Extra Space Storage (EXR) 10-Q 8 May 20 2020 Q1 Quarterly report Financial data

Cover

Cover - shares	3 Months Ended
	Mar. 31, 2020	Apr. 30, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2020
Document Transition Report	false
Entity File Number	001-32269
Entity Registrant Name	EXTRA SPACE STORAGE INC.
Entity Central Index Key	0001289490
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Entity Incorporation, State or Country Code	MD
Entity Tax Identification Number	20-1076777
Entity Address, Address Line One	2795 East Cottonwood Parkway, Suite 300
Entity Address, City or Town	Salt Lake City
Entity Address, State or Province	UT
Entity Address, Postal Zip Code	84121
City Area Code	801
Local Phone Number	365-4600
Title of 12(b) Security	Common Stock, $0.01 par value
Trading Symbol	EXR
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		129,086,589

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Assets:
Real estate assets, net	$ 7,689,621	$ 7,696,864
Real estate assets - operating lease right-of-use assets	259,681	264,643
Investments in unconsolidated real estate entities	342,404	338,054
Cash and cash equivalents	93,297	65,746
Restricted cash	4,633	4,987
Other assets, net	159,850	162,083
Total assets	8,549,486	8,532,377
Liabilities, Noncontrolling Interests and Equity:
Notes payable, net	4,310,476	4,318,973
Exchangeable senior notes, net	571,321	569,513
Revolving lines of credit	244,000	158,000
Operating lease liabilities	270,174	274,783
Cash distributions in unconsolidated real estate ventures	45,712	45,264
Accounts payable and accrued expenses	116,069	111,382
Other liabilities	217,104	132,768
Total liabilities	5,774,856	5,610,683
Commitments and contingencies
Extra Space Storage Inc. stockholders' equity:
Preferred Stock, Value, Issued	0	0
Common Stock, Value, Issued	1,290	1,295
Additional paid-in capital	2,872,933	2,868,681
Accumulated other comprehensive income (loss)	(113,840)	(28,966)
Accumulated deficit	(362,264)	(301,049)
Total Extra Space Storage Inc. stockholders' equity	2,398,119	2,539,961
Noncontrolling interest represented by Preferred Operating Partnership units, net	175,319	175,948
Noncontrolling interests in Operating Partnership, net and other noncontrolling interests	201,192	205,785
Total noncontrolling interests and equity	2,774,630	2,921,694
Total liabilities, noncontrolling interests and equity	$ 8,549,486	$ 8,532,377

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Preferred Stock, Par or Stated Value 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 or Stated Value Per Share	$ 0.01	$ 0.01
Common stock, authorized (in shares)	500,000,000	500,000,000
Common stock, issued (in shares)	129,038,907	129,534,407
Common stock, outstanding (in shares)	129,038,907	129,534,407

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenues:
Property rental	$ 286,703	$ 271,003
Tenant reinsurance	33,613	29,797
Management fees and other income	12,136	10,746
Total revenues	332,452	311,546
Expenses:
Property operations	90,297	78,765
Tenant reinsurance	6,678	6,967
General and administrative	23,011	22,678
Depreciation and amortization	55,275	54,659
Total expenses	175,261	163,069
Income from operations	157,191	148,477
Interest expense	(44,358)	(47,360)
Non-cash interest expense related to amortization of discount on equity component of exchangeable senior notes	(1,209)	(1,162)
Interest income	1,674	1,388
Income before equity in earnings of unconsolidated real estate entities and income tax expense	113,298	101,343
Equity in earnings and dividend income from unconsolidated real estate entities	5,043	2,630
Income tax expense	(2,179)	(1,813)
Net income	116,162	102,160
Net income allocated to Preferred Operating Partnership noncontrolling interests	(3,111)	(3,163)
Net income allocated to Operating Partnership and other noncontrolling interests	(4,872)	(4,227)
Net income attributable to common stockholders	$ 108,179	$ 94,770
Earnings per common share
Basic (in dollars per share)	$ 0.84	$ 0.74
Diluted (in dollars per share)	$ 0.83	$ 0.74
Weighted average number of shares
Basic (in shares)	129,288,629	127,037,247
Diluted (in shares)	137,139,560	134,289,716
Cash dividends paid per common share (in dollars per share)	$ 0.90	$ 0.86

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 116,162	$ 102,160
Other comprehensive income (loss):
Change in fair value of interest rate swaps	(89,244)	(23,993)
Total comprehensive income	26,918	78,167
Less: comprehensive income attributable to noncontrolling interests	3,613	6,240
Comprehensive income attributable to common stockholders	$ 23,305	$ 71,927

Condensed Consolidated Statem_3

Condensed Consolidated Statement of Noncontrolling Interests and Equity - USD ($) $ in Thousands	Total	Noncontrolling Interest - Preferred Operating Partnership	Noncontrolling Interest - Operating Partnership	Noncontrolling Interest - Other	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income	Accumulated Deficit
Balance, beginning of period at Dec. 31, 2018	$ 2,785,422	$ 153,096	$ 218,362	$ 240	$ 1,271	$ 2,640,705	$ 34,650	$ (262,902)
Balance, beginning of period (in shares) at Dec. 31, 2018					127,103,750
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon the exercise of options	1,757				$ 3	1,754
Issuance of common stock upon the exercise of options (in shares)					169,021
Restricted stock grants issued	0
Restricted stock grants issued (in shares)					35,022
Restricted stock grants cancelled	0
Restricted stock grants cancelled (in shares)					(1,244)
Compensation expense related to stock-based awards	2,954					2,954
Redemption of Operating Partnership units for stock	0		(3,310)			3,310
Redemption of Operating Partnership units (in shares)					85,501
Issuance of Preferred D Units in the Operating Partnership in conjunction with acquisitions	23,447	23,447
Net income	102,160	3,164	4,235	(9)				94,770
Other comprehensive income	(23,993)	(147)	(1,003)				(22,843)
Distributions to Operating Partnership units held by noncontrolling interests	(8,412)	(3,296)	(5,116)
Dividends paid on common stock	(109,523)							(109,523)
Balance, end of period at Mar. 31, 2019	2,773,812	176,264	213,168	231	$ 1,274	2,648,723	11,807	(277,655)
Balance, end of period (in shares) at Mar. 31, 2019					127,392,050
Balance, beginning of period at Dec. 31, 2019	$ 2,921,694	175,948	205,419	366	$ 1,295	2,868,681	(28,966)	(301,049)
Balance, beginning of period (in shares) at Dec. 31, 2019	129,534,407				129,534,407
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon the exercise of options	$ 944				$ 1	943
Issuance of common stock upon the exercise of options (in shares)					77,400
Issuance of common stock in connection with share based compensation	2,980				$ 1	2,979
Issuance of common stock in connection with share based compensation (in shares)					73,602
Restricted stock grants cancelled	0
Restricted stock grants cancelled (in shares)					(1,767)
Buyback of common stock, net of offering costs	(52,204)				$ (7)			(52,197)
Buyback of common stock, net of offering costs (in shares)					(653,597)
Redemption of Operating Partnership units for stock	0		(330)			330
Redemption of Operating Partnership units (in shares)					8,862
Net income	116,162	3,112	4,877	(6)				108,179
Other comprehensive income	(89,244)	(563)	(3,807)				(84,874)
Distributions to Operating Partnership units held by noncontrolling interests	(8,505)	(3,178)	(5,327)
Dividends paid on common stock	(117,197)							(117,197)
Balance, end of period at Mar. 31, 2020	$ 2,774,630	$ 175,319	$ 200,832	$ 360	$ 1,290	$ 2,872,933	$ (113,840)	$ (362,264)
Balance, end of period (in shares) at Mar. 31, 2020	129,038,907				129,038,907

