National Storage Affiliates Trust (NSA) 10-Q 6 Nov 20 2020 Q3 Quarterly report Financial data

COVER PAGE

COVER PAGE - shares	9 Months Ended
	Sep. 30, 2020	Nov. 05, 2020
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2020
Document Transition Report	false
Entity File Number	001-37351
Entity Registrant Name	National Storage Affiliates Trust
Entity Incorporation, State or Country Code	MD
Entity Tax Identification Number	46-5053858
Entity Address, Address Line One	8400 East Prentice Avenue, 9th Floor
Entity Address, City or Town	Greenwood Village
Entity Address, State or Province	CO
Entity Address, Postal Zip Code	80111
City Area Code	720
Local Phone Number	630-2600
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 (in shares)		69,197,623
Entity Central Index Key	0001618563
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Amendment Flag	false
Common Shares of Beneficial Interest, $0.01 par value per share
Entity Information [Line Items]
Title of 12(b) Security	Common Shares of Beneficial Interest, $0.01 par value per share
Trading Symbol	NSA
Security Exchange Name	NYSE
Series A Cumulative Redeemable Preferred Shares of Beneficial Interest, par value $0.01 per share
Entity Information [Line Items]
Title of 12(b) Security	Series A Cumulative Redeemable Preferred Shares of Beneficial Interest, par value $0.01 per share
Trading Symbol	NSA Pr A
Security Exchange Name	NYSE

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Real estate
Self storage properties	$ 3,381,418	$ 3,091,719
Less accumulated depreciation	(416,423)	(337,822)
Self storage properties, net	2,964,995	2,753,897
Cash and cash equivalents	16,779	20,558
Restricted cash	4,486	3,718
Debt issuance costs, net	2,698	3,264
Investment in unconsolidated real estate ventures	206,284	214,061
Other assets	62,320	65,441
Operating lease right-of-use assets	23,354	23,306
Total assets	3,280,916	3,084,245
Liabilities
Debt financing	1,741,703	1,534,047
Accounts payable and accrued liabilities	51,280	37,966
Interest rate swap liabilities	86,746	19,943
Operating lease liabilities	24,929	24,665
Deferred revenue	15,858	15,523
Total liabilities	1,920,516	1,632,144
Commitments and contingencies (Note 11)
Equity
Preferred shares of beneficial interest, par value $0.01 per share. 50,000,000 authorized, 8,732,719 and 8,727,119 issued and outstanding at September 30, 2020 and December 31, 2019, at liquidation preference	218,318	218,178
Common shares of beneficial interest, par value $0.01 per share. 250,000,000 authorized, 69,177,872 and 59,659,108 shares issued and outstanding at September 30, 2020 and December 31, 2019, respectively	692	597
Additional paid-in capital	993,164	905,763
Distributions in excess of earnings	(242,222)	(197,075)
Accumulated other comprehensive loss	(54,723)	(7,833)
Total shareholders' equity	915,229	919,630
Noncontrolling interests	445,171	532,471
Total equity	1,360,400	1,452,101
Total liabilities and equity	$ 3,280,916	$ 3,084,245

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - $ / shares	Sep. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Series A Preferred shares of beneficial interest, par value (in dollars per share)	$ 0.01	$ 0.01
Series A Preferred shares of beneficial interest, authorized (in shares)	50,000,000	50,000,000
Series A Preferred shares of beneficial interest, issued (in shares)	8,732,719	8,727,119
Series A Preferred shares of beneficial interest, outstanding (in shares)	8,732,719	8,727,119
Common shares of beneficial interest, par value (in dollars per share)	$ 0.01	$ 0.01
Common shares of beneficial interest, authorized (in shares)	250,000,000	250,000,000
Common shares of beneficial interest, issued (in shares)	69,177,872	59,659,108
Common shares of beneficial interest, outstanding (in shares)	69,177,872	59,659,108

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
REVENUE
Rental revenue	$ 99,690	$ 92,746	$ 290,394	$ 262,776
Total revenue	109,474	101,337	318,113	287,328
OPERATING EXPENSES
Property operating expenses	31,546	28,988	92,395	82,635
General and administrative expenses	10,818	11,271	32,241	32,464
Depreciation and amortization	28,933	27,598	87,347	77,776
Other	479	768	1,330	1,511
Total operating expenses	71,776	68,625	213,313	194,386
OTHER (EXPENSE) INCOME
Interest expense	(15,262)	(14,432)	(46,403)	(41,590)
Equity in earnings (losses) of unconsolidated real estate ventures	37	(1,214)	(251)	(4,962)
Acquisition costs	(596)	(321)	(1,681)	(783)
Non-operating expense	(120)	(8)	(629)	(275)
Gain on sale of self storage properties	0	0	0	2,814
Other expense	(15,941)	(15,975)	(48,964)	(44,796)
Income before income taxes	21,757	16,737	55,836	48,146
Income tax expense	(346)	(223)	(875)	(959)
Net income	21,411	16,514	54,961	47,187
Net income attributable to noncontrolling interests	(7,924)	(25,374)	(24,404)	(56,292)
Net income (loss) attributable to National Storage Affiliates Trust	13,487	(8,860)	30,557	(9,105)
Distributions to preferred shareholders	(3,275)	(3,272)	(9,822)	(9,117)
Net income (loss) attributable to common shareholders	$ 10,212	$ (12,132)	$ 20,735	$ (18,222)
Earnings (loss) per common share - basic and diluted
Earnings (loss) per share - basic and diluted (in dollars per share)	$ 0.15	$ (0.20)	$ 0.32	$ (0.32)
Weighted average shares outstanding - basic and diluted (in shares)	68,887	59,278	65,643	57,835
Dividends declared per common share (in dollars per share)	$ 0.34	$ 0.32	$ 1	$ 0.94
Other property-related revenue
REVENUE
Revenue	$ 3,883	$ 3,217	$ 10,672	$ 9,169
Management fees and other revenue
REVENUE
Revenue	$ 5,901	$ 5,374	$ 17,047	$ 15,383

