% 3,025 2,331 GFN JV, LLC 5 10% 25% 12,429 10,586 Extra Space West Two LLC — 5% 40% — (2 ) 3,818 Extra Space West One LLC — 5% 40% — (2 ) (1,038 ) Other minority owned stores 22 10-50% 19-50% 77,238 45,814 Net Investments in and Cash distributions in unconsolidated real estate ventures 224 $ 116,459 $ 80,129 (1) Includes pro-rata equity ownership share and promoted interest. (2) In January 2019, the Company purchased its joint venture partners' 95% interests in the Extra Space West One LLC and Extra Space West Two LLC joint ventures, which owned a total of 12 stores. The Company paid $172,505 of cash to acquire the equity interests, and subsequent to this acquisition, the Company owned 100% of the joint ventures and the related stores. On February 2, 2018, the Company and Teachers REA II LLC ("TIAA") entered into the Third Amendment to Amended and Restated Limited Liability Company Agreement of Storage Portfolio I LLC (the "Amendment"). The Amendment was deemed effective as of January 1, 2018. Under the Amendment, the Company's capital percentage in Storage Portfolio I LLC ("SP I") increased from 25.0% to 34.0% , and its excess profit participation percentage increased from 40.0% to 49.0% , among other changes. Additionally, SP I refinanced its mortgage loan and the Company received a financing distribution of $47,944 , which was recorded as a reduction in the Company's investment in SP I. The Company continues to account for its investment in SP I under the equity method of accounting.

Variable Interests

Variable Interests	3 Months Ended
	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Variable Interests	VARIABLE INTERESTS The Operating Partnership had three wholly-owned unconsolidated subsidiaries (“Trust,” “Trust II” and “Trust III,” together, the “Trusts”) that had 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 were variable interest entities ("VIEs") because the holders of the equity investment at risk (the trust preferred securities) did 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 was not considered an equity investment at risk. The Operating Partnership’s investment in the Trusts was 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 was not the primary beneficiary of the Trusts, they were not consolidated. A debt obligation was recorded in the form of notes for the proceeds as discussed above, which were owed to the Trusts. The Company had also included its investment in the Trusts’ common securities in other assets on the condensed consolidated balance sheets. During the year ended December 31, 2018, the Company repaid a total principal amount of $88,662 , representing all of the notes payable to Trust III, all of the notes payable to Trust II, and all but $30,928 of the notes payable to Trust. The Trusts used the proceeds from these repayments to redeem their preferred and common securities. During the three months ended March 31, 2019 , the Company repaid the remaining balance of $30,928 of notes payable to Trust. During the time they were outstanding, the Company did not provide 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 was 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 was equal to the notes payable that the Trusts owed to third parties for their investments in the Trusts’ preferred securities. The Company had no consolidated VIEs during the three months ended March 31, 2019 .

Derivatives

Derivatives	3 Months Ended
	Mar. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives	DERIVATIVES The Company is exposed to certain risks arising from both its business operations and economic conditions. The Company principally manages its exposures to a wide variety of business and operational risks through management of its core business activities. The Company manages economic risks, including interest rate, liquidity and credit risk, primarily by managing the amount, sources and duration of its debt funding and by using derivative financial instruments. Specifically, the Company enters into derivative financial instruments to manage exposure that arises from business activities that result in the receipt or payment of future known and uncertain cash amounts, the value of which are determined by interest rates. The Company’s derivative financial instruments are used to manage differences in the amount, timing and duration of the Company’s known or expected cash receipts and its known or expected cash payments principally related to the Company’s investments and borrowings. Cash Flow Hedges of Interest Rate Risk The Company’s objectives in using interest rate derivatives are to add stability to interest expense and to manage its exposure to interest rate movements. To accomplish these objectives, the Company primarily uses interest rate swaps as part of its interest rate risk management strategy. Interest rate swaps designated as cash flow hedges involve the receipt of variable amounts from a counterparty in exchange for the Company making fixed-rate payments over the life of the agreements without exchange of the underlying notional amount. The effective portion of changes in the fair value of derivatives designated and that qualify as cash flow hedges is recorded in accumulated other comprehensive income (“OCI”) and is subsequently reclassified into earnings in the period that the hedged forecasted transaction affects earnings. A portion of these changes is excluded from accumulated other comprehensive income as it is allocated to noncontrolling interests. During the three months ended March 31, 2019 and 2018 , such derivatives were used to hedge the variable cash flows associated with existing variable-rate debt. In the coming 12 months, the Company estimates that $13,649 will be reclassified and reduce interest expense. The Company held 28 derivative financial instruments which had a total combined notional amount of $2,287,824 as of March 31, 2019 . Fair Values of Derivative Instruments The table below presents the fair value of the Company’s derivative financial instruments as well as their classification on the condensed consolidated balance sheets: Asset / Liability Derivatives March 31, 2019 December 31, 2018 Derivatives designated as hedging instruments: Fair Value Other assets $ 25,908 $ 42,324 Other liabilities $ 9,307 $ 2,131 Effect of Derivative Instruments The table below presents 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: Gain (loss) recognized in OCI For the Three Months Ended March 31, Location of amounts reclassified from OCI into income Gain reclassified from OCI For the Three Months Ended March 31, Type 2019 2018 2019 2018 Swap Agreements $ (19,576 ) $ 23,317 Interest expense $ 4,462 $ 240 Credit-risk-related Contingent Features The Company has agreements with some of its derivative counterparties that contain provisions pursuant to which the Company could be declared in default of its derivative obligations if the Company defaults on any of its indebtedness, including default where repayment of the indebtedness has not been accelerated by the lender. The Company also has an agreement with some of its derivative counterparties that incorporates the loan covenant provisions of the Company’s indebtedness with a lender affiliate of the derivative counterparty. Failure to comply with the loan covenant provisions would result in the Company being in default on any derivative instrument obligations covered by the agreement. As of March 31, 2019 , the fair value of derivatives in a net liability position, which includes accrued interest but excludes any adjustment for nonperformance risk, related to these agreements was $9,889 . As of March 31, 2019 , the Company had not posted any collateral related to these agreements. If the Company had breached any of these provisions as of March 31, 2019 , it could have been required to cash settle its obligations under the agreements at their termination value of $9,889 , including accrued interest.

Exchangeable Senior Notes

Exchangeable Senior Notes	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Exchangeable Senior Notes	EXCHANGEABLE SENIOR NOTES In September 2015, the Operating Partnership issued $575,000 of its 3.125% Exchangeable Senior Notes due 2035. Costs incurred to issue the 2015 Notes were approximately $11,992 , consisting primarily of a 2.0% underwriting fee. These costs are being amortized as an adjustment to interest expense over five years , which represents the estimated term based on the first available redemption date, and are included in exchangeable senior notes, net, in the 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 2015 Notes bear interest at 3.125% per annum and contain an exchange settlement feature, which provides that the 2015 Notes may, under certain circumstances, be exchangeable for cash (for the principal amount of the 2015 Notes) and, with respect to any excess exchange value, for cash, shares of the Company’s common stock, or a combination of cash and shares of the Company’s common stock, at the Company’s option. The exchange rate of the 2015 Notes as of March 31, 2019 was approximately 10.81 shares of the Company’s common stock per $1,000 principal amount of the 2015 Notes. The Operating Partnership may redeem the 2015 Notes at any time to preserve the Company’s status as a REIT. In addition, on or after October 5, 2020, the Operating Partnership may redeem the 2015 Notes for cash, in whole or in part, at 100% of the principal amount plus accrued and unpaid interest, upon at least 30 days but not more than 60 days prior written notice to the holders of the 2015 Notes. The holders of the 2015 Notes have the right to require the Operating Partnership to repurchase the 2015 Notes for cash, in whole or in part, on October 1 of the years 2020, 2025 and 2030 (unless the Operating Partnership has called the 2015 Notes for redemption), and upon the occurrence of certain designated events, in each case for a repurchase price equal to 100% of the principal amount of the 2015 Notes plus accrued and unpaid interest. Certain events are considered “Events of Default,” as defined in the indenture governing the 2015 Notes, which may result in the accelerated maturity of the 2015 Notes. Additionally, the 2015 Notes can be exchanged during any calendar quarter, if the last reported sale price of the common stock of the Company is greater than or equal to 130% of the exchange price for at least 20 trading days during a period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter. The price of the Company’s common stock did not exceed 130% of the exchange price for the required time period for the 2015 Notes during the quarter ended March 31, 2019 . 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 , and costs incurred to issue the 2013 Notes were approximately $1,672 . These costs were amortized as an adjustment to interest expense over five years , which represented the estimated term based on the first available redemption date. The 2013 Notes bore interest at 2.375% per annum and contained an exchange settlement feature. During the three months ended March 31, 2018, the Company repurchased a total principal amount of $37,704 of the 2013 Notes. The Company paid cash of $58,464 for the total of the principal amount and the exchange value in excess of the principal amount. The Operating Partnership redeemed all remaining outstanding 2013 Notes on July 5, 2018. GAAP requires entities with convertible debt instruments that may be settled entirely or partially in cash upon conversion to separately account for the liability and equity components of the instrument in a manner that reflects the issuer’s economic interest cost. The Company therefore accounts for the liability and equity 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 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 the 2013 Notes and the 2015 Notes is 4.0% , which approximated 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 2015 Notes, including the total carrying amount of the equity component, the principal amount of the liability component, the unamortized discount and the net carrying amount was as follows for the periods indicated: March 31, 2019 December 31, 2018 Carrying amount of equity component $ 22,597 $ 22,597 Principal amount of liability component $ 575,000 $ 575,000 Unamortized discount - equity component (7,255 ) (8,417 ) Unamortized debt issuance costs (3,609 ) (4,209 ) Net carrying amount of liability components $ 564,136 $ 562,374 The amount of interest cost recognized relating to the contractual interest rate and the amortization of the discount on the liability component of the 2015 Notes were as follows for the periods indicated: For the Three Months Ended March 31, 2019 2018 Contractual interest $ 4,492 $ 4,561 Amortization of discount 1,162 1,209 Total interest expense recognized $ 5,654 $ 5,770

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2019
Stockholders' Equity Note [Abstract]
Stockholders' Equity	STOCKHOLDERS’ EQUITY On May 6, 2016, the Company filed its $400,000 "at the market" equity program with the Securities and Exchange Commission using a shelf registration statement on Form S-3, and entered into separate equity distribution agreements with five sales agents. During the three months ended March 31, 2019 , the Company did no t issue any shares and had $257,929 available for issuance under the equity distribution agreements.