Condensed Consolidated Statem_4

Condensed Consolidated Statement of Noncontrolling Interests and Equity (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Stockholders' Equity [Abstract]
Dividends paid on common stock (in dollars per share)	$ 0.90	$ 0.86

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net income	$ 116,162	$ 102,160
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	55,275	54,659
Amortization of deferred financing costs	2,830	3,034
Non-cash interest expense related to amortization of discount on equity component of exchangeable senior notes	1,209	1,162
Non-cash lease expense	353	0
Compensation expense related to stock-based awards	2,980	2,954
Distributions from unconsolidated real estate ventures in excess of earnings	2,539	1,732
Changes in operating assets and liabilities:
Other assets	2,490	(305)
Accounts payable and accrued expenses	3,727	6,418
Other liabilities	1,691	(2,475)
Net cash provided by operating activities	189,256	169,339
Cash flows from investing activities:
Acquisition of real estate assets	(30,164)	(212,552)
Development and redevelopment of real estate assets	(15,373)	(15,846)
Investment in unconsolidated real estate entities	(6,441)	(17,395)
Issuance of notes receivable	(7,500)	0
Purchase of equipment and fixtures	(1,095)	(1,182)
Net cash used in investing activities	(60,573)	(246,975)
Cash flows from financing activities:
Proceeds from notes payable and revolving lines of credit	268,000	424,000
Principal payments on notes payable and revolving lines of credit	(192,508)	(225,020)
Principal payments on notes payable to trusts	0	(30,928)
Deferred financing costs	(16)	(100)
Net proceeds from exercise of stock options	944	1,757
Repurchase of common stock	(52,204)	0
Dividends paid on common stock	(117,197)	(109,523)
Distributions to noncontrolling interests	(8,505)	(8,412)
Net cash provided by (used in) financing activities	(101,486)	51,774
Net increase (decrease) in cash, cash equivalents, and restricted cash	27,197	(25,862)
Cash, cash equivalents, and restricted cash, beginning of the period	70,733	72,690
Cash, cash equivalents, and restricted cash, end of the period	97,930	46,828
Supplemental schedule of cash flow information
Interest paid	41,013	45,165
Income taxes paid	976	(177)
Redemption of Operating Partnership units held by noncontrolling interests for common stock
Noncontrolling interests in Operating Partnership	(330)	(3,310)
Common stock and paid-in capital	330	3,310
Establishment of operating lease right of use assets and lease liabilities
Real estate assets - operating lease right-of-use assets	0	95,506
Operating lease liabilities	0	(104,863)
Accounts payable and accrued expenses	0	9,357
Acquisitions of real estate assets
Real estate assets, net	0	19,937
Notes payable assumed	0	(17,157)
Investment in unconsolidated real estate ventures	0	(2,780)
Accrued construction costs and capital expenditures
Acquisition of real estate assets	960	780
Accounts payable and accrued expenses	(960)	(780)
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	0	23,447
Value of Preferred Operating Partnership units issued	$ 0	$ (23,447)

Organization

Organization	3 Months Ended
	Mar. 31, 2020
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, 2020, the Company had direct and indirect equity interests in 1,176 stores. In addition, the Company managed 676 stores for third parties, bringing the total number of stores which it owns and/or manages to 1,852. 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, 2020
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, 2020 are not necessarily indicative of results that may be expected for the year ending December 31, 2020. The condensed consolidated balance sheet as of December 31, 2019 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, 2019, as filed with the Securities and Exchange Commission. Recently Issued Accounting Standards In June 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("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. 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), and not within the scope of ASU 2016-13. This new standard became effective for the Company on January 1, 2020. The adoption of this standard by the Company did not have a material impact on the Company's consolidated financial statements. In March 2020, the FASB issued ASU 2020-04, " Reference Rate Reform (Topic 848)

Fair Value Disclosures

Fair Value Disclosures	3 Months Ended
	Mar. 31, 2020
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, 2020, 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, 2020, 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 liabilities - Cash flow hedge swap agreements $ — $ 113,986 $ — 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, 2020 or December 31, 2019. 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, 2020, the Company had one parcel of land classified as held for sale which is included in real estate assets, net. The estimated fair value less selling costs for this asset is greater than the carrying value of the asset, 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, 2020 and December 31, 2019 approximate fair value. Restricted cash is comprised of escrowed funds deposited with financial institutions located throughout the United States relating to earnest money deposits on potential acquisitions, real estate taxes, loan collateral, operating reserves and insurance and capital expenditures. The fair values of the Company’s notes receivable from Preferred and Common Operating Partnership unit holders, were based on the discounted estimated future cash flows of the notes (categorized within Level 3 of the fair value hierarchy); the discount rate used approximated the current market rate for loans with similar maturities and credit quality. The fair values of the Company’s fixed-rate notes payable 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, 2020 December 31, 2019 Fair Carrying Fair Carrying Notes receivable from Preferred and Common Operating Partnership unit holders $ 119,016 $ 118,524 $ 116,184 $ 118,524 Fixed rate notes payable $ 3,599,824 $ 3,460,253 $ 3,511,151 $ 3,417,928 Exchangeable senior notes $ 635,375 $ 575,000 $ 673,831 $ 575,000