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 21,411	$ 16,514	$ 54,961	$ 47,187
Other comprehensive (loss) income
Unrealized loss on derivative contracts	(562)	(17,433)	(77,354)	(44,547)
Reclassification of other comprehensive loss (income) to interest expense	4,973	(939)	9,519	(3,492)
Other comprehensive income (loss)	4,411	(18,372)	(67,835)	(48,039)
Comprehensive income (loss)	25,822	(1,858)	(12,874)	(852)
Comprehensive (income) loss attributable to noncontrolling interests	(9,323)	(18,821)	(146)	(38,981)
Comprehensive income (loss) attributable to National Storage Affiliates Trust	$ 16,499	$ (20,679)	$ (13,020)	$ (39,833)

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Common Shares of Beneficial Interest, $0.01 par value per share	Series A Cumulative Redeemable Preferred Shares of Beneficial Interest, par value $0.01 per share	Series A-1 preferred units, OP units, and subordinated performance units	OP units	Preferred Shares	Preferred SharesSeries A Cumulative Redeemable Preferred Shares of Beneficial Interest, par value $0.01 per share	Common Shares	Common SharesCommon Shares of Beneficial Interest, $0.01 par value per share	Additional Paid-in Capital	Additional Paid-in CapitalCommon Shares of Beneficial Interest, $0.01 par value per share	Additional Paid-in CapitalSeries A Cumulative Redeemable Preferred Shares of Beneficial Interest, par value $0.01 per share	Distributions In Excess Of Earnings	Accumulated Other Comprehensive (Loss) Income	Accumulated Other Comprehensive (Loss) IncomeCommon Shares of Beneficial Interest, $0.01 par value per share	Noncontrolling Interests	Noncontrolling InterestsCommon Shares of Beneficial Interest, $0.01 par value per share	Noncontrolling InterestsSeries A-1 preferred units, OP units, and subordinated performance units	Noncontrolling InterestsOP units
Balances (in shares) at Dec. 31, 2018						6,900,000
Balances (in shares) at Dec. 31, 2018								56,654,009
Balances at Dec. 31, 2018	$ 1,402,299					$ 172,500		$ 567		$ 844,276			$ (114,122)	$ 13,618		$ 485,460
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of equity units				$ 32,856														$ 32,856
Redemptions of equity units (in shares)								29,910
Redemptions of equity units	0							$ 0		250				7		(257)
Effect of changes in ownership for consolidated entities	0									(5,385)				(182)		5,567
Equity-based compensation expense	1,112									90						1,022
Issuance of LTIP units for acquisition expenses	5															5
Issuance of restricted common shares (in shares)								18,218
Issuance of restricted common shares	0
Vesting and forfeitures of restricted common shares, net (in shares)								(3,451)
Vesting and forfeitures of restricted common shares, net	(69)									(69)
Reduction in receivables from partners of the operating partnership	139															139
Preferred share dividends	(2,588)												(2,588)
Common share dividends	(17,010)												(17,010)
Distributions to noncontrolling interests	(17,181)															(17,181)
Other comprehensive income (loss)	(9,315)													(5,917)		(3,398)
Net income (loss)	12,940												7,411			5,529
Balances (in shares) at Mar. 31, 2019						6,900,000
Balances (in shares) at Mar. 31, 2019								56,698,686
Balances at Mar. 31, 2019	1,403,188					$ 172,500		$ 567		839,162			(126,309)	7,526		509,742
Balances (in shares) at Dec. 31, 2018						6,900,000
Balances (in shares) at Dec. 31, 2018								56,654,009
Balances at Dec. 31, 2018	1,402,299					$ 172,500		$ 567		844,276			(114,122)	13,618		485,460
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income (loss)	(48,039)
Net income (loss)	47,187
Balances (in shares) at Sep. 30, 2019						8,727,119
Balances (in shares) at Sep. 30, 2019								59,328,388
Balances at Sep. 30, 2019	1,457,206					$ 218,178		$ 593		901,530			(187,305)	(17,294)		541,504
Balances (in shares) at Mar. 31, 2019						6,900,000
Balances (in shares) at Mar. 31, 2019								56,698,686
Balances at Mar. 31, 2019	1,403,188					$ 172,500		$ 567		839,162			(126,309)	7,526		509,742
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of equity units				15,515	$ 8,540													15,515	$ 8,540
Redemptions of equity units (in shares)								224,618
Redemptions of equity units	0							$ 2		1,839				28		(1,869)
Issuance of shares, net of offering costs (in shares)							1,785,680	2,375,000
Issuance of shares, net of offering costs	70,637		$ 43,624				$ 44,642	$ 24		70,613		$ (1,018)