Noncontrolling Interest Represe

Noncontrolling Interest Represented by Preferred Operating Partnership Units	3 Months Ended
	Mar. 31, 2019
Noncontrolling Interest [Abstract]
Noncontrolling Interest Represented by Preferred Operating Partnership Units	NONCONTROLLING INTEREST REPRESENTED BY PREFERRED OPERATING PARTNERSHIP UNITS Classification of Noncontrolling Interests GAAP requires a company to present ownership interests in subsidiaries held by parties other than the company in the consolidated financial statements within the equity section, but separate from the company’s equity. It also requires the amount of consolidated net income attributable to the parent and to the noncontrolling interest to be clearly identified and presented on the face of the consolidated statement of operations and requires changes in ownership interest to be accounted for similarly as equity transactions. If noncontrolling interests are determined to be redeemable, they are to be carried at their redemption value as of the balance sheet date and reported as temporary equity. The Company has evaluated the terms of the Operating Partnership’s preferred units and classifies the noncontrolling interest represented by such preferred units as stockholders’ equity in the accompanying 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. At March 31, 2019 and December 31, 2018 , the noncontrolling interests represented by the Preferred OP Units qualified for classification as permanent equity on the Company's condensed consolidated balance sheets. The partnership agreement of the Operating Partnership (as amended, the "Partnership Agreement") provides for the designation and issuance of the OP Units. Noncontrolling interests in Preferred OP Units were presented net of notes receivable from preferred OP unit holders of $108,644 as of March 31, 2019 and December 31, 2018 , as more fully described below. Series A Participating Redeemable Preferred Units The Partnership Agreement provides for the designation and issuance of the Series A Units. The Series A Units have priority over all other partnership interests of the Operating Partnership with respect to distributions and liquidation. The Series A Units were issued in June 2007. Series A Units in the amount of $101,700 bear a fixed priority return of 2.3% and originally had a fixed liquidation value of $115,000 . The remaining balance participates in distributions with, and has a liquidation value equal to that of the 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. As a result of the redemption of 114,500 Series A Units in October 2014, the remaining fixed liquidation value was reduced to $101,700 , which represents 875,480 Series A Units. On April 18, 2017, the holder of the Series A Units and the Operating Partnership agreed to reduce the fixed priority return on the Series A Units from 5.0% to 2.3% in exchange for a reduction in the interest rate of the related loan, as more fully described below. On June 25, 2007, the Operating Partnership loaned the holder of the Series A Units $100,000 . On April 18, 2017, a loan amendment was signed modifying the maturity date of the loan to the later of the death of the Series A Unit holder or his spouse and also lowering the interest rate of the loan from 4.9% to 2.1% . The loan amendment was determined to be a loan modification under GAAP, and therefore no change in value was recognized. The loan is secured by the borrower’s Series A Units. No future redemption of Series A Units can be made unless the loan secured by the Series A Units is also repaid. The Series A Units are shown on the balance sheet net of the $100,000 loan because the borrower under the loan receivable is also the holder of the Series A Units. Series B Redeemable Preferred Units The Partnership Agreement provides for the designation and issuance of the Series B Units. The Series B Units rank junior to the Series A Units, on parity with the Series C Units and Series D Units, and senior to all other partnership interests of the Operating Partnership with respect to distributions and liquidation. The Series B Units were issued in 2013 and 2014 and have a liquidation value of $25.00 per unit for a fixed liquidation value of $41,902 , which represents 1,676,087 Series B Units. Holders of the Series B Units receive distributions at an annual rate of 6.0% . These distributions are cumulative. The Series B Units became redeemable at the option of the holder on the first anniversary of the date of issuance, which redemption obligation may be satisfied at the Company’s option in cash or shares of its common stock. Series C Convertible Redeemable Preferred Units The Partnership Agreement provides for the designation and issuance of the Series C Units. The Series C Units rank junior to the Series A Units, on parity with the Series B Units and Series D Units, and senior to all other partnership interests of the Operating Partnership with respect to distributions and liquidation. The Series C Units were issued in 2013 and 2014 and have a liquidation value of $42.10 per unit for a fixed liquidation value of $12,462 , which represents 296,020 Series C Units. From issuance to the fifth anniversary of issuance, each Series C Unit holder will receive quarterly distributions equal to the quarterly distribution per OP Unit plus $0.18 . Beginning on the fifth anniversary of issuance, each Series C Unit holder will receive a fixed quarterly distribution equal to the aggregate quarterly distribution payable in respect of such Series C Unit during the four quarters immediately preceding the fifth anniversary of issuance, divided by four. These distributions are cumulative. The Series C Units became redeemable at the option of the holder one year from the date of issuance, which redemption obligation may be satisfied at the Company’s option in cash or shares of its common stock. The Series C Units are convertible into OP Units at the option of the holder 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 loan receivable, which was collateralized by the Series C Units, bears interest at 5.0% per annum and matures on December 15, 2024 . The Series C Units are shown on the balance sheet net of the loan balance because the borrower under the loan receivable is also the holder of the Series C Units. On December 1, 2018, certain holders of the Series C Units converted their Series C Units into OP Units, with a total of 407,996 Series C Units being converted into a total of 373,113 OP Units. As part of this conversion, the holders of the Series C Units agreed to pledge the OP Units received in the conversion as collateral on the loan receivable to replace the Series C Units that were converted. As of March 31, 2019 and December 31, 2018, the total outstanding balance of the loan receivable was $19,735 , of which $8,644 is shown as a reduction of the noncontrolling interests related to the Series C Units and $11,091 is shown as a reduction of the noncontrolling interests related to the OP Units on the Company's consolidated balance sheets. On April 25, 2019, subsequent to quarter-end, the remaining 296,020 Series C Units were converted into 270,710 OP Units. Series D Redeemable Preferred Units The Partnership Agreement provides for the designation and issuance of the Series D Units. The Series D Units rank junior to the Series A Units, on parity with the Series B Units and Series C Units, and senior to all other partnership interests of the Operating Partnership with respect to distributions and liquidation. The Series D Units have been issued at various times from 2014 to 2017. In addition, during the three months ended March 31, 2019 , the Operating Partnership issued 937,924 Series D Units valued at $23,447 in conjunction with joint venture acquisitions. The Series D Units have a liquidation value of $25.00 per unit, for a fixed liquidation value of $115,511 , which represents 4,620,445 Series D Units. Holders of the Series D Units receive distributions at an annual rate between 3.0% and 5.0% . These distributions are cumulative. The Series D Units become redeemable at the option of the holder on the first anniversary of the date of issuance, which redemption obligation may be satisfied at the Company’s option in cash or shares of its common stock. In addition, certain of the Series D Units are exchangeable for OP Units at the option of the holder until the tenth anniversary of the date of issuance, with the number of OP Units to be issued equal to $25.00 per Series D Unit, divided by the value of a share of common stock as of the exchange date. NONCONTROLLING INTEREST IN OPERATING PARTNERSHIP AND OTHER NONCONTROLLING INTERESTS Noncontrolling Interest in Operating Partnership The Company’s interest in its stores is held through the Operating Partnership. Between its general partner and limited partner interests, the Company held a 90.5% ownership interest in the Operating Partnership as of March 31, 2019 . The remaining ownership interests in the Operating Partnership (including Preferred OP Units) of 9.5% are held by certain former owners of assets acquired by the Operating Partnership. The noncontrolling interest in the Operating Partnership represents OP Units that are not owned by the Company. OP Units are redeemable at the option of the holder, which redemption may be satisfied at the Company's option in cash, based upon the fair market value of an equivalent number of shares of the Company’s common stock (based on the ten -day average trading price) at the time of the redemption, or shares of the Company's common stock on a one-for-one basis , subject to anti-dilution adjustments provided in the Partnership Agreement. As of March 31, 2019 , the ten -day average closing price of the Company's common stock was $100.76 and there were 5,908,750 OP Units outstanding. Assuming that all of the OP Unit holders exercised their right to redeem all of their OP Units on March 31, 2019 and the Company elected to pay the OP Unit holders cash, the Company would have paid $595,366 in cash consideration to redeem the units. OP Unit activity is summarized as follows for the periods presented: For the Three Months Ended March 31, 2019 2018 OP Units redeemed for common stock 85,501 — OP Units redeemed for cash — 30,000 Cash paid for OP Units redeemed $ — $ 2,558 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. Other Noncontrolling Interests Other noncontrolling interests represent the ownership interests of third parties in two consolidated joint ventures as of March 31, 2019 . One joint venture owns two operating stores in Texas, an operating store and a development store in Colorado, and the other joint venture owns one operating store in Pennsylvania and one development property in New Jersey. The voting interests of the third-party owners are between 5.0% and 20.0% .

Noncontrolling Interest in Oper

Noncontrolling Interest in Operating Partnership and Other Noncontrolling Interests	3 Months Ended
	Mar. 31, 2019
Noncontrolling Interest [Abstract]
Noncontrolling Interest in Operating Partnership and Other Noncontrolling Interests	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. At March 31, 2019 and December 31, 2018 , the noncontrolling interests represented by the Preferred OP Units qualified for classification as permanent equity on the Company's condensed consolidated balance sheets. The partnership agreement of the Operating Partnership (as amended, the "Partnership Agreement") provides for the designation and issuance of the OP Units. Noncontrolling interests in Preferred OP Units were presented net of notes receivable from preferred OP unit holders of $108,644 as of March 31, 2019 and December 31, 2018 , as more fully described below. Series A Participating Redeemable Preferred Units The Partnership Agreement provides for the designation and issuance of the Series A Units. The Series A Units have priority over all other partnership interests of the Operating Partnership with respect to distributions and liquidation. The Series A Units were issued in June 2007. Series A Units in the amount of $101,700 bear a fixed priority return of 2.3% and originally had a fixed liquidation value of $115,000 . The remaining balance participates in distributions with, and has a liquidation value equal to that of the 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. As a result of the redemption of 114,500 Series A Units in October 2014, the remaining fixed liquidation value was reduced to $101,700 , which represents 875,480 Series A Units. On April 18, 2017, the holder of the Series A Units and the Operating Partnership agreed to reduce the fixed priority return on the Series A Units from 5.0% to 2.3% in exchange for a reduction in the interest rate of the related loan, as more fully described below. On June 25, 2007, the Operating Partnership loaned the holder of the Series A Units $100,000 . On April 18, 2017, a loan amendment was signed modifying the maturity date of the loan to the later of the death of the Series A Unit holder or his spouse and also lowering the interest rate of the loan from 4.9% to 2.1% . The loan amendment was determined to be a loan modification under GAAP, and therefore no change in value was recognized. The loan is secured by the borrower’s Series A Units. No future redemption of Series A Units can be made unless the loan secured by the Series A Units is also repaid. The Series A Units are shown on the balance sheet net of the $100,000 loan because the borrower under the loan receivable is also the holder of the Series A Units. Series B Redeemable Preferred Units The Partnership Agreement provides for the designation and issuance of the Series B Units. The Series B Units rank junior to the Series A Units, on parity with the Series C Units and Series D Units, and senior to all other partnership interests of the Operating Partnership with respect to distributions and liquidation. The Series B Units were issued in 2013 and 2014 and have a liquidation value of $25.00 per unit for a fixed liquidation value of $41,902 , which represents 1,676,087 Series B Units. Holders of the Series B Units receive distributions at an annual rate of 6.0% . These distributions are cumulative. The Series B Units became redeemable at the option of the holder on the first anniversary of the date of issuance, which redemption obligation may be satisfied at the Company’s option in cash or shares of its common stock. Series C Convertible Redeemable Preferred Units The Partnership Agreement provides for the designation and issuance of the Series C Units. The Series C Units rank junior to the Series A Units, on parity with the Series B Units and Series D Units, and senior to all other partnership interests of the Operating Partnership with respect to distributions and liquidation. The Series C Units were issued in 2013 and 2014 and have a liquidation value of $42.10 per unit for a fixed liquidation value of $12,462 , which represents 296,020 Series C Units. From issuance to the fifth anniversary of issuance, each Series C Unit holder will receive quarterly distributions equal to the quarterly distribution per OP Unit plus $0.18 . Beginning on the fifth anniversary of issuance, each Series C Unit holder will receive a fixed quarterly distribution equal to the aggregate quarterly distribution payable in respect of such Series C Unit during the four quarters immediately preceding the fifth anniversary of issuance, divided by four. These distributions are cumulative. The Series C Units became redeemable at the option of the holder one year from the date of issuance, which redemption obligation may be satisfied at the Company’s option in cash or shares of its common stock. The Series C Units are convertible into OP Units at the option of the holder 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 loan receivable, which was collateralized by the Series C Units, bears interest at 5.0% per annum and matures on December 15, 2024 . The Series C Units are shown on the balance sheet net of the loan balance because the borrower under the loan receivable is also the holder of the Series C Units. On December 1, 2018, certain holders of the Series C Units converted their Series C Units into OP Units, with a total of 407,996 Series C Units being converted into a total of 373,113 OP Units. As part of this conversion, the holders of the Series C Units agreed to pledge the OP Units received in the conversion as collateral on the loan receivable to replace the Series C Units that were converted. As of March 31, 2019 and December 31, 2018, the total outstanding balance of the loan receivable was $19,735 , of which $8,644 is shown as a reduction of the noncontrolling interests related to the Series C Units and $11,091 is shown as a reduction of the noncontrolling interests related to the OP Units on the Company's consolidated balance sheets. On April 25, 2019, subsequent to quarter-end, the remaining 296,020 Series C Units were converted into 270,710 OP Units. Series D Redeemable Preferred Units The Partnership Agreement provides for the designation and issuance of the Series D Units. The Series D Units rank junior to the Series A Units, on parity with the Series B Units and Series C Units, and senior to all other partnership interests of the Operating Partnership with respect to distributions and liquidation. The Series D Units have been issued at various times from 2014 to 2017. In addition, during the three months ended March 31, 2019 , the Operating Partnership issued 937,924 Series D Units valued at $23,447 in conjunction with joint venture acquisitions. The Series D Units have a liquidation value of $25.00 per unit, for a fixed liquidation value of $115,511 , which represents 4,620,445 Series D Units. Holders of the Series D Units receive distributions at an annual rate between 3.0% and 5.0% . These distributions are cumulative. The Series D Units become redeemable at the option of the holder on the first anniversary of the date of issuance, which redemption obligation may be satisfied at the Company’s option in cash or shares of its common stock. In addition, certain of the Series D Units are exchangeable for OP Units at the option of the holder until the tenth anniversary of the date of issuance, with the number of OP Units to be issued equal to $25.00 per Series D Unit, divided by the value of a share of common stock as of the exchange date. NONCONTROLLING INTEREST IN OPERATING PARTNERSHIP AND OTHER NONCONTROLLING INTERESTS Noncontrolling Interest in Operating Partnership The Company’s interest in its stores is held through the Operating Partnership. Between its general partner and limited partner interests, the Company held a 90.5% ownership interest in the Operating Partnership as of March 31, 2019 . The remaining ownership interests in the Operating Partnership (including Preferred OP Units) of 9.5% are held by certain former owners of assets acquired by the Operating Partnership. The noncontrolling interest in the Operating Partnership represents OP Units that are not owned by the Company. OP Units are redeemable at the option of the holder, which redemption may be satisfied at the Company's option in cash, based upon the fair market value of an equivalent number of shares of the Company’s common stock (based on the ten -day average trading price) at the time of the redemption, or shares of the Company's common stock on a one-for-one basis , subject to anti-dilution adjustments provided in the Partnership Agreement. As of March 31, 2019 , the ten -day average closing price of the Company's common stock was $100.76 and there were 5,908,750 OP Units outstanding. Assuming that all of the OP Unit holders exercised their right to redeem all of their OP Units on March 31, 2019 and the Company elected to pay the OP Unit holders cash, the Company would have paid $595,366 in cash consideration to redeem the units. OP Unit activity is summarized as follows for the periods presented: For the Three Months Ended March 31, 2019 2018 OP Units redeemed for common stock 85,501 — OP Units redeemed for cash — 30,000 Cash paid for OP Units redeemed $ — $ 2,558 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. Other Noncontrolling Interests Other noncontrolling interests represent the ownership interests of third parties in two consolidated joint ventures as of March 31, 2019 . One joint venture owns two operating stores in Texas, an operating store and a development store in Colorado, and the other joint venture owns one operating store in Pennsylvania and one development property in New Jersey. The voting interests of the third-party owners are between 5.0% and 20.0% .