Earnings Per Common Share

Earnings Per Common Share	3 Months Ended
	Mar. 31, 2020
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, 2020, and 2019, there were no anti-dilutive options. 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, 2020 and 2019 was $104.13 and $96.05, 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, 2020 2019 Equivalent Shares (if converted) Equivalent Shares (if converted) Series B Units 402,403 436,254 Series C Units (1) — 129,763 Series D Units 1,153,233 1,083,265 1,555,636 1,649,282 (1) The remainder of the Series C Units were converted to OP Units on April 25, 2019. 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, 2020. 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 $91.46 per share as of March 31, 2020, 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 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, 2020 and 2019, 764,703 and 226,527 shares, respectively, related to the 2015 Notes were included in the computation for diluted earnings per share. For the purposes of computing the diluted impact on earnings per share of the potential exchange of Series A Units for common shares upon redemption, where the Company has the option to redeem in cash or shares and where the Company has stated the positive intent and ability to settle at least $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, 2020 2019 Net income attributable to common stockholders $ 108,179 $ 94,770 Earnings and dividends allocated to participating securities (163) (167) Earnings for basic computations 108,016 94,603 Earnings and dividends allocated to participating securities 163 — Income allocated to noncontrolling interest - Preferred Operating Partnership Units and Operating Partnership Units 6,171 5,429 Fixed component of income allocated to noncontrolling interest - Preferred Operating Partnership (Series A Units) (572) (572) Net income for diluted computations $ 113,778 $ 99,460 Weighted average common shares outstanding: Average number of common shares outstanding - basic 129,288,629 127,037,247 OP Units 5,919,705 5,960,981 Series A Units 875,480 875,480 Unvested restricted stock awards included for treasury stock method 211,602 — Shares related to exchangeable senior notes and dilutive stock options 844,144 416,008 Average number of common shares outstanding - diluted 137,139,560 134,289,716 Earnings per common share Basic $ 0.84 $ 0.74 Diluted $ 0.83 $ 0.74

Store Acquisitions

Store Acquisitions	3 Months Ended
	Mar. 31, 2020
Real Estate [Abstract]
Store Acquisitions	STORE ACQUISITIONS The following table shows the Company’s acquisitions of stores for the three months ended March 31, 2020 and 2019. 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 2020 2 $ 19,399 $ 19,354 $ — $ — $ 45 $ 19,399 Q1 2019 14 (1) $ 223,740 $ 202,890 $ 17,157 $ 2,780 $ 913 $ 223,740 (1) Store acquisitions during the three months ended March 31, 2019 include the acquisition 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 these acquisitions.

Investments in Unconsolidated R

Investments in Unconsolidated Real Estate Ventures	3 Months Ended
	Mar. 31, 2020
Equity Method Investments and Joint Ventures [Abstract]
Investments in Unconsolidated Real Estate Ventures	INVESTMENTS IN UNCONSOLIDATED REAL ESTATE ENTITIES Investments in unconsolidated real estate entities and cash distributions in unconsolidated real estate ventures represent the Company's interest in preferred stock of SmartStop Self Storage REIT, Inc. ("SmartStop") and the Company's noncontrolling interest in real estate joint ventures that own stores. The Company accounts for its investment in SmartStop preferred stock, which does not have a readily determinable fair value, at the transaction price less impairment, if any. The Company accounts for its investments in joint ventures 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, 2020, the Company contributed a total of $6,441 to its joint ventures for the purchase of one operating store and two 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, 2020 2019 PR EXR Self Storage, LLC 5 25% 40% $ 59,147 $ 59,391 WICNN JV LLC 10 10% 25% 36,445 36,552 VRS Self Storage, LLC 16 45% 54% 17,356 17,639 ESS-NYFL JV LP 11 16% 24% 12,611 13,320 GFN JV, LLC 6 10% 30% 15,576 12,168 PRISA Self Storage LLC 85 4% 4% 9,073 9,133 Alan Jathoo JV LLC 9 10% 10% 7,928 7,977 Storage Portfolio III JV LLC 5 10% 30% 5,832 3,995 ESS Bristol Investments LLC 8 10% 28% 2,914 3,046 Extra Space Northern Properties Six LLC 10 10% 35% (2,228) (2,091) Storage Portfolio II JV LLC 36 10% 30% (4,915) (4,827) Storage Portfolio I LLC 24 34% 49% (38,570) (38,345) Other minority owned stores 19 10-50% 19-50% 25,523 24,832 SmartStop Self Storage REIT, Inc. Preferred Stock (2) n/a n/a n/a 150,000 150,000 Net Investments in and Cash distributions in unconsolidated real estate entities 244 $ 296,692 $ 292,790 (1) Includes pro-rata equity ownership share and promoted interest. (2) In October 2019, the Company invested $150,000 in shares of newly issued convertible preferred stock of SmartStop,with an additional commitment to purchase up to $50,000 of the preferred shares over the 12 months after the original purchase. The dividend rate for the preferred shares is 6.25% per annum, subject to increase after five years. The preferred shares are generally not redeemable for five years, except in the case of a change of control or initial listing of SmartStop. Dividend income from this investment is included on the equity in earnings and dividend income from unconsolidated real estate entities line on the Company's condensed consolidated statements of operations.

Variable Interests

Variable Interests	3 Months Ended
	Mar. 31, 2020
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. In January 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, 2020.

Derivatives

Derivatives	3 Months Ended
	Mar. 31, 2020
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, 2020 and 2019, 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 $32,595 will be reclassified and increase interest expense. The Company held 25 derivative financial instruments which had a total combined notional amount of $2,396,948 as of March 31, 2020. 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, 2020 December 31, 2019 Derivatives designated as hedging instruments: Fair Value Other assets $ — $ 6,214 Other liabilities $ 113,986 $ 31,400 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 (loss) reclassified from OCI For the Three Months Ended March 31, Type 2020 2019 2020 2019 Swap Agreements $ (89,710) $ (19,576) Interest expense $ (563) $ 4,462 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, 2020, 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 $116,411. As of March 31, 2020, the Company had not posted any collateral related to these agreements. If the Company had breached any of these provisions as of March 31, 2020, it could have been required to cash settle its obligations under the agreements at their termination value of $116,411, including accrued interest.

Exchangeable Senior Notes

Exchangeable Senior Notes	3 Months Ended
	Mar. 31, 2020
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, 2020 was approximately 10.93 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, 2020. 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 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 of October 1, 2020. The effective interest rate on the liability components of 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, 2020 December 31, 2019 Carrying amount of equity component $ 22,597 $ 22,597 Principal amount of liability component $ 575,000 $ 575,000 Unamortized discount - equity component (2,466) (3,675) Unamortized debt issuance costs (1,213) (1,812) Net carrying amount of liability component $ 571,321 $ 569,513 The amount of interest cost recognized relating to the contractual interest rate and the amortization of the discount on the liability component of the Notes were as follows for the periods indicated: For the Three Months Ended March 31, 2020 2019 Contractual interest $ 4,492 $ 4,492 Amortization of discount 1,209 1,162 Total interest expense recognized $ 5,701 $ 5,654

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2020
Stockholders' Equity Note [Abstract]
Stockholders' Equity	STOCKHOLDERS’ EQUITY On May 15, 2019, the Company filed its $500,000 "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 nine sales agents. During the three months ended March 31, 2020, the Company sold no shares of common stock under its "at the market" equity program and had $298,621 available for issuance under the equity distribution agreements.

Noncontrolling Interest Represe

Noncontrolling Interest Represented by Preferred Operating Partnership Units	3 Months Ended
	Mar. 31, 2020
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, 2020 and December 31, 2019, 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. As of March 31, 2020 and December 31, 2019, noncontrolling interests in Preferred OP Units were presented net of notes receivable from Preferred OP Unit holders of $100,000 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 June 25, 2007, the Operating Partnership loaned the holder of the Series A Units $100,000. The loan bears interest at 2.1%. 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 ranked 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 had a liquidation value of $42.10 per unit. The Series C Units became redeemable at the option of the holder one year from the date of issuance, which redemption obligation could be satisfied at the Company’s option in cash or shares of its common stock. The Series C Units were 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 expired 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 were shown on the balance sheet net of the loan balance because the borrower under the loan receivable was 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 December 31, 2018, the total outstanding balance of the loan receivable was $19,735, of which $8,644 was shown as a reduction of the noncontrolling interests related to the Series C Units and $11,091 was shown as a reduction of the noncontrolling interests related to the OP Units on the Company's consolidated balance sheets. On April 25, 2019, the remaining 296,020 Series C Units were converted into 270,709 OP Units. The remaining outstanding balance of the loan receivable of $18,524 is shown as a reduction of the noncontrolling interests related to the OP Units as of December 31, 2019 and March 31, 2020. See footnote 12 for further discussion of noncontrolling interests. 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 2019. During the three months ended March 31, 2019, the Operating Partnership issued 1,120,924 Series D Units valued at $28,023 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 $120,086, which represents 4,803,445 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 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 93.8% ownership interest in the Operating Partnership as of March 31, 2020. The remaining ownership interests in the Operating Partnership (including Preferred OP Units) of 6.2% are held by certain former owners of assets acquired by the Operating Partnership. As of March 31, 2020 and December 31, 2019, the noncontrolling interests in the Operating Partnership are shown on the balance sheet net of notes receivable of $18,524 because the borrowers under the loan receivable are also holders of OP Units (Note 11). This loan receivable bears interest at 5.0% per annum and matures on December 15, 2024. 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 ten OP Unit activity is summarized as follows for the periods presented: For the Three Months Ended March 31, 2020 2019 OP Units redeemed for common stock 8,862 85,501 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

Noncontrolling Interest in Oper

Noncontrolling Interest in Operating Partnership and Other Noncontrolling Interests	3 Months Ended
	Mar. 31, 2020
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, 2020 and December 31, 2019, 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. As of March 31, 2020 and December 31, 2019, noncontrolling interests in Preferred OP Units were presented net of notes receivable from Preferred OP Unit holders of $100,000 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 June 25, 2007, the Operating Partnership loaned the holder of the Series A Units $100,000. The loan bears interest at 2.1%. 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 ranked 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 had a liquidation value of $42.10 per unit. The Series C Units became redeemable at the option of the holder one year from the date of issuance, which redemption obligation could be satisfied at the Company’s option in cash or shares of its common stock. The Series C Units were 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 expired 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 were shown on the balance sheet net of the loan balance because the borrower under the loan receivable was 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 December 31, 2018, the total outstanding balance of the loan receivable was $19,735, of which $8,644 was shown as a reduction of the noncontrolling interests related to the Series C Units and $11,091 was shown as a reduction of the noncontrolling interests related to the OP Units on the Company's consolidated balance sheets. On April 25, 2019, the remaining 296,020 Series C Units were converted into 270,709 OP Units. The remaining outstanding balance of the loan receivable of $18,524 is shown as a reduction of the noncontrolling interests related to the OP Units as of December 31, 2019 and March 31, 2020. See footnote 12 for further discussion of noncontrolling interests. 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 2019. During the three months ended March 31, 2019, the Operating Partnership issued 1,120,924 Series D Units valued at $28,023 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 $120,086, which represents 4,803,445 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 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 93.8% ownership interest in the Operating Partnership as of March 31, 2020. The remaining ownership interests in the Operating Partnership (including Preferred OP Units) of 6.2% are held by certain former owners of assets acquired by the Operating Partnership. As of March 31, 2020 and December 31, 2019, the noncontrolling interests in the Operating Partnership are shown on the balance sheet net of notes receivable of $18,524 because the borrowers under the loan receivable are also holders of OP Units (Note 11). This loan receivable bears interest at 5.0% per annum and matures on December 15, 2024. 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 ten OP Unit activity is summarized as follows for the periods presented: For the Three Months Ended March 31, 2020 2019 OP Units redeemed for common stock 8,862 85,501 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

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2020
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. Financial information for the Company’s business segments is set forth below: For the Three Months Ended March 31, 2020 2019 Revenues: Self-Storage Operations $ 286,703 $ 271,003 Tenant Reinsurance 33,613 29,797 Total segment revenues $ 320,316 $ 300,800 Operating expenses: Self-Storage Operations $ 90,297 $ 78,765 Tenant Reinsurance 6,678 6,967 Total segment operating expenses $ 96,975 $ 85,732 Net operating income: Self-Storage Operations $ 196,406 $ 192,238 Tenant Reinsurance 26,935 22,830 Total segment net operating income: $ 223,341 $ 215,068 Other components of net income (loss): Property management fees and other income $ 12,136 $ 10,746 General and administrative expense (23,011) (22,678) Depreciation and amortization expense (55,275) (54,659) Interest expense (44,358) (47,360) Non-cash interest expense related to amortization of discount on equity component of exchangeable senior notes (1,209) (1,162) Interest income 1,674 1,388 Equity in earnings and dividend income from unconsolidated real estate entities 5,043 2,630 Income tax expense (2,179) (1,813) Net income $ 116,162 $ 102,160