Leases

Leases	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Leases	LEASES The Company adopted ASC 842, "Leases," effective January 1, 2019 on a modified retrospective basis as allowed under the standard and prior periods have not been restated. The Company elected the package of transition practical expedients, and has therefore (1) not reassessed whether any expired or existing contracts are or contain leases, (2) not reassessed the lease classification for any expired or existing leases, and (3) not reassessed initial direct costs for any expired or existing leases. Lessee Accounting The Company recognized lease liabilities of $104,863 and right-of-use assets related to operating leases totaling $95,506 as of the adoption date. These are presented as “Operating lease liabilities” and “Real estate assets-operating lease right-of-use assets” on the Company’s consolidated balance sheets. The Company is lessee under several types of lease agreements. Generally, these leases fall into the following categories: • Leases of real estate at 22 stores classified as wholly-owned. These leases generally have original lease terms between 10 - 67 years. Under these leases, the Company typically has the option to extend the lease term for additional terms of 5 - 35 years. • Leases of its corporate offices and call center. These leases have original lease terms between 5.3 and 12.1 years, with no extension options. • Leases of 12 regional offices. These leases have original lease terms between three and five years. The Company has the option on five of these leases to extend the lease term for three additional years. • Leases of small district offices. These leases generally have terms of 12 months or less. The Company has made an accounting election to account for these under the short-term lease exception outlined under ASC 842. Therefore, no lease assets or liabilities are recorded related to these leases, and the Company will recognize lease payments as expense on a straight-line basis over the related lease terms. The Company has included lease extension options in the lease term for calculations of its right-of-use assets and liabilities related to the real estate asset leases at its stores when it is reasonably certain that the Company plans to extend these leases when the options arise. Several of the leases of real estate at the Company’s stores include escalation clauses based on an index or rate, such as the Consumer Price Index (CPI). The Company included these lease payments in its calculations of right-of-use assets and liabilities based on the prevailing index or rate as of the adoption date. The Company will recognize changes to these variable lease payments in earnings in the period of the change. One of the real estate leases includes variable lease payments that are based upon a percentage of gross revenues. Certain other leases include additional variable payments relating to a percentage of sales in excess of a specified amount, common area maintenance, property taxes, etc. These payments are variable lease payments that do not depend on an index or rate and are excluded from the measurement of the lease liabilities and right-of-use-assets for these leases. The Company will recognize costs from these variable lease payments in the period in which the obligation for those payments is incurred. The Company has signed a lease agreement for a store in New Jersey. The store is currently under construction by the lessor, and the Company will take possession of the leased asset upon completion of construction, which is estimated to be completed before the end of 2019. The lease term is 75 years from the lease commencement date, with three 10 -year extension options. The Company has also signed a lease agreement for a store in California. The store is under construction by the lessor, and the Company will take possession of the leased asset upon completion of construction, which is estimated to be completed in mid-2020. The lease term is 15 years from the lease commencement date, with three 10 -year extension options and one 5 -year extension option. The Company has not recorded right-of-use assets or lease liabilities related to these leases as of March 31, 2019 as the lease term has not yet commenced for either lease. The lease commencement date will occur when the Company takes possession of the leased asset, and the Company will recognize a lease liability and right-of-use asset relating to the leases at that time. As the Company’s leases do not provide an implicit rate, the Company uses its incremental borrowing rate based on the information available surrounding the Company’s unsecured borrowing rates and implied secured spread at the lease commencement date in determining the present value of lease payments. These discount rates vary depending on the term of the specific leases. Following is information on our total lease costs as of the period(s) indicated: March 31, 2019 Lease cost Finance lease cost: Amortization of finance lease right-of-use assets $ 42 Interest expense related to finance lease liabilities 70 Operating lease cost 2,079 Variable lease cost 912 Short-term lease cost 55 Total lease cost $ 3,158 Cash paid for amounts included in the measurement of lease liabilities Operating cash outflows for finance lease payments $ 57 Operating cash outflows for operating lease payments 3,267 Total cash paid for lease liability measurement $ 3,324 Right-of-use assets obtained in exchange for new operating lease liabilities $ 95,506 Right-of-use assets obtained in exchange for new finance lease liabilities $ 8,050 Weighted average remaining lease term - operating leases (years) 23.7 Weighted average remaining lease term - finance leases (years) 72.5 Weighted average discount rate - operating leases 4.05 % Weighted average discount rate - finance leases 4.25 % Following is information about the Company’s undiscounted cash flows on an annual basis for operating and finance leases, including a reconciliation of the undiscounted cash flows to the finance lease and operating lease liabilities recognized in the Company’s consolidated balance sheets: Operating Finance Total Year 1 $ 8,281 $ 232 $ 8,513 Year 2 8,353 232 8,585 Year 3 8,264 241 8,505 Year 4 7,898 255 8,153 Year 5 7,828 255 8,083 Thereafter 130,052 35,062 165,114 Total $ 170,676 $ 36,277 $ 206,953 Present value adjustments (67,098 ) (31,484 ) (98,582 ) Lease liabilities $ 103,578 $ 4,793 $ 108,371 Lessor Accounting The Company's property rental revenue is primarily related to rents received from tenants at its operating stores. The Company's leases with its self-storage tenants are generally on month-to-month terms, include automatic monthly renewals, allow flexibility to increase rental rates over time as market conditions permit, and provide for the collection of contingent fees such as late fees. These leases do not include any terms or conditions that allow the tenants to purchase the leased space. All self-storage leases for which the Company acts as lessor have been classified as operating leases. The real estate assets related to the Company's stores are included in Real estate assets, net on the Company's condensed consolidated balance sheets and are presented at historical cost less accumulated depreciation and impairment, if any. Rental income related to these operating leases is included in Property rental revenue on the Company's condensed consolidated statements of operations, and is recognized each month during the month-to-month terms at the rental rate in place during each month.
Leases	LEASES The Company adopted ASC 842, "Leases," effective January 1, 2019 on a modified retrospective basis as allowed under the standard and prior periods have not been restated. The Company elected the package of transition practical expedients, and has therefore (1) not reassessed whether any expired or existing contracts are or contain leases, (2) not reassessed the lease classification for any expired or existing leases, and (3) not reassessed initial direct costs for any expired or existing leases. Lessee Accounting The Company recognized lease liabilities of $104,863 and right-of-use assets related to operating leases totaling $95,506 as of the adoption date. These are presented as “Operating lease liabilities” and “Real estate assets-operating lease right-of-use assets” on the Company’s consolidated balance sheets. The Company is lessee under several types of lease agreements. Generally, these leases fall into the following categories: • Leases of real estate at 22 stores classified as wholly-owned. These leases generally have original lease terms between 10 - 67 years. Under these leases, the Company typically has the option to extend the lease term for additional terms of 5 - 35 years. • Leases of its corporate offices and call center. These leases have original lease terms between 5.3 and 12.1 years, with no extension options. • Leases of 12 regional offices. These leases have original lease terms between three and five years. The Company has the option on five of these leases to extend the lease term for three additional years. • Leases of small district offices. These leases generally have terms of 12 months or less. The Company has made an accounting election to account for these under the short-term lease exception outlined under ASC 842. Therefore, no lease assets or liabilities are recorded related to these leases, and the Company will recognize lease payments as expense on a straight-line basis over the related lease terms. The Company has included lease extension options in the lease term for calculations of its right-of-use assets and liabilities related to the real estate asset leases at its stores when it is reasonably certain that the Company plans to extend these leases when the options arise. Several of the leases of real estate at the Company’s stores include escalation clauses based on an index or rate, such as the Consumer Price Index (CPI). The Company included these lease payments in its calculations of right-of-use assets and liabilities based on the prevailing index or rate as of the adoption date. The Company will recognize changes to these variable lease payments in earnings in the period of the change. One of the real estate leases includes variable lease payments that are based upon a percentage of gross revenues. Certain other leases include additional variable payments relating to a percentage of sales in excess of a specified amount, common area maintenance, property taxes, etc. These payments are variable lease payments that do not depend on an index or rate and are excluded from the measurement of the lease liabilities and right-of-use-assets for these leases. The Company will recognize costs from these variable lease payments in the period in which the obligation for those payments is incurred. The Company has signed a lease agreement for a store in New Jersey. The store is currently under construction by the lessor, and the Company will take possession of the leased asset upon completion of construction, which is estimated to be completed before the end of 2019. The lease term is 75 years from the lease commencement date, with three 10 -year extension options. The Company has also signed a lease agreement for a store in California. The store is under construction by the lessor, and the Company will take possession of the leased asset upon completion of construction, which is estimated to be completed in mid-2020. The lease term is 15 years from the lease commencement date, with three 10 -year extension options and one 5 -year extension option. The Company has not recorded right-of-use assets or lease liabilities related to these leases as of March 31, 2019 as the lease term has not yet commenced for either lease. The lease commencement date will occur when the Company takes possession of the leased asset, and the Company will recognize a lease liability and right-of-use asset relating to the leases at that time. As the Company’s leases do not provide an implicit rate, the Company uses its incremental borrowing rate based on the information available surrounding the Company’s unsecured borrowing rates and implied secured spread at the lease commencement date in determining the present value of lease payments. These discount rates vary depending on the term of the specific leases. Following is information on our total lease costs as of the period(s) indicated: March 31, 2019 Lease cost Finance lease cost: Amortization of finance lease right-of-use assets $ 42 Interest expense related to finance lease liabilities 70 Operating lease cost 2,079 Variable lease cost 912 Short-term lease cost 55 Total lease cost $ 3,158 Cash paid for amounts included in the measurement of lease liabilities Operating cash outflows for finance lease payments $ 57 Operating cash outflows for operating lease payments 3,267 Total cash paid for lease liability measurement $ 3,324 Right-of-use assets obtained in exchange for new operating lease liabilities $ 95,506 Right-of-use assets obtained in exchange for new finance lease liabilities $ 8,050 Weighted average remaining lease term - operating leases (years) 23.7 Weighted average remaining lease term - finance leases (years) 72.5 Weighted average discount rate - operating leases 4.05 % Weighted average discount rate - finance leases 4.25 % Following is information about the Company’s undiscounted cash flows on an annual basis for operating and finance leases, including a reconciliation of the undiscounted cash flows to the finance lease and operating lease liabilities recognized in the Company’s consolidated balance sheets: Operating Finance Total Year 1 $ 8,281 $ 232 $ 8,513 Year 2 8,353 232 8,585 Year 3 8,264 241 8,505 Year 4 7,898 255 8,153 Year 5 7,828 255 8,083 Thereafter 130,052 35,062 165,114 Total $ 170,676 $ 36,277 $ 206,953 Present value adjustments (67,098 ) (31,484 ) (98,582 ) Lease liabilities $ 103,578 $ 4,793 $ 108,371 Lessor Accounting The Company's property rental revenue is primarily related to rents received from tenants at its operating stores. The Company's leases with its self-storage tenants are generally on month-to-month terms, include automatic monthly renewals, allow flexibility to increase rental rates over time as market conditions permit, and provide for the collection of contingent fees such as late fees. These leases do not include any terms or conditions that allow the tenants to purchase the leased space. All self-storage leases for which the Company acts as lessor have been classified as operating leases. The real estate assets related to the Company's stores are included in Real estate assets, net on the Company's condensed consolidated balance sheets and are presented at historical cost less accumulated depreciation and impairment, if any. Rental income related to these operating leases is included in Property rental revenue on the Company's condensed consolidated statements of operations, and is recognized each month during the month-to-month terms at the rental rate in place during each month.
Leases	LEASES The Company adopted ASC 842, "Leases," effective January 1, 2019 on a modified retrospective basis as allowed under the standard and prior periods have not been restated. The Company elected the package of transition practical expedients, and has therefore (1) not reassessed whether any expired or existing contracts are or contain leases, (2) not reassessed the lease classification for any expired or existing leases, and (3) not reassessed initial direct costs for any expired or existing leases. Lessee Accounting The Company recognized lease liabilities of $104,863 and right-of-use assets related to operating leases totaling $95,506 as of the adoption date. These are presented as “Operating lease liabilities” and “Real estate assets-operating lease right-of-use assets” on the Company’s consolidated balance sheets. The Company is lessee under several types of lease agreements. Generally, these leases fall into the following categories: • Leases of real estate at 22 stores classified as wholly-owned. These leases generally have original lease terms between 10 - 67 years. Under these leases, the Company typically has the option to extend the lease term for additional terms of 5 - 35 years. • Leases of its corporate offices and call center. These leases have original lease terms between 5.3 and 12.1 years, with no extension options. • Leases of 12 regional offices. These leases have original lease terms between three and five years. The Company has the option on five of these leases to extend the lease term for three additional years. • Leases of small district offices. These leases generally have terms of 12 months or less. The Company has made an accounting election to account for these under the short-term lease exception outlined under ASC 842. Therefore, no lease assets or liabilities are recorded related to these leases, and the Company will recognize lease payments as expense on a straight-line basis over the related lease terms. The Company has included lease extension options in the lease term for calculations of its right-of-use assets and liabilities related to the real estate asset leases at its stores when it is reasonably certain that the Company plans to extend these leases when the options arise. Several of the leases of real estate at the Company’s stores include escalation clauses based on an index or rate, such as the Consumer Price Index (CPI). The Company included these lease payments in its calculations of right-of-use assets and liabilities based on the prevailing index or rate as of the adoption date. The Company will recognize changes to these variable lease payments in earnings in the period of the change. One of the real estate leases includes variable lease payments that are based upon a percentage of gross revenues. Certain other leases include additional variable payments relating to a percentage of sales in excess of a specified amount, common area maintenance, property taxes, etc. These payments are variable lease payments that do not depend on an index or rate and are excluded from the measurement of the lease liabilities and right-of-use-assets for these leases. The Company will recognize costs from these variable lease payments in the period in which the obligation for those payments is incurred. The Company has signed a lease agreement for a store in New Jersey. The store is currently under construction by the lessor, and the Company will take possession of the leased asset upon completion of construction, which is estimated to be completed before the end of 2019. The lease term is 75 years from the lease commencement date, with three 10 -year extension options. The Company has also signed a lease agreement for a store in California. The store is under construction by the lessor, and the Company will take possession of the leased asset upon completion of construction, which is estimated to be completed in mid-2020. The lease term is 15 years from the lease commencement date, with three 10 -year extension options and one 5 -year extension option. The Company has not recorded right-of-use assets or lease liabilities related to these leases as of March 31, 2019 as the lease term has not yet commenced for either lease. The lease commencement date will occur when the Company takes possession of the leased asset, and the Company will recognize a lease liability and right-of-use asset relating to the leases at that time. As the Company’s leases do not provide an implicit rate, the Company uses its incremental borrowing rate based on the information available surrounding the Company’s unsecured borrowing rates and implied secured spread at the lease commencement date in determining the present value of lease payments. These discount rates vary depending on the term of the specific leases. Following is information on our total lease costs as of the period(s) indicated: March 31, 2019 Lease cost Finance lease cost: Amortization of finance lease right-of-use assets $ 42 Interest expense related to finance lease liabilities 70 Operating lease cost 2,079 Variable lease cost 912 Short-term lease cost 55 Total lease cost $ 3,158 Cash paid for amounts included in the measurement of lease liabilities Operating cash outflows for finance lease payments $ 57 Operating cash outflows for operating lease payments 3,267 Total cash paid for lease liability measurement $ 3,324 Right-of-use assets obtained in exchange for new operating lease liabilities $ 95,506 Right-of-use assets obtained in exchange for new finance lease liabilities $ 8,050 Weighted average remaining lease term - operating leases (years) 23.7 Weighted average remaining lease term - finance leases (years) 72.5 Weighted average discount rate - operating leases 4.05 % Weighted average discount rate - finance leases 4.25 % Following is information about the Company’s undiscounted cash flows on an annual basis for operating and finance leases, including a reconciliation of the undiscounted cash flows to the finance lease and operating lease liabilities recognized in the Company’s consolidated balance sheets: Operating Finance Total Year 1 $ 8,281 $ 232 $ 8,513 Year 2 8,353 232 8,585 Year 3 8,264 241 8,505 Year 4 7,898 255 8,153 Year 5 7,828 255 8,083 Thereafter 130,052 35,062 165,114 Total $ 170,676 $ 36,277 $ 206,953 Present value adjustments (67,098 ) (31,484 ) (98,582 ) Lease liabilities $ 103,578 $ 4,793 $ 108,371 Lessor Accounting The Company's property rental revenue is primarily related to rents received from tenants at its operating stores. The Company's leases with its self-storage tenants are generally on month-to-month terms, include automatic monthly renewals, allow flexibility to increase rental rates over time as market conditions permit, and provide for the collection of contingent fees such as late fees. These leases do not include any terms or conditions that allow the tenants to purchase the leased space. All self-storage leases for which the Company acts as lessor have been classified as operating leases. The real estate assets related to the Company's stores are included in Real estate assets, net on the Company's condensed consolidated balance sheets and are presented at historical cost less accumulated depreciation and impairment, if any. Rental income related to these operating leases is included in Property rental revenue on the Company's condensed consolidated statements of operations, and is recognized each month during the month-to-month terms at the rental rate in place during each month.