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIESAs of March 31, 2020, 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, 2020, the Company was under agreement to acquire three stores at a total purchase price of $20,634. One store is scheduled to close in 2020 and the remaining two stores are expected to close in 2021. Additionally, the Company is under agreement to acquire five stores with joint venture partners, for a total investment of $25,770. Four of these stores are scheduled to close in 2020 and the remaining store is expected to close in 2021. 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, 2020
Subsequent Events [Abstract]
Subsequent Events	SUBSEQUENT EVENTSSubsequent to March 31, 2020, the global economy has continued to be severely impacted by the COVID-19 pandemic. The impact of the COVID-19 pandemic on the U.S. and world economies generally, and on our future results in particular, could be significant and will largely depend on future developments, which are highly uncertain and cannot be predicted. This includes new information which may emerge concerning the severity of COVID-19, the success of actions taken to contain or treat COVID-19 and reactions by consumers, companies, governmental entities and capital markets.

Basis of Presentation (Policies

Basis of Presentation (Policies)	3 Months Ended
	Mar. 31, 2020
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, 2020 are not necessarily indicative of results that may be expected for the year ending December 31, 2020. The condensed consolidated balance sheet as of December 31, 2019 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, 2019, as filed with the Securities and Exchange Commission.
Recently Issued Accounting Standards	Recently Issued Accounting Standards In June 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("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. 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), and not within the scope of ASU 2016-13. This new standard became effective for the Company on January 1, 2020. The adoption of this standard by the Company did not have a material impact on the Company's consolidated financial statements. In March 2020, the FASB issued ASU 2020-04, " Reference Rate Reform (Topic 848)
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, 2020, 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. 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, 2020, the Company had one parcel of land classified as held for sale which is included in real estate assets, net. The estimated fair value less selling costs for this asset is greater than the carrying value of the asset, 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, 2020 and December 31, 2019 approximate fair value. Restricted cash is comprised of escrowed funds deposited with financial institutions located throughout the United States relating to earnest money deposits on potential acquisitions, real estate taxes, loan collateral, operating reserves and insurance and capital expenditures.
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, 2020, and 2019, there were no anti-dilutive options.
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.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.
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 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 of October 1, 2020.

Fair Value Disclosures (Tables)

Fair Value Disclosures (Tables)	3 Months Ended
	Mar. 31, 2020
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, 2020, 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 liabilities - Cash flow hedge swap agreements $ — $ 113,986 $ —
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, 2020 December 31, 2019 Fair Carrying Fair Carrying Notes receivable from Preferred and Common Operating Partnership unit holders $ 119,016 $ 118,524 $ 116,184 $ 118,524 Fixed rate notes payable $ 3,599,824 $ 3,460,253 $ 3,511,151 $ 3,417,928 Exchangeable senior notes $ 635,375 $ 575,000 $ 673,831 $ 575,000

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	3 Months Ended
	Mar. 31, 2020
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, 2020 2019 Equivalent Shares (if converted) Equivalent Shares (if converted) Series B Units 402,403 436,254 Series C Units (1) — 129,763 Series D Units 1,153,233 1,083,265 1,555,636 1,649,282 (1) The remainder of the Series C Units were converted to OP Units on April 25, 2019.
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, 2020 2019 Net income attributable to common stockholders $ 108,179 $ 94,770 Earnings and dividends allocated to participating securities (163) (167) Earnings for basic computations 108,016 94,603 Earnings and dividends allocated to participating securities 163 — Income allocated to noncontrolling interest - Preferred Operating Partnership Units and Operating Partnership Units 6,171 5,429 Fixed component of income allocated to noncontrolling interest - Preferred Operating Partnership (Series A Units) (572) (572) Net income for diluted computations $ 113,778 $ 99,460 Weighted average common shares outstanding: Average number of common shares outstanding - basic 129,288,629 127,037,247 OP Units 5,919,705 5,960,981 Series A Units 875,480 875,480 Unvested restricted stock awards included for treasury stock method 211,602 — Shares related to exchangeable senior notes and dilutive stock options 844,144 416,008 Average number of common shares outstanding - diluted 137,139,560 134,289,716 Earnings per common share Basic $ 0.84 $ 0.74 Diluted $ 0.83 $ 0.74

Store Acquisitions (Tables)

Store Acquisitions (Tables)	3 Months Ended
	Mar. 31, 2020
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, 2020 and 2019. 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 2020 2 $ 19,399 $ 19,354 $ — $ — $ 45 $ 19,399 Q1 2019 14 (1) $ 223,740 $ 202,890 $ 17,157 $ 2,780 $ 913 $ 223,740 (1) Store acquisitions during the three months ended March 31, 2019 include the acquisition 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 these acquisitions.

Investments in Unconsolidated_2

Investments in Unconsolidated Real Estate Ventures - (Tables)	3 Months Ended
	Mar. 31, 2020
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, 2020 2019 PR EXR Self Storage, LLC 5 25% 40% $ 59,147 $ 59,391 WICNN JV LLC 10 10% 25% 36,445 36,552 VRS Self Storage, LLC 16 45% 54% 17,356 17,639 ESS-NYFL JV LP 11 16% 24% 12,611 13,320 GFN JV, LLC 6 10% 30% 15,576 12,168 PRISA Self Storage LLC 85 4% 4% 9,073 9,133 Alan Jathoo JV LLC 9 10% 10% 7,928 7,977 Storage Portfolio III JV LLC 5 10% 30% 5,832 3,995 ESS Bristol Investments LLC 8 10% 28% 2,914 3,046 Extra Space Northern Properties Six LLC 10 10% 35% (2,228) (2,091) Storage Portfolio II JV LLC 36 10% 30% (4,915) (4,827) Storage Portfolio I LLC 24 34% 49% (38,570) (38,345) Other minority owned stores 19 10-50% 19-50% 25,523 24,832 SmartStop Self Storage REIT, Inc. Preferred Stock (2) n/a n/a n/a 150,000 150,000 Net Investments in and Cash distributions in unconsolidated real estate entities 244 $ 296,692 $ 292,790 (1) Includes pro-rata equity ownership share and promoted interest. (2) In October 2019, the Company invested $150,000 in shares of newly issued convertible preferred stock of SmartStop,with an additional commitment to purchase up to $50,000 of the preferred shares over the 12 months after the original purchase. The dividend rate for the preferred shares is 6.25% per annum, subject to increase after five years. The preferred shares are generally not redeemable for five years, except in the case of a change of control or initial listing of SmartStop. Dividend income from this investment is included on the equity in earnings and dividend income from unconsolidated real estate entities line on the Company's condensed consolidated statements of operations.

Derivatives (Tables)

Derivatives (Tables)	3 Months Ended
	Mar. 31, 2020
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, 2020 December 31, 2019 Derivatives designated as hedging instruments: Fair Value Other assets $ — $ 6,214 Other liabilities $ 113,986 $ 31,400
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 (loss) reclassified from OCI For the Three Months Ended March 31, Type 2020 2019 2020 2019 Swap Agreements $ (89,710) $ (19,576) Interest expense $ (563) $ 4,462

Exchangeable Senior Notes (Tabl

Exchangeable Senior Notes (Tables)	3 Months Ended
	Mar. 31, 2020
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, 2020 December 31, 2019 Carrying amount of equity component $ 22,597 $ 22,597 Principal amount of liability component $ 575,000 $ 575,000 Unamortized discount - equity component (2,466) (3,675) Unamortized debt issuance costs (1,213) (1,812) Net carrying amount of liability component $ 571,321 $ 569,513
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 Notes were as follows for the periods indicated: For the Three Months Ended March 31, 2020 2019 Contractual interest $ 4,492 $ 4,492 Amortization of discount 1,209 1,162 Total interest expense recognized $ 5,701 $ 5,654

Noncontrolling Interest in Op_2

Noncontrolling Interest in Operating Partnership and Other Noncontrolling Interests (Tables)	3 Months Ended
	Mar. 31, 2020
Noncontrolling Interest [Abstract]
Redeemable Noncontrolling Interest	OP Unit activity is summarized as follows for the periods presented: For the Three Months Ended March 31, 2020 2019 OP Units redeemed for common stock 8,862 85,501

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2020
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, 2020 2019 Revenues: Self-Storage Operations $ 286,703 $ 271,003 Tenant Reinsurance 33,613 29,797 Total segment revenues $ 320,316 $ 300,800 Operating expenses: Self-Storage Operations $ 90,297 $ 78,765 Tenant Reinsurance 6,678 6,967 Total segment operating expenses $ 96,975 $ 85,732 Net operating income: Self-Storage Operations $ 196,406 $ 192,238 Tenant Reinsurance 26,935 22,830 Total segment net operating income: $ 223,341 $ 215,068 Other components of net income (loss): Property management fees and other income $ 12,136 $ 10,746 General and administrative expense (23,011) (22,678) Depreciation and amortization expense (55,275) (54,659) Interest expense (44,358) (47,360) Non-cash interest expense related to amortization of discount on equity component of exchangeable senior notes (1,209) (1,162) Interest income 1,674 1,388 Equity in earnings and dividend income from unconsolidated real estate entities 5,043 2,630 Income tax expense (2,179) (1,813) Net income $ 116,162 $ 102,160

Organization (Detail)

Organization (Detail)	Mar. 31, 2020storestate
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of operating storage facilities in which the entity has equity interests (in stores)	1,176
Number of stores owned by franchisees and third parties	676
Number of operating stores owned and/or managed	1,852
Number of states in which operating storage facilities are located | state	40

Fair Value Disclosures - Assets

Fair Value Disclosures - Assets and Liabilities on a Recurring Basis (Detail) - Recurring Basis $ in Thousands	Mar. 31, 2020USD ($)
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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 liabilities - Cash flow hedge swap agreements	113,986
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other liabilities - Cash flow hedge swap agreements	$ 0

Fair Value Disclosures - Additi

Fair Value Disclosures - Additional Information (Detail)	Mar. 31, 2020land_parcel
Fair Value Disclosures [Abstract]
Number of parcels of land held-for-sale	1

Fair Value Disclosures - Schedu

Fair Value Disclosures - Schedule of Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Fair Value
Fair Value of Financial Instruments [Line Items]
Notes receivable from Preferred and Common Operating Partnership unit holders	$ 119,016	$ 116,184
Fixed rate notes payable	3,599,824	3,511,151
Exchangeable senior notes	635,375	673,831
Carrying Value
Fair Value of Financial Instruments [Line Items]
Notes receivable from Preferred and Common Operating Partnership unit holders	118,524	118,524
Fixed rate notes payable	3,460,253	3,417,928
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, 2020	Mar. 31, 2019	Dec. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Average share price (in dollars per share)	$ 104.13	$ 96.05
Exchangeable senior notes, net	$ 571,321,000		$ 569,513,000
Exchangeable Senior Notes 3.125% due 2035 (the 2015 Notes)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Exchangeable senior notes, net	$ 575,000,000
Debt stated interest rate	3.125%
Exchange price (in dollars per share)	$ 91.46
Shares related to the Notes included in the computation for diluted earnings per share (in shares)	764,703	226,527
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	0

Earnings Per Common Share - Ant

Earnings Per Common Share - Antidilutive Shares (Detail) - shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Equivalent Shares (if converted)	1,555,636	1,649,282
Series B Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Equivalent Shares (if converted)	402,403	436,254
Series C Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Equivalent Shares (if converted)	0	129,763
Series D Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Equivalent Shares (if converted)	1,153,233	1,083,265

Earnings Per Common Share - Sch

Earnings Per Common Share - Schedule of Computation (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share [Abstract]
Net income attributable to common stockholders	$ 108,179	$ 94,770
Earnings and dividends allocated to participating securities	(163)	(167)
Earnings for basic computations	108,016	94,603
Earnings and dividends allocated to participating securities	163	0
Income allocated to noncontrolling interest - Preferred Operating Partnership Units and Operating Partnership Units	6,171	5,429
Fixed component of income allocated to noncontrolling interest - Preferred Operating Partnership (Series A Units)	(572)	(572)
Net income for diluted computations	$ 113,778	$ 99,460
Weighted average common shares outstanding:
Average number of common shares outstanding - basic (in shares)	129,288,629	127,037,247
OP Units (in shares)	5,919,705	5,960,981
Preferred Units (in shares)	875,480	875,480
Unvested restricted stock awards included for treasury stock method (in shares)	211,602	0
Shares related to exchangeable senior notes and dilutive stock options (in shares)	844,144	416,008
Average number of common shares outstanding - diluted (in shares)	137,139,560	134,289,716
Earnings per common share
Basic (in dollars per share)	$ 0.84	$ 0.74
Diluted (in dollars per share)	$ 0.83	$ 0.74