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Segment Information	SEGMENT INFORMATION The Company’s segment disclosures present the measure used by the chief operating decision makers ("CODMs") for purposes of assessing each segment’s performance. The Company’s CODMs are comprised of several members of its executive management team who use net operating income ("NOI") to assess the performance of the business for the Company’s reportable operating segments. NOI for the Company's self-storage operations represents total property revenue less direct property operating expenses. NOI for the Company's tenant reinsurance segment represents tenant reinsurance revenues less tenant reinsurance expense. The Company has two reportable segments: (1) self-storage operations and (2) tenant reinsurance. The self-storage operations activities include rental operations of wholly-owned stores. The Company's consolidated revenues equal total segment revenues plus property management fees and other income. Tenant reinsurance activities include the reinsurance of risks relating to the loss of goods stored by tenants in the stores operated by the Company. Excluded from segment revenues and net operating income is property management fees and other income. For all periods presented, substantially all of the Company's real estate assets, intangible assets, other assets, and accrued and other liabilities are associated with the self-storage operations segment. The prior periods have been restated to conform to the current presentation. Financial information for the Company’s business segments is set forth below: For the Three Months Ended March 31, 2019 2018 Revenues: Self-Storage Operations $ 271,003 $ 247,886 Tenant Reinsurance 29,797 27,034 Total segment revenues $ 300,800 $ 274,920 Operating expenses: Self-Storage Operations $ 78,765 $ 72,753 Tenant Reinsurance 6,967 5,607 Total segment operating expenses $ 85,732 $ 78,360 Net operating income: Self-Storage Operations $ 192,238 $ 175,133 Tenant Reinsurance 22,830 21,427 Total segment net operating income: $ 215,068 $ 196,560 Other components of net income (loss): Property management fees and other income $ 10,746 $ 10,565 General and administrative expense (22,678 ) (21,464 ) Depreciation and amortization expense (54,659 ) (51,749 ) Interest expense (47,360 ) (40,966 ) Non-cash interest expense related to the amortization of discount on equity component of exchangeable senior notes (1,162 ) (1,209 ) Interest income 1,388 1,438 Equity in earnings of unconsolidated real estate ventures 2,630 3,597 Income tax expense (1,813 ) (1,342 ) Net income $ 102,160 $ 95,430

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES As of March 31, 2019 , the Company was involved in various legal proceedings and was subject to various claims and complaints arising in the ordinary course of business. Because litigation is inherently unpredictable, the outcome of these matters cannot presently be determined with any degree of certainty. In accordance with applicable accounting guidance, management establishes an accrued liability for litigation when those matters present loss contingencies that are both probable and reasonably estimable. In such cases, there may be an exposure to loss in excess of any amounts accrued. The estimated loss, if any, is based upon currently available information and is subject to significant judgment, a variety of assumptions, and known and unknown uncertainties. The Company could in the future incur judgments or enter into settlements of claims that could have a material adverse effect on its results of operations in any particular period, notwithstanding the fact that the Company is currently vigorously defending any legal proceedings against it. As of March 31, 2019 , the Company was under agreement to acquire six stores at a total purchase price of $67,028 . Of these stores, three are scheduled to close in 2019 at a purchase price of $31,600 , and three are scheduled to close in 2020 at a purchase price of $35,428 . Additionally, the Company is under agreement to acquire six stores with joint venture partners, for a total investment of $25,346 . Five of these stores are scheduled to close in 2019 and the remaining store is expected to close in 2020. Although there can be no assurance, the Company is not aware of any material environmental liability, for which it believes it will be ultimately responsible, that could have a material adverse effect on its financial condition or results of operations. However, changes in applicable environmental laws and regulations, the uses and conditions of properties in the vicinity of the Company’s stores, the activities of its tenants and other environmental conditions of which the Company is unaware with respect to its stores could result in future material environmental liabilities.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	SUBSEQUENT EVENTS Subsequent to March 31, 2019 , the Company sold one store located in New York for a total purchase price of $11,781 . The Company recognized a gain of approximately $1,200 related to this sale. On April 25, 2019, all of the Company's 296,020 Series C Units were converted into 270,710 OP Units.