Store Acquisitions (Detail)

Store Acquisitions (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)store	Mar. 31, 2019USD ($)store
Real Estate [Abstract]
Number of Stores | store	2	14
Total Consideration Paid	$ 19,399	$ 223,740
Cash Paid	19,354	202,890
Loan Assumed	0	17,157
Investments in Real Estate Ventures	0	2,780
Net Liabilities/ (Assets) Assumed	$ 45	$ 913
Number of stores acquired, previously held noncontrolling interest | store		12

Investments in Unconsolidated_3

Investments in Unconsolidated Real Estate Ventures - Narrative (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)store
Equity Method Investments and Joint Ventures [Abstract]
Contributions to joint ventures | $	$ 6,441
Number of operating stores acquired	1
Number of stores acquired at certificate of occupancy	2

Investments in Unconsolidated_4

Investments in Unconsolidated Real Estate Ventures - Schedule of Investments (Details) $ in Thousands	1 Months Ended
	Oct. 31, 2019USD ($)	Mar. 31, 2020USD ($)property	Dec. 31, 2019USD ($)
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		244
Investment balance		$ 296,692	$ 292,790
PR EXR Self Storage, LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		5
Equity Ownership %		25.00%
Excess Profit %		40.00%
Investment balance		$ 59,147	59,391
WICNN JV LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		10
Equity Ownership %		10.00%
Excess Profit %		25.00%
Investment balance		$ 36,445	36,552
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		$ 17,356	17,639
ESS-NYFL JV LP
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		11
Equity Ownership %		16.00%
Excess Profit %		24.00%
Investment balance		$ 12,611	13,320
GFN JV, LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		6
Equity Ownership %		10.00%
Excess Profit %		30.00%
Investment balance		$ 15,576	12,168
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		$ 9,073	9,133
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		$ 7,928	7,977
Storage Portfolio III JV LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		5
Equity Ownership %		10.00%
Excess Profit %		30.00%
Investment balance		$ 5,832	3,995
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		$ 2,914	3,046
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		$ (2,228)	(2,091)
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		$ (4,915)	(4,827)
Storage Portfolio I LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		24
Equity Ownership %		34.00%
Excess Profit %		49.00%
Investment balance		$ (38,570)	(38,345)
Other minority owned stores
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		19
Investment balance		$ 25,523	24,832
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%
SmartStop Self Storage REIT, Inc. Preferred Stock
Schedule of Equity Method Investments [Line Items]
Investment balance		$ 150,000	$ 150,000
Amount invested	$ 150
Investment commitment	$ 50
Investment commitment, period	12 months
Investment, preferred dividend rate	6.25%
Period after which preferred stock dividend is subject to increase	5 years
Period after which preferred stock is subject to increase	5 years

Variable Interests (Detail)

Variable Interests (Detail) $ in Thousands	1 Months Ended	3 Months Ended		12 Months Ended
	Jan. 31, 2019USD ($)	Mar. 31, 2020USD ($)joint_venture	Mar. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017subsidiary
Variable Interest Entity [Line Items]
Number of wholly-owned unconsolidated subsidiaries | subsidiary					3
Repayments of debt		$ 0	$ 30,928
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, 2020USD ($)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	$ 32,595
Number of derivative financial instruments | derivative	25
Combined notional amount	$ 2,396,948
Fair value - net liability position	116,411
Contingent cash settlement value	$ 116,411

Derivatives - Schedule of Balan

Derivatives - Schedule of Balance Sheet Classification and Fair Value of Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Other assets
Derivative [Line Items]
Derivative asset, fair value	$ 0	$ 6,214
Other liabilities
Derivative [Line Items]
Derivative liability, fair value	$ 113,986	$ 31,400

Derivatives - Gain (Loss) Recog

Derivatives - Gain (Loss) Recognized on Swap Agreements (Detail) - Swap Agreements - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Derivative [Line Items]
Gain (loss) recognized in OCI	$ (89,710)	$ (19,576)
Gain (loss) reclassified from OCI	$ (563)	$ 4,462

Exchangeable Senior Notes - Add

Exchangeable Senior Notes - Additional Information (Detail) - Exchangeable Senior Notes 3.125% due 2035 (the 2015 Notes)	1 Months Ended	3 Months Ended
	Sep. 30, 2015USD ($)	Mar. 31, 2020day
Debt Instrument [Line Items]
Principal amount of notes issued | $	$ 575,000,000
Debt stated interest rate		3.125%
Related debt issuance costs | $	$ 11,992,000
Underwriting fee percentage	2.00%
Amortization period		5 years
Conversion ratio		0.01093
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%
Notes exchange, threshold percentage		130.00%
Notes exchange, threshold trading days | day		20
Notes exchange, threshold consecutive trading days | day		30
Effective interest rate on the liability component		4.00%
Minimum
Debt Instrument [Line Items]
Number of days of written notice to holders of notes required for redemption		30 days
Maximum
Debt Instrument [Line Items]
Number of days of written notice to holders of notes required for redemption		60 days

Exchangeable Senior Notes - Sch

Exchangeable Senior Notes - Schedule of Information about Total Carrying Amounts of Equity Components, Principal Amounts of Liability Components, Unamortized Discounts and Net Carrying Amounts for Notes (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2015
Debt Instrument [Line Items]
Principal amount of liability component	$ 571,321	$ 569,513
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	(2,466)	(3,675)
Unamortized debt issuance costs	(1,213)	(1,812)
Net carrying amount of liability component	$ 571,321	$ 569,513

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, 2020	Mar. 31, 2019
Debt Disclosure [Abstract]
Contractual interest	$ 4,492	$ 4,492
Amortization of discount	1,209	1,162
Total interest expense recognized	$ 5,701	$ 5,654

Stockholders' Equity (Detail)

Stockholders' Equity (Detail)	May 15, 2019USD ($)sales_agent	Mar. 31, 2020USD ($)$ / sharesshares	Mar. 31, 2020USD ($)shares	Mar. 31, 2019USD ($)	Nov. 08, 2017USD ($)
Class of Stock [Line Items]
Number of sales agents | sales_agent	9
Period of share repurchase program			3 years
Authorized amount for repurchase					$ 400,000,000
Repurchase of common stock (in shares) | shares		653,597
Repurchase of common stock, average price (in dollars per share) | $ / shares		$ 79.85
Payments for repurchase of common stock		$ 52,204,000	$ 52,204,000	$ 0
Remaining authorized repurchase amount		347,796,000	$ 347,796,000
At the Market Equity Distribution Agreement
Class of Stock [Line Items]
Aggregate offering price of common shares	$ 500,000,000
Shares issued (in shares) | shares			0
Value of stock available for issuance under ATM		$ 298,621,000	$ 298,621,000