Basis of Presentation (Policies

Basis of Presentation (Policies)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Basis of Presentation	The accompanying unaudited condensed consolidated financial statements of the Company are presented on the accrual basis of accounting in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information, and in accordance with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they may not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, all adjustments (including normal recurring accruals) considered necessary for a fair presentation have been included. Operating results for the three months ended March 31, 2019 are not necessarily indicative of results that may be expected for the year ending December 31, 2019 . The condensed consolidated balance sheet as of December 31, 2018 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, 2018 , as filed with the Securities and Exchange Commission.
Recently Issued Accounting Standards	Recently Issued Accounting Standards In February 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2016-02, “Leases (Topic 842),” which modifies the accounting for leases, intending to increase transparency and comparability of organizations by requiring balance sheet presentation of leased assets and increased financial statement disclosure of leasing arrangements. ASU 2016-02 requires entities to recognize a liability for their lease obligations and a corresponding asset representing the right to use the underlying asset over the lease term. Lease obligations are measured at their present value and accounted for using the effective interest method. The accounting for the leased asset differs slightly depending on whether the agreement is deemed to be a financing or operating lease. For financing leases, the leased asset is depreciated on a straight-line basis and is recorded separately from the interest expense in the statements of operations, resulting in higher expense in the earlier part of the lease term. For operating leases, the depreciation and interest expense components are combined, recognized evenly over the term of the lease, and presented as a reduction to operating income. ASU 2016-02 requires that assets and liabilities be presented or disclosed separately, and requires additional disclosure of certain qualitative and quantitative information related to these lease agreements. ASU 2016-02 is effective for annual and interim periods beginning after December 15, 2018. The Company adopted the standard using the modified retrospective approach as of January 1, 2019. The Company elected the package of practical expedients upon adoption, which allows for the application of the standard solely to the transition period in 2019 but does not require application to prior fiscal comparative periods presented. The Company also elected the practical expedient provided in a subsequent amendment to the standard that removed the requirement to separate lease and nonlease components. The Company did not record a significant cumulative catch-up adjustment to retained earnings upon adoption of ASU 2016-02. The primary impact was related to the Company's 21 operating ground leases and two corporate facility leases under which it serves as lessee. The Company recognized lease liabilities of $104,863 and right-of-use assets related to operating leases totaling $95,506 as of the adoption date. Refer to Note 13 for further discussion of the Company's leases. In August 2018, the FASB issued ASU 2018-15, "Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40): Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That is a Service Contract." ASU 2018-15 amends the accounting for implementation costs incurred in a hosting arrangement that is a service contract, and aligns them with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. ASU 2018-15 also requires that entities amortize the capitalized implementation costs over the term of the hosting arrangement. ASU 2018-15 is effective for annual periods beginning after December 15, 2020, with early adoption permitted, including early adoption in any interim period. The Company adopted this standard on a prospective basis as of October 1, 2018. The adoption of this standard did not have a material impact on the Company's financial statements. In June 2016, the FASB issued ASU 2016-13, "Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments." ASU 2016-13 changes how entities measure credit losses for most financial assets. This standard requires an entity to estimate its lifetime "expected credit loss" and record an allowance that, when deducted from the amortized cost basis of the financial asset, presents the net amount expected to be collected on the financial asset. The Company is evaluating the impact this new standard will have on its consolidated financial statements. In November 2018, the FASB issued ASU 2018-19, "Codification Improvements to Topic 326, Financial Instruments - Credit Losses," which clarified that receivables arising from operating leases are within the scope of the leasing standard (ASU 2016-02). This new standard will be effective for the Company on January 1, 2020. The Company is evaluating the impact this new standard will have on its consolidated financial statements.
Fair Value Disclosures	Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis Long-lived assets held for use are evaluated for impairment when events or circumstances indicate there may be impairment. The Company reviews each store at least annually to determine if any such events or circumstances have occurred or exist. The Company focuses on stores where occupancy and/or rental income have decreased by a significant amount. For these stores, the Company determines whether the decrease is temporary or permanent, and whether the store will likely recover the lost occupancy and/or revenue in the short term. In addition, the Company reviews stores in the lease-up stage and compares actual operating results to original projections. When the Company determines that an event that may indicate impairment has occurred, the Company compares the carrying value of the related long-lived assets to the undiscounted future net operating cash flows attributable to the assets. An impairment loss is recorded if the net carrying value of the assets exceeds the undiscounted future net operating cash flows attributable to the assets. The impairment loss recognized equals the excess of net carrying value over the related fair value of the assets. When real estate assets are identified by management as held for sale, the Company discontinues depreciating the assets and estimates the fair value of the assets, net of selling costs. If the estimated fair value, net of selling costs, of the assets that have been identified as held for sale is less than the net carrying value of the assets, the Company would recognize an impairment loss on the assets held for sale. The operations of assets held for sale or sold during the period are presented as part of normal operations for all periods presented. As of March 31, 2019 , the Company had one operating store classified as held for sale and one parcel of land classified as held for sale which are included in real estate assets, net. The estimated fair value less selling costs for each of these assets is greater than the carrying value of the assets, and therefore no loss has been recorded. The Company assesses annually whether there are any indicators that the value of the Company’s investments in unconsolidated real estate ventures may be impaired 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 relative fair values, which are estimated using significant unobservable inputs. The value of the tangible assets, consisting of land and buildings, is determined as if vacant. Intangible assets, which represent the value of existing tenant relationships, are recorded at their fair values based on the avoided cost to replace the current leases. The Company measures the value of tenant relationships based on the rent lost due to the amount of time required to replace existing customers, which is based on the Company’s historical experience with turnover in its stores. Any debt assumed as part of an acquisition is recorded at fair value based on current interest rates compared to contractual rates. Acquisition-related transaction costs are capitalized as part of the purchase price. Fair Value of Financial Instruments The carrying values of cash and cash equivalents, restricted cash, receivables, other financial instruments included in other assets, accounts payable and accrued expenses, variable-rate notes payable, lines of credit and other liabilities reflected in the condensed consolidated balance sheets at March 31, 2019 and December 31, 2018 approximate fair value. Restricted cash is comprised of letters of credit and escrowed funds deposited with financial institutions located throughout the United States relating to earnest money deposits on potential acquisitions, real estate taxes, insurance and capital expenditures. The fair values of the Company’s notes receivable from Preferred Operating Partnership unit holders and other fixed rate notes receivable, which are recorded in other assets, net 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. Derivative Financial Instruments Currently, the Company uses interest rate swaps to manage its interest rate risk. The valuation of these instruments is determined using widely accepted valuation techniques, including discounted cash flow analysis on the expected cash flows of each derivative. This analysis reflects the contractual terms of the derivatives, including the period to maturity, and uses observable market-based inputs, including interest rate curves. The fair values of interest rate swaps are determined using the market standard methodology of netting the discounted future fixed cash payments and the discounted expected variable cash receipts. The variable cash receipts are based on an expectation of future interest rates (forward curves) derived from observable market interest rate forward curves. The Company incorporates credit valuation adjustments to appropriately reflect both its own nonperformance risk and the respective counterparty’s nonperformance risk in the fair value measurements. In adjusting the fair value of its derivative contracts for the effect of nonperformance risk, the Company has considered the impact of netting and any applicable credit enhancements, such as collateral postings, thresholds, mutual puts and guarantees. In conjunction with the FASB’s fair value measurement guidance, the Company made an accounting policy election to measure the credit risk of its derivative financial instruments that are subject to master netting agreements on a net basis by counterparty portfolio. Although the Company has determined that the majority of the inputs used to value its derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with its derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default by the Company and its counterparties. However, as of March 31, 2019 , the Company 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 has determined that its derivative valuations in their entirety were classified in Level 2 of the fair value hierarchy.
Earnings Per Common Share	Basic earnings per common share is computed using the two-class method by dividing net income attributable to common stockholders by the weighted average number of common shares outstanding during the period. All outstanding unvested restricted stock awards contain rights to non-forfeitable dividends and participate in undistributed earnings with common stockholders; accordingly, they are considered participating securities that are included in the two-class method. Diluted earnings per common share measures the performance of the Company over the reporting period while giving effect to all potential common shares that were dilutive and outstanding during the period. The denominator includes the weighted average number of basic shares and the number of additional common shares that would have been outstanding if the potential common shares that were dilutive had been issued, and is calculated using either the two-class, treasury stock or as if-converted method, whichever is most dilutive. Potential common shares are securities (such as options, convertible debt, Series A Participating Redeemable Preferred Units (“Series A Units”), Series B Redeemable Preferred Units (“Series B Units”), Series C Convertible Redeemable Preferred Units (“Series C Units”), Series D Redeemable Preferred Units (“Series D Units” and, together with the Series A Units, Series B Units and Series C Units, the “Preferred OP Units”) and common Operating Partnership units (“OP Units”)) that do not have a current right to participate in earnings of the Company but could do so in the future by virtue of their option, redemption or conversion right. In computing the dilutive effect of convertible securities, net income is adjusted to add back any changes in earnings in the period associated with the convertible security. The numerator also is adjusted for the effects of any other non-discretionary changes in income or loss that would result from the assumed conversion of those potential common shares. In computing diluted earnings per common share, only potential common shares that are dilutive (i.e. those that reduce earnings per common share) are included.
Derivatives	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. 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 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.

Fair Value Disclosures (Tables)

Fair Value Disclosures (Tables)	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The table below presents the Company’s assets and liabilities measured at fair value on a recurring basis as of March 31, 2019 , aggregated by the level in the fair value hierarchy within which those measurements fall. Fair Value Measurements at Reporting Date Using Description 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 $ — $ 25,908 $ — Other liabilities - cash flow hedge swap agreements $ — $ 9,307 $ —
Schedule of Fair Value of Financial Instruments	The fair values of the Company’s fixed-rate assets and liabilities were as follows for the periods indicated: March 31, 2019 December 31, 2018 Fair Carrying Fair Carrying Notes receivable from Preferred and Common Operating Partnership unit holders $ 116,957 $ 119,735 $ 115,467 $ 119,735 Fixed rate notes payable and notes payable to trusts $ 3,057,072 $ 3,051,171 $ 2,985,731 $ 3,022,414 Exchangeable senior notes $ 660,894 $ 575,000 $ 620,149 $ 575,000

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	3 Months Ended
	Mar. 31, 2019
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. For the Three Months Ended March 31, 2019 2018 Equivalent Shares (if converted) Equivalent Shares (if converted) Series B Units 436,254 498,183 Series C Units 129,763 352,385 Series D Units 1,083,265 1,094,555 1,649,282 1,945,123
Schedule of Computation of Earnings Per Common Share	The computation of earnings per common share is as follows for the periods presented: For the Three Months Ended March 31, 2019 2018 Net income attributable to common stockholders $ 94,770 $ 88,256 Earnings and dividends allocated to participating securities (167 ) (178 ) Earnings for basic computations 94,603 88,078 Earnings and dividends allocated to participating securities — 178 Income allocated to noncontrolling interest - Preferred Operating Partnership Units and Operating Partnership Units 5,429 4,941 Fixed component of income allocated to noncontrolling interest - Preferred Operating Partnership (Series A Units) (572 ) (572 ) Net income for diluted computations $ 99,460 $ 92,625 Weighted average common shares outstanding: Average number of common shares outstanding - basic 127,037,247 125,772,439 OP Units 5,960,981 5,663,370 Series A Units 875,480 875,480 Shares related to exchangeable senior notes and dilutive stock options 416,008 371,271 Average number of common shares outstanding - diluted 134,289,716 132,682,560 Earnings per common share Basic $ 0.74 $ 0.70 Diluted $ 0.74 $ 0.70

Store Acquisitions and Dispos_2

Store Acquisitions and Dispositions (Tables)	3 Months Ended
	Mar. 31, 2019
Real Estate [Abstract]
Schedule of Operating Properties Acquired	The following table shows the Company’s acquisitions of stores for the three months ended March 31, 2019 and 2018 . The table excludes purchases of raw land and improvements made to existing assets. All acquisitions are considered asset acquisitions under ASU 2017-01, " Business Combinations (Topic 805): Clarifying the Definition of a Business ." Consideration Paid Total Quarter Number of Stores Total Cash Paid Loan Assumed Investments in Real Estate Ventures Net Liabilities/ (Assets) Assumed Real estate assets Q1 2019 14 (1) $ 223,740 $ 202,890 $ 17,157 $ 2,780 $ 913 $ 223,740 Q1 2018 5 (2) $ 70,787 $ 70,171 $ — $ 489 $ 127 $ 70,787 (1) Store acquisitions during the three months ended March 31, 2019 include the purchase of 12 stores previously held in joint ventures where the Company held a noncontrolling interest. The Company purchased its partners' remaining equity interests in the joint ventures, and the properties owned by the joint ventures became wholly owned by the Company. No gain or loss was recognized as a result of this acquisition. (2) Store acquisitions during the three months ended March 31, 2018 include the acquisition of one store that had been owned by a joint venture in which the Company held a noncontrolling interest. No gain or loss was recognized as a result of this acquisition.

Investments in Unconsolidated_2

Investments in Unconsolidated Real Estate Ventures - (Tables)	3 Months Ended
	Mar. 31, 2019
Equity Method Investments and Joint Ventures [Abstract]
Schedule of investments in unconsolidated real estate ventures	Net investments in unconsolidated real estate ventures and cash distributions in unconsolidated real estate ventures consist of the following: Number of Stores Equity Ownership % Excess Profit % (1) March 31, December 31, 2019 2018 PRISA Self Storage LLC 85 4% 4% $ 9,292 $ 9,334 Storage Portfolio II JV LLC 36 10% 30% (4,539 ) (4,233 ) Storage Portfolio I LLC 24 34% 49% (38,186 ) (38,129 ) VRS Self Storage, LLC 16 45% 54% 18,002 18,281 Extra Space Northern Properties Six LLC 10 10% 35% (1,793 ) (1,700 ) WICNN JV LLC 9 10% 25% 32,859 26,885 Alan Jathoo JV LLC 9 10% 10% 8,132 8,180 ESS Bristol Investments LLC 8 10% 28% 3,025 2,331 GFN JV, LLC 5 10% 25% 12,429 10,586 Extra Space West Two LLC — 5% 40% — (2 ) 3,818 Extra Space West One LLC — 5% 40% — (2 ) (1,038 ) Other minority owned stores 22 10-50% 19-50% 77,238 45,814 Net Investments in and Cash distributions in unconsolidated real estate ventures 224 $ 116,459 $ 80,129 (1) Includes pro-rata equity ownership share and promoted interest. (2) In January 2019, the Company purchased its joint venture partners' 95% interests in the Extra Space West One LLC and Extra Space West Two LLC joint ventures, which owned a total of 12 stores. The Company paid $172,505 of cash to acquire the equity interests, and subsequent to this acquisition, the Company owned 100% of the joint ventures and the related stores.

Derivatives (Tables)

Derivatives (Tables)	3 Months Ended
	Mar. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of balance sheet classification and fair value of entity's derivative financial instruments	The table below presents the fair value of the Company’s derivative financial instruments as well as their classification on the condensed consolidated balance sheets: Asset / Liability Derivatives March 31, 2019 December 31, 2018 Derivatives designated as hedging instruments: Fair Value Other assets $ 25,908 $ 42,324 Other liabilities $ 9,307 $ 2,131
Schedule of information relating to gain (loss) recognized on swap agreements	The table below presents 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: Gain (loss) recognized in OCI For the Three Months Ended March 31, Location of amounts reclassified from OCI into income Gain reclassified from OCI For the Three Months Ended March 31, Type 2019 2018 2019 2018 Swap Agreements $ (19,576 ) $ 23,317 Interest expense $ 4,462 $ 240

Exchangeable Senior Notes (Tabl

Exchangeable Senior Notes (Tables)	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Schedule of information about total carrying amounts of equity components, principal amounts of liability components, unamortized discounts and net carrying amounts for notes	Information about the Company’s 2015 Notes, including the total carrying amount of the equity component, the principal amount of the liability component, the unamortized discount and the net carrying amount was as follows for the periods indicated: March 31, 2019 December 31, 2018 Carrying amount of equity component $ 22,597 $ 22,597 Principal amount of liability component $ 575,000 $ 575,000 Unamortized discount - equity component (7,255 ) (8,417 ) Unamortized debt issuance costs (3,609 ) (4,209 ) Net carrying amount of liability components $ 564,136 $ 562,374
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 rate and the amortization of the discount on the liability component of the 2015 Notes were as follows for the periods indicated: For the Three Months Ended March 31, 2019 2018 Contractual interest $ 4,492 $ 4,561 Amortization of discount 1,162 1,209 Total interest expense recognized $ 5,654 $ 5,770

Noncontrolling Interest in Op_2

Noncontrolling Interest in Operating Partnership (Tables)	3 Months Ended
	Mar. 31, 2019
Noncontrolling Interest [Abstract]
Redeemable Noncontrolling Interest	OP Unit activity is summarized as follows for the periods presented: For the Three Months Ended March 31, 2019 2018 OP Units redeemed for common stock 85,501 — OP Units redeemed for cash — 30,000 Cash paid for OP Units redeemed $ — $ 2,558

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Lease costs	Following is information on our total lease costs as of the period(s) indicated: March 31, 2019 Lease cost Finance lease cost: Amortization of finance lease right-of-use assets $ 42 Interest expense related to finance lease liabilities 70 Operating lease cost 2,079 Variable lease cost 912 Short-term lease cost 55 Total lease cost $ 3,158 Cash paid for amounts included in the measurement of lease liabilities Operating cash outflows for finance lease payments $ 57 Operating cash outflows for operating lease payments 3,267 Total cash paid for lease liability measurement $ 3,324 Right-of-use assets obtained in exchange for new operating lease liabilities $ 95,506 Right-of-use assets obtained in exchange for new finance lease liabilities $ 8,050 Weighted average remaining lease term - operating leases (years) 23.7 Weighted average remaining lease term - finance leases (years) 72.5 Weighted average discount rate - operating leases 4.05 % Weighted average discount rate - finance leases 4.25 %
Undiscounted cash flows on an annual basis, operating leases	Following is information about the Company’s undiscounted cash flows on an annual basis for operating and finance leases, including a reconciliation of the undiscounted cash flows to the finance lease and operating lease liabilities recognized in the Company’s consolidated balance sheets: Operating Finance Total Year 1 $ 8,281 $ 232 $ 8,513 Year 2 8,353 232 8,585 Year 3 8,264 241 8,505 Year 4 7,898 255 8,153 Year 5 7,828 255 8,083 Thereafter 130,052 35,062 165,114 Total $ 170,676 $ 36,277 $ 206,953 Present value adjustments (67,098 ) (31,484 ) (98,582 ) Lease liabilities $ 103,578 $ 4,793 $ 108,371
Undiscounted cash flows on an annual basis, finance leases	Following is information about the Company’s undiscounted cash flows on an annual basis for operating and finance leases, including a reconciliation of the undiscounted cash flows to the finance lease and operating lease liabilities recognized in the Company’s consolidated balance sheets: Operating Finance Total Year 1 $ 8,281 $ 232 $ 8,513 Year 2 8,353 232 8,585 Year 3 8,264 241 8,505 Year 4 7,898 255 8,153 Year 5 7,828 255 8,083 Thereafter 130,052 35,062 165,114 Total $ 170,676 $ 36,277 $ 206,953 Present value adjustments (67,098 ) (31,484 ) (98,582 ) Lease liabilities $ 103,578 $ 4,793 $ 108,371

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Schedule of Financial Information of Business Segments	Financial information for the Company’s business segments is set forth below: For the Three Months Ended March 31, 2019 2018 Revenues: Self-Storage Operations $ 271,003 $ 247,886 Tenant Reinsurance 29,797 27,034 Total segment revenues $ 300,800 $ 274,920 Operating expenses: Self-Storage Operations $ 78,765 $ 72,753 Tenant Reinsurance 6,967 5,607 Total segment operating expenses $ 85,732 $ 78,360 Net operating income: Self-Storage Operations $ 192,238 $ 175,133 Tenant Reinsurance 22,830 21,427 Total segment net operating income: $ 215,068 $ 196,560 Other components of net income (loss): Property management fees and other income $ 10,746 $ 10,565 General and administrative expense (22,678 ) (21,464 ) Depreciation and amortization expense (54,659 ) (51,749 ) Interest expense (47,360 ) (40,966 ) Non-cash interest expense related to the amortization of discount on equity component of exchangeable senior notes (1,162 ) (1,209 ) Interest income 1,388 1,438 Equity in earnings of unconsolidated real estate ventures 2,630 3,597 Income tax expense (1,813 ) (1,342 ) Net income $ 102,160 $ 95,430

Organization - Additional Infor

Organization - Additional Information (Detail)	Mar. 31, 2019storestate
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of operating storage facilities in which the entity has equity interests (in stores)	1,119
Number of stores owned by franchisees and third parties	577
Number of operating stores owned and/or managed	1,696
Number of states in which operating storage facilities are located | state	40

Basis of Presentation - Narrati

Basis of Presentation - Narrative (Details) $ in Thousands	Mar. 31, 2019USD ($)	Jan. 01, 2019USD ($)	Dec. 31, 2018USD ($)lease
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease liabilities	$ 103,578		$ 0
Operating lease right-of-use assets	$ 94,198		$ 0
Operating ground leases
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of leases | lease			21
Corporate facility leases
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of leases | lease			2
ASU 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease liabilities		$ 104,863
Operating lease right-of-use assets		$ 95,506

Fair Value Disclosures - Schedu

Fair Value Disclosures - Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) - Recurring Basis $ in Thousands	Mar. 31, 2019USD ($)
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets - cash flow hedge swap agreements	$ 0
Other liabilities - cash flow hedge swap agreements	0
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets - cash flow hedge swap agreements	25,908
Other liabilities - cash flow hedge swap agreements	9,307
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets - cash flow hedge swap agreements	0
Other liabilities - cash flow hedge swap agreements	$ 0

Fair Value Disclosures - Additi

Fair Value Disclosures - Additional Information (Detail)	Mar. 31, 2019storeland_parcel
Fair Value Disclosures [Abstract]
Number of operating stores held for sale | store	1
Number of parcels of land held-for-sale | land_parcel	1

Fair Value Disclosures - Sche_2

Fair Value Disclosures - Schedule of Fair Value of Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Fair Value
Fair Value of Financial Instruments [Line Items]
Notes receivable from Preferred and Common Operating Partnership unit holders	$ 116,957	$ 115,467
Fixed rate notes payable and notes payable to trusts	3,057,072	2,985,731
Exchangeable senior notes	660,894	620,149
Carrying Value
Fair Value of Financial Instruments [Line Items]
Notes receivable from Preferred and Common Operating Partnership unit holders	119,735	119,735
Fixed rate notes payable and notes payable to trusts	3,051,171	3,022,414
Exchangeable senior notes	$ 575,000	$ 575,000