Noncontrolling Interest Repre_2

Noncontrolling Interest Represented by Preferred Operating Partnership Units (Details) - USD ($) $ / shares in Units, $ in Thousands	Apr. 25, 2019	Dec. 01, 2018	Apr. 18, 2017	Dec. 31, 2014	Oct. 31, 2014	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2007	Jun. 25, 2007
Noncontrolling Interest [Line Items]
Loans and notes to affiliates						$ 100,000
Note receivable interest rate						5.00%
Loan to affiliates				$ 20,230
Note receivable, reduction of noncontrolling interests						$ 18,524
Series A Units
Noncontrolling Interest [Line Items]
Fixed priority return on preferred OP units, amount					$ 101,700
Fixed priority return on preferred OP units, stated return rate			2.30%
Fixed priority return on preferred OP units, liquidation value					$ 101,700			$ 115,000
Preferred units outstanding (in shares)					875,480
Series B Units
Noncontrolling Interest [Line Items]
Preferred units outstanding (in shares)						1,676,087
Liquidation value (in dollars per share)						$ 25
Fixed liquidation value						$ 41,902
Annual rate of return percentage						6.00%
Series C Units
Noncontrolling Interest [Line Items]
Loans and notes to affiliates							$ 19,735
Liquidation value (in dollars per share)						$ 42.10
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						0.9145
Units converted (in shares)	296,020	407,996
Note receivable, reduction of noncontrolling interests							8,644
Series D Units
Noncontrolling Interest [Line Items]
Preferred units outstanding (in shares)						4,803,445
Liquidation value (in dollars per share)						$ 25
Fixed liquidation value						$ 120,086
Number of units issued (in shares)						1,120,924
Value of units issued						$ 28,023
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]
Loans and notes to affiliates									$ 100,000
Maximum number of preferred OP units converted prior to the maturity date of the loan (in shares)					114,500
Note receivable interest rate			2.10%
Noncontrolling Interest - Operating Partnership
Noncontrolling Interest [Line Items]
Issuance of units upon conversion (in shares)	270,709	373,113
Note receivable, reduction of noncontrolling interests						$ 18,524	$ 11,091

Noncontrolling Interest in Op_3

Noncontrolling Interest in Operating Partnership and Other Noncontrolling Interests - Additional Information (Details) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)joint_ventureproperty$ / sharesshares	Dec. 31, 2019USD ($)
Noncontrolling Interest [Line Items]
Note receivable, reduction of noncontrolling interests	$ 18,524
Note receivable interest rate	5.00%
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	$ 87.07
OP units outstanding (in shares) | shares	5,915,916
Consideration to be paid on redemption of common OP units	$ 515,099
Noncontrolling Interest - Operating Partnership
Noncontrolling Interest [Line Items]
Note receivable, reduction of noncontrolling interests	$ 18,524	$ 11,091
Common Stock
Noncontrolling Interest [Line Items]
OP units conversion ratio	1
Noncontrolling Interest - Operating Partnership
Noncontrolling Interest [Line Items]
Ownership interest held	93.80%
Ownership interest held by joint venture partner	6.20%
Other noncontrolling interests
Noncontrolling Interest [Line Items]
Number of consolidated joint ventures | joint_venture	2
Joint Venture 1 | Other noncontrolling interests
Noncontrolling Interest [Line Items]
Number of operating stores owned | property	4
Joint Venture 2 | Other noncontrolling interests
Noncontrolling Interest [Line Items]
Number of operating stores owned | property	1
Number of development stores owned | property	1
Minimum | Other noncontrolling interests
Noncontrolling Interest [Line Items]
Ownership interest held by joint venture partner	5.00%
Maximum | Other noncontrolling interests
Noncontrolling Interest [Line Items]
Ownership interest held by joint venture partner	20.00%
Series C Units
Noncontrolling Interest [Line Items]
Note receivable, reduction of noncontrolling interests		$ 8,644

Noncontrolling Interest in Op_4

Noncontrolling Interest in Operating Partnership and Other Noncontrolling Interests - Schedule of OP Unit Activity (Details) - shares	Mar. 31, 2020	Dec. 31, 2019
Noncontrolling Interest [Abstract]
OP Units redeemed for common stock (in units)	8,862	85,501

Segment Information - Additiona

Segment Information - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2020segment
Segment Reporting [Abstract]
Number of reportable segments	2

Segment Information - Schedule

Segment Information - Schedule of Financial Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Revenues:	$ 332,452	$ 311,546
Operating expenses:	175,261	163,069
Income from operations	157,191	148,477
Property management fees and other income	12,136	10,746
General and administrative expense	(23,011)	(22,678)
Depreciation and amortization expense	(55,275)	(54,659)
Interest expense	(44,358)	(47,360)
Non-cash interest expense related to amortization of discount on equity component of exchangeable senior notes	(1,209)	(1,162)
Interest income	1,674	1,388
Equity in earnings and dividend income from unconsolidated real estate entities	5,043	2,630
Income tax expense	(2,179)	(1,813)
Net income	116,162	102,160
Operating Segments
Segment Reporting Information [Line Items]
Revenues:	320,316	300,800
Operating expenses:	96,975	85,732
Income from operations	223,341	215,068
Operating Segments | Self-Storage Operations
Segment Reporting Information [Line Items]
Revenues:	286,703	271,003
Operating expenses:	90,297	78,765
Income from operations	196,406	192,238
Operating Segments | Tenant Reinsurance
Segment Reporting Information [Line Items]
Revenues:	33,613	29,797
Operating expenses:	6,678	6,967
Income from operations	$ 26,935	$ 22,830

Commitments and Contingencies (

Commitments and Contingencies (Detail) $ in Thousands	Mar. 31, 2020USD ($)store
Commitment To Acquire Stores
Other Commitments [Line Items]
Number of real estate properties to be acquired	3
Purchase price | $	$ 20,634
Commitment To Acquire Stores With Joint Venture Partners
Other Commitments [Line Items]
Number of real estate properties to be acquired	5
Purchase price | $	$ 25,770
Commitment To Acquire Retail Space With Joint Venture Partners, Scheduled To Close in 2020
Other Commitments [Line Items]
Number of stores scheduled to be closed	4