Earnings Per Common Share - Add

Earnings Per Common Share - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Sep. 30, 2015	Jun. 21, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Average share price (in dollars per share)	$ 96.05	$ 84.11
Principal amount of notes outstanding	$ 564,136,000		$ 562,374,000
Exchangeable Senior Notes 2.375% due 2033 (the 2013 Notes)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Principal amount of notes outstanding	$ 0
Debt stated interest rate	2.375%				2.375%
Shares related to the Notes included in the computation for diluted earnings per share (in shares)	0	81,382
Exchangeable Senior Notes 3.125% due 2035 (the 2015 Notes)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Principal amount of notes outstanding	$ 575,000,000
Debt stated interest rate	3.125%			3.125%
Exchange price (in dollars per share)	$ 92.55
Shares related to the Notes included in the computation for diluted earnings per share (in shares)	226,527	0
Series A Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Exchangeable preferred operating partnership units settled in cash, minimum	$ 101,700,000
Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per common share (in shares)	0	40,956

Earnings Per Common Share - Sch

Earnings Per Common Share - Schedule of Antidilutive Shares Excluded from Computation of Earnings Per Share (Detail) - shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Equivalent Shares (if converted)	1,649,282	1,945,123
Series B Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Equivalent Shares (if converted)	436,254	498,183
Series C Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Equivalent Shares (if converted)	129,763	352,385
Series D Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Equivalent Shares (if converted)	1,083,265	1,094,555

Earnings Per Common Share - S_2

Earnings Per Common Share - Schedule of Computation of Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Class of Stock [Line Items]
Net income attributable to common stockholders	$ 94,770	$ 88,256
Earnings and dividends allocated to participating securities	(167)	(178)
Earnings for basic computations	94,603	88,078
Earnings and dividends allocated to participating securities	0	178
Income allocated to noncontrolling interest - Preferred Operating Partnership Units and Operating Partnership Units	5,429	4,941
Fixed component of income allocated to noncontrolling interest - Preferred Operating Partnership (Series A Units)	(572)	(572)
Net income for diluted computations	$ 99,460	$ 92,625
Weighted average common shares outstanding:
Average number of common shares outstanding - basic (in shares)	127,037,247	125,772,439
OP Units (in shares)	5,960,981	5,663,370
Shares related to exchangeable senior notes and dilutive stock options (in shares)	416,008	371,271
Average number of common shares outstanding - diluted (in shares)	134,289,716	132,682,560
Earnings per common share
Basic (in dollars per share)	$ 0.74	$ 0.70
Diluted (in dollars per share)	$ 0.74	$ 0.70
Series A Units
Weighted average common shares outstanding:
Preferred series units (in shares)	875,480	875,480

Store Acquisitions and Dispos_3

Store Acquisitions and Dispositions - Schedule of Operating Properties Acquired (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)store	Mar. 31, 2018USD ($)store
Real Estate [Abstract]
Number of Stores | store	14	5
Total Consideration Paid	$ 223,740	$ 70,787
Cash Paid	202,890	70,171
Loan Assumed	17,157	0
Investments in Real Estate Ventures	2,780	489
Net Liabilities/ (Assets) Assumed	913	127
Real estate assets	$ 223,740	$ 70,787
Number of stores acquired, previously held noncontrolling interest | store	12	1

Investments in Unconsolidated_3

Investments in Unconsolidated Real Estate Ventures - Schedule of Investments in Unconsolidated Real Estate Ventures (Details) $ in Thousands	1 Months Ended	3 Months Ended
	Jan. 31, 2019USD ($)store	Mar. 31, 2019USD ($)propertystore	Mar. 31, 2018USD ($)store	Jan. 01, 2019	Dec. 31, 2018USD ($)	Jan. 01, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Number of Stores | store		14	5
Cash Paid		$ 202,890	$ 70,171
Number of Stores | property		224
Investment balance		$ 116,459			$ 80,129
PRISA Self Storage LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		85
Equity Ownership %		4.00%
Excess Profit %		4.00%
Investment balance		$ 9,292			9,334
Storage Portfolio II JV LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		36
Equity Ownership %		10.00%
Excess Profit %		30.00%
Investment balance		$ (4,539)			(4,233)
Storage Portfolio I LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		24
Equity Ownership %		34.00%				34.00%	25.00%
Excess Profit %		49.00%				49.00%	40.00%
Investment balance		$ (38,186)			(38,129)
VRS Self Storage, LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		16
Equity Ownership %		45.00%
Excess Profit %		54.00%
Investment balance		$ 18,002			18,281
Extra Space Northern Properties Six LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		10
Equity Ownership %		10.00%
Excess Profit %		35.00%
Investment balance		$ (1,793)			(1,700)
WICNN JV LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		9
Equity Ownership %		10.00%
Excess Profit %		25.00%
Investment balance		$ 32,859			26,885
Alan Jathoo JV LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		9
Equity Ownership %		10.00%
Excess Profit %		10.00%
Investment balance		$ 8,132			8,180
ESS Bristol Investments LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		8
Equity Ownership %		10.00%
Excess Profit %		28.00%
Investment balance		$ 3,025			2,331
GFN JV, LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		5
Equity Ownership %		10.00%
Excess Profit %		25.00%
Investment balance		$ 12,429			10,586
Extra Space West Two LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		0
Equity Ownership %		5.00%
Excess Profit %		40.00%
Investment balance		$ 0			3,818
Extra Space West One LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		0
Equity Ownership %		5.00%
Excess Profit %		40.00%
Investment balance		$ 0			(1,038)
Other minority owned stores
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		22
Investment balance		$ 77,238			$ 45,814
Other minority owned stores | Minimum
Schedule of Equity Method Investments [Line Items]
Equity Ownership %		10.00%
Excess Profit %		19.00%
Other minority owned stores | Maximum
Schedule of Equity Method Investments [Line Items]
Equity Ownership %		50.00%
Excess Profit %		50.00%
Extra Space West One and Two LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | store	12
Cash Paid	$ 172,505
Equity Ownership %				100.00%
Percentage interest purchased	95.00%

Investments in Unconsolidated_4

Investments in Unconsolidated Real Estate Ventures - Narrative (Details) $ in Thousands	Feb. 02, 2018USD ($)	Mar. 31, 2019USD ($)store	Jan. 01, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Contributions to joint ventures | $		$ 40,843
Number of operating stores acquired by joint ventures | store		1
Number of stores acquired at the issuance of certificate of occupancy | store		6
Storage Portfolio I LLC
Schedule of Equity Method Investments [Line Items]
Equity method ownership percentage		34.00%	34.00%	25.00%
Excess profit participation percentage		49.00%	49.00%	40.00%
Financing distribution | $	$ 47,944

Variable Interests - Additional

Variable Interests - Additional Information (Detail) joint_venture in Thousands, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019USD ($)joint_venturesubsidiary	Mar. 31, 2018USD ($)	Dec. 31, 2018USD ($)
Variable Interest Entity [Line Items]
Number of wholly-owned unconsolidated subsidiaries | subsidiary	3
Repayments of debt	$ 30,928	$ 0
Number of interests in consolidated VIE joint ventures | joint_venture	0
Notes payable to Trusts | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Repayments of debt	$ 30,928		$ 88,662
Notes payable to Trusts			$ 30,928

Derivatives - Additional Inform

Derivatives - Additional Information (Detail) $ in Thousands	Mar. 31, 2019USD ($)derivative
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Estimated amount of unrealized gains (losses) expected to be reclassified as interest expense in next fiscal year	$ 13,649
Number of derivative financial instruments | derivative	28
Combined notional amount	$ 2,287,824
Fair value, net liability position	9,889
Contingent cash settlement value	$ 9,889

Derivatives - Schedule of Balan

Derivatives - Schedule of Balance Sheet Classification and Fair Value of Entity's Derivative Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Other assets
Derivative [Line Items]
Other assets	$ 25,908	$ 42,324
Other liabilities
Derivative [Line Items]
Other liabilities	$ 9,307	$ 2,131

Derivatives - Schedule of Infor

Derivatives - Schedule of Information Relating to Gain (Loss) Recognized on Swap Agreements (Detail) - Swap Agreements - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Derivative [Line Items]
Gain (loss) recognized in OCI	$ (19,576)	$ 23,317
Gain reclassified from OCI	$ 4,462	$ 240

Exchangeable Senior Notes - Add

Exchangeable Senior Notes - Additional Information (Detail)	Jun. 21, 2013USD ($)	Sep. 30, 2015USD ($)	Mar. 31, 2019USD ($)day	Mar. 31, 2018USD ($)
Debt Instrument [Line Items]
Total consideration paid for repurchase			$ 225,020,000	$ 168,204,000
Exchangeable Senior Notes 3.125% due 2035 (the 2015 Notes)
Debt Instrument [Line Items]
Principal amount of notes issued		$ 575,000,000
Debt stated interest rate		3.125%	3.125%
Related debt issuance costs		$ 11,992,000
Underwriting fee percentage		2.00%
Amortization period		5 years
Conversion ratio			0.01081
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%
Effective interest rate on the liability component			4.00%
Exchangeable Senior Notes 3.125% due 2035 (the 2015 Notes) | Minimum
Debt Instrument [Line Items]
Number of days of written notice to holders of notes required for redemption		30 days
Exchangeable Senior Notes 3.125% due 2035 (the 2015 Notes) | Maximum
Debt Instrument [Line Items]
Number of days of written notice to holders of notes required for redemption		60 days
Exchangeable Senior Notes 2.375% due 2033 (the 2013 Notes)
Debt Instrument [Line Items]
Principal amount of notes issued	$ 250,000,000
Debt stated interest rate	2.375%		2.375%
Related debt issuance costs	$ 1,672,000
Notes exchange, threshold percentage			130.00%
Notes exchange, threshold trading days | day			20
Notes exchange, threshold consecutive trading days | day			30
Discount rate	1.50%
Unamortized cash discount	$ 3,750,000
Amortization period	5 years
Effective interest rate on the liability component			4.00%
Principal amount repurchased				37,704,000
Total consideration paid for repurchase				$ 58,464,000

Exchangeable Senior Notes - Sch

Exchangeable Senior Notes - Schedule of Information about Total Carrying Amounts of Equity Components, Principal Amounts of Liability Components, Unamortized Discounts and Net Carrying Amounts for Notes (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2015
Debt Instrument [Line Items]
Principal amount of liability component	$ 564,136	$ 562,374
Exchangeable Senior Notes 3.125% due 2035 (the 2015 Notes)
Debt Instrument [Line Items]
Principal amount of liability component	575,000
Unamortized debt issuance costs			$ (11,992)
Senior Notes | Exchangeable Senior Notes 3.125% due 2035 (the 2015 Notes)
Debt Instrument [Line Items]
Carrying amount of equity component	22,597	22,597
Principal amount of liability component	575,000	575,000
Unamortized discount - equity component	(7,255)	(8,417)
Unamortized debt issuance costs	(3,609)	(4,209)
Net carrying amount of liability components	$ 564,136	$ 562,374

Exchangeable Senior Notes - Sum

Exchangeable Senior Notes - Summary of Amount of Interest Cost Recognized Relating to Contractual Interest Rates and Amortization of Discounts on Liability Components of Notes (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Debt Disclosure [Abstract]
Contractual interest	$ 4,492	$ 4,561
Amortization of discount	1,162	1,209
Total interest expense recognized	$ 5,654	$ 5,770

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - At the Market Equity Distribution Agreement $ in Thousands	May 06, 2016USD ($)sales_agent	Mar. 31, 2019USD ($)shares
Class of Stock [Line Items]
Aggregate offering price of common shares	$ 400,000
Number of sales agents | sales_agent	5
Shares, issued (in shares) | shares		0
Value of stock available for issuance under ATM		$ 257,929

Noncontrolling Interest Repre_2

Noncontrolling Interest Represented by Preferred Operating Partnership Units (Details) - USD ($)	Apr. 25, 2019	Dec. 01, 2018	Apr. 18, 2017	Jun. 25, 2007	Dec. 31, 2014	Oct. 31, 2014	Jun. 30, 2007	Mar. 31, 2019	Dec. 31, 2018
Noncontrolling Interest [Line Items]
Note receivable from noncontrolling interest represented by Preferred Operating Partnership units								$ 108,644,000	$ 108,644,000
Series A Units
Noncontrolling Interest [Line Items]
Fixed priority return on preferred OP units, amount						$ 101,700,000
Fixed priority return on preferred OP units, stated return rate			2.30%				5.00%
Fixed priority return on preferred OP units, liquidation value							$ 115,000,000
Preferred units outstanding (in units)						875,480
Series B Units
Noncontrolling Interest [Line Items]
Preferred units outstanding (in units)								1,676,087
Liquidation value (in dollars per share)								$ 25
Fixed liquidation value								$ 41,902,000
Annual rate of return percentage								6.00%
Series C Units
Noncontrolling Interest [Line Items]
Note receivable from noncontrolling interest represented by Preferred Operating Partnership units					$ 20,230,000			$ 19,735,000
Preferred units outstanding (in units)								296,020
Note receivable interest rate					5.00%
Liquidation value (in dollars per share)								$ 42.1
Fixed liquidation value								$ 12,462,000
Quarterly distribution per preferred OP unit payable above quarterly distribution for common OP Unit (in dollars per share)								$ 0.18
Period from date of issuance after which preferred OP units will become redeemable at the option of the holder								1 year
Preferred OP units conversion ratio (in shares)								0.9145
Units converted (in units)		407,996
Series D Units
Noncontrolling Interest [Line Items]
Preferred units outstanding (in units)								4,620,445
Liquidation value (in dollars per share)								$ 25
Fixed liquidation value								$ 115,511,000
Units issued								$ 23,447,000
Series D Units | Minimum
Noncontrolling Interest [Line Items]
Annual rate of return percentage								3.00%
Series D Units | Maximum
Noncontrolling Interest [Line Items]
Annual rate of return percentage								5.00%
Operating Partnership Holders of A Units | Series A Units
Noncontrolling Interest [Line Items]
Note receivable from noncontrolling interest represented by Preferred Operating Partnership units				$ 100,000,000
Maximum number of preferred OP units converted prior to the maturity date of the loan (in units)						114,500
Note receivable interest rate			2.10%	4.90%
Extra Space Storage LP [Member] | Series D Units
Noncontrolling Interest [Line Items]
Units issued (in units)								937,924
Operating Partnership
Noncontrolling Interest [Line Items]
Issuance of units upon conversion (in units)		373,113
Note receivable, reduction of noncontrolling interests								$ 11,091,000
Series C Preferred Operating Partnership
Noncontrolling Interest [Line Items]
Note receivable, reduction of noncontrolling interests								$ 8,644,000
Subsequent Event | Series C Units
Noncontrolling Interest [Line Items]
Units converted (in units)	296,020
Subsequent Event | Operating Partnership
Noncontrolling Interest [Line Items]
Issuance of units upon conversion (in units)	270,710

Noncontrolling Interest in Op_3

Noncontrolling Interest in Operating Partnership - Additional Information (Details) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)propertyjoint_venturestore$ / sharesshares
Noncontrolling Interest [Line Items]
Period used as a denomination to determine the average closing price of common stock	10 days
Ten day average closing stock price (in dollars per share) | $ / shares	$ 100.76
OP units outstanding (in units) | shares	5,908,750
Consideration to be paid on redemption of common OP units | $	$ 595,366
Common Stock
Noncontrolling Interest [Line Items]
OP units conversion ratio	1
Other noncontrolling interests
Noncontrolling Interest [Line Items]
Number of consolidated joint ventures | joint_venture	2
Operating Partnership
Noncontrolling Interest [Line Items]
Ownership interest held by entity	90.50%
Ownership percentage in joint venture by joint venture partner	9.50%
Joint Venture 1
Noncontrolling Interest [Line Items]
Number of operating stores owned | store	2
Joint Venture 2 | Other noncontrolling interests
Noncontrolling Interest [Line Items]
Number of operating stores owned	1
Number of development stores owned	1
Minimum | Other noncontrolling interests
Noncontrolling Interest [Line Items]
Ownership percentage in joint venture by joint venture partner	5.00%
Maximum | Other noncontrolling interests
Noncontrolling Interest [Line Items]
Ownership percentage in joint venture by joint venture partner	20.00%

Noncontrolling Interest in Op_4

Noncontrolling Interest in Operating Partnership - Schedule of OP Unit Activity (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 31, 2018
Noncontrolling Interest [Abstract]
OP Units redeemed for common stock (in units)	85,501	0
OP Units redeemed for cash (in units)	0	30,000
Cash paid for OP Units redeemed	$ 0	$ 2,558

Leases - Lease Costs (Details)

Leases - Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Finance lease cost:
Amortization of finance lease right-of-use assets	$ 42
Interest expense related to finance lease liabilities	70
Operating lease cost	2,079
Variable lease cost	912
Short-term lease cost	55
Total lease cost	3,158
Cash paid for amounts included in the measurement of lease liabilities
Operating cash outflows for finance lease payments	57
Operating cash outflows for operating lease payments	3,267
Total cash paid for lease liability measurement	3,324
Right-of-use assets obtained in exchange for new operating lease liabilities	95,506	$ 0
Right-of-use assets obtained in exchange for new finance lease liabilities	$ 8,050
Weighted average remaining lease term - operating leases	23 years 8 months 13 days
Weighted average remaining lease term - finance leases	72 years 6 months
Weighted average discount rate - operating leases	4.05%
Weighted average discount rate - finance leases	4.25%

Leases - Undiscounted Cash Flow

Leases - Undiscounted Cash Flows on an Annual Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Operating
Year 1	$ 8,281
Year 2	8,353
Year 3	8,264
Year 4	7,898
Year 5	7,828
Thereafter	130,052
Total	170,676
Present value adjustments	(67,098)
Lease liabilities	103,578	$ 0
Finance
Year 1	232
Year 2	232
Year 3	241
Year 4	255
Year 5	255
Thereafter	35,062
Total	36,277
Present value adjustments	(31,484)
Lease liabilities	4,793
Total
Year 1	8,513
Year 2	8,585
Year 3	8,505
Year 4	8,153
Year 5	8,083
Thereafter	165,114
Total	206,953
Present value adjustments	(98,582)
Lease liabilities	$ 108,371

Leases - Narrative (Details)

Leases - Narrative (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)leaseextension	Jan. 01, 2019USD ($)	Dec. 31, 2018USD ($)
Lessee, Lease, Description [Line Items]
Operating lease liabilities | $	$ 103,578		$ 0
Operating lease right-of-use assets | $	$ 94,198		$ 0
Store leases
Lessee, Lease, Description [Line Items]
Number of leases | lease	22
Store leases | Minimum
Lessee, Lease, Description [Line Items]
Operating and finance lease, original lease term	10 years
Operating and finance lease, extension term	5 years
Store leases | Maximum
Lessee, Lease, Description [Line Items]
Operating and finance lease, original lease term	67 years
Operating and finance lease, extension term	35 years
Corporate offices and call center leases | Minimum
Lessee, Lease, Description [Line Items]
Operating lease, original lease term	5 years 4 months
Corporate offices and call center leases | Maximum
Lessee, Lease, Description [Line Items]
Operating lease, original lease term	12 years 1 month
Regional office leases
Lessee, Lease, Description [Line Items]
Number of leases | lease	12
Operating lease, number of options to extend | extension	5
Operating lease, extension term	3 years
Regional office leases | Minimum
Lessee, Lease, Description [Line Items]
Operating lease, original lease term	3 years
Regional office leases | Maximum
Lessee, Lease, Description [Line Items]
Operating lease, original lease term	5 years
District office leases
Lessee, Lease, Description [Line Items]
Operating lease, original lease term	12 months
New Jersey store lease
Lessee, Lease, Description [Line Items]
Lease not yet commenced, lease term	75 years
Lease not yet commenced, number of extension options | extension	3
Lease not yet commenced, term of extension options	10 years
California store lease
Lessee, Lease, Description [Line Items]
Lease not yet commenced, lease term	15 years
California store lease | Lease option one
Lessee, Lease, Description [Line Items]
Lease not yet commenced, number of extension options | extension	3
Lease not yet commenced, term of extension options	10 years
California store lease | Lease option two
Lessee, Lease, Description [Line Items]
Lease not yet commenced, number of extension options | extension	1
Lease not yet commenced, term of extension options	5 years
ASU 2016-02
Lessee, Lease, Description [Line Items]
Operating lease liabilities | $		$ 104,863
Operating lease right-of-use assets | $		$ 95,506

Segment Information - Additiona

Segment Information - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2019segment
Segment Reporting [Abstract]
Number of reportable segments	2

Segment Information - Schedule

Segment Information - Schedule of Financial Information of Business Segments (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Revenues:	$ 311,546	$ 285,485
Operating expenses:	163,069	151,573
Income from operations	148,477	133,912
Management fees and other income	10,746	10,565
General and administrative expense	(22,678)	(21,464)
Depreciation and amortization expense	(54,659)	(51,749)
Interest expense	(47,360)	(40,966)
Non-cash interest expense related to amortization of discount on equity component of exchangeable senior notes	(1,162)	(1,209)
Interest income	1,388	1,438
Equity in earnings of unconsolidated real estate ventures	2,630	3,597
Income tax expense	(1,813)	(1,342)
Net income	102,160	95,430
Operating Segments
Segment Reporting Information [Line Items]
Revenues:	300,800	274,920
Operating expenses:	85,732	78,360
Income from operations	215,068	196,560
Operating Segments | Self-Storage Operations
Segment Reporting Information [Line Items]
Revenues:	271,003	247,886
Operating expenses:	78,765	72,753
Income from operations	192,238	175,133
Operating Segments | Tenant Reinsurance
Segment Reporting Information [Line Items]
Revenues:	29,797	27,034
Operating expenses:	6,967	5,607
Income from operations	$ 22,830	$ 21,427

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Thousands	Mar. 31, 2019USD ($)store
Commitment To Acquire Retail Space
Other Commitments [Line Items]
Number of real estate properties to be acquired	6
Purchase price | $	$ 67,028
Commitment To Acquire Retail Space, Closing In 2019
Other Commitments [Line Items]
Purchase price | $	$ 31,600
Number of stores scheduled to be closed	3
Commitment To Acquire Retail Space, Closing in 2020
Other Commitments [Line Items]
Purchase price | $	$ 35,428
Number of stores scheduled to be closed	3
Commitment To Acquire Retail Space With Joint Venture Partners
Other Commitments [Line Items]
Number of real estate properties to be acquired	6
Purchase price | $	$ 25,346
Commitment To Acquire Retail Space With Joint Venture Partners, Scheduled To Close in 2019
Other Commitments [Line Items]
Number of stores scheduled to be closed	5

Subsequent Events (Details)

Subsequent Events (Details) $ in Thousands	Apr. 25, 2019shares	Dec. 01, 2018shares	May 07, 2019USD ($)store	Mar. 31, 2019USD ($)	Mar. 31, 2018USD ($)
Subsequent Event [Line Items]
Proceeds from sale of real estate assets | $				$ 0	$ 753
Series C Units
Subsequent Event [Line Items]
Units converted (in units)		407,996
Operating Partnership
Subsequent Event [Line Items]
Issuance of units upon conversion (in units)		373,113
Subsequent Event
Subsequent Event [Line Items]
Number of stores sold | store			1
Proceeds from sale of real estate assets | $			$ 11,781
Gain on sale of real estate assets | $			$ 1,200
Subsequent Event | Series C Units
Subsequent Event [Line Items]
Units converted (in units)	296,020
Subsequent Event | Operating Partnership
Subsequent Event [Line Items]
Issuance of units upon conversion (in units)	270,710