Effect of changes in ownership for consolidated entities	0									(9,179)				(28)		9,207
Equity-based compensation expense	1,108									82						1,026
Issuance of LTIP units for acquisition expenses	56															56
Vesting and forfeitures of restricted common shares, net (in shares)								(1,335)
Vesting and forfeitures of restricted common shares, net	0									0
Preferred share dividends	(3,257)												(3,257)
Common share dividends	(18,970)												(18,970)
Distributions to noncontrolling interests	(19,038)															(19,038)
Other comprehensive income (loss)	(20,352)													(12,992)		(7,360)
Net income (loss)	17,733												(7,656)			25,389
Balances (in shares) at Jun. 30, 2019						8,685,680
Balances (in shares) at Jun. 30, 2019								59,296,969
Balances at Jun. 30, 2019	1,498,784					$ 217,142		$ 593		901,499			(156,192)	(5,466)		541,208
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of equity units				950														950
Redemption of Series A-1 preferred units (in shares)						41,439
Redemption of Series A-1 preferred units	0					$ 1,036				20						(1,056)
Redemptions of equity units (in shares)								32,951
Redemptions of equity units	0							$ 0		277				(7)		(270)
Effect of changes in ownership for consolidated entities	0									(341)				(2)		343
Equity-based compensation expense	1,153									75						1,078
Issuance of LTIP units for acquisition expenses	118															118
Vesting and forfeitures of restricted common shares, net (in shares)								(1,532)
Vesting and forfeitures of restricted common shares, net	0									0
Reduction in receivables from partners of the operating partnership	137															137
Preferred share dividends	(3,272)												(3,272)
Common share dividends	(18,981)												(18,981)
Distributions to noncontrolling interests	(19,825)															(19,825)
Other comprehensive income (loss)	(18,372)													(11,819)		(6,553)
Net income (loss)	16,514												(8,860)			25,374
Balances (in shares) at Sep. 30, 2019						8,727,119
Balances (in shares) at Sep. 30, 2019								59,328,388
Balances at Sep. 30, 2019	$ 1,457,206					$ 218,178		$ 593		901,530			(187,305)	(17,294)		541,504
Balances (in shares) at Dec. 31, 2019	8,727,119					8,727,119
Balances (in shares) at Dec. 31, 2019	59,659,108							59,659,108
Balances at Dec. 31, 2019	$ 1,452,101					$ 218,178		$ 597		905,763			(197,075)	(7,833)		532,471
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of equity units				6,206														6,206
Redemption of Series A-1 preferred units (in shares)						5,600
Redemption of Series A-1 preferred units	0					$ 140										(140)
Redemptions of equity units (in shares)								118,961
Redemptions of equity units	0							$ 1		1,437				(62)		(1,376)
LTIP units	1,011															1,011
Issuance of shares, net of offering costs (in shares)									125,000
Issuance of shares, net of offering costs		$ 4,249							$ 1		$ 4,248
Merger and internalization of PRO, net of issuance costs (in shares)								8,105,192
Merger and internalization of PRO, net of issuance costs	9,595							$ 81		43,499				(402)		(33,583)
Effect of changes in ownership for consolidated entities	0									15,857				(2,265)		(13,592)
Equity-based compensation expense	774									76						698
Issuance of LTIP units for acquisition expenses	40															40
Issuance of restricted common shares (in shares)								21,861
Issuance of restricted common shares	0
Vesting and forfeitures of restricted common shares, net (in shares)								(2,910)
Vesting and forfeitures of restricted common shares, net	(94)									(94)
Preferred share dividends	(3,273)												(3,273)
Common share dividends	(19,747)												(19,747)
Distributions to noncontrolling interests	(19,813)															(19,813)
Other comprehensive income (loss)	(65,757)													(42,293)		(23,464)
Net income (loss)	15,763												6,648			9,115
Balances (in shares) at Mar. 31, 2020						8,732,719
Balances (in shares) at Mar. 31, 2020								68,027,212
Balances at Mar. 31, 2020	$ 1,381,055					$ 218,318		$ 680		970,786			(213,447)	(52,855)		457,573
Balances (in shares) at Dec. 31, 2019	8,727,119					8,727,119
Balances (in shares) at Dec. 31, 2019	59,659,108							59,659,108
Balances at Dec. 31, 2019	$ 1,452,101					$ 218,178		$ 597		905,763			(197,075)	(7,833)		532,471
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income (loss)	(67,835)
Net income (loss)	$ 54,961
Balances (in shares) at Sep. 30, 2020	8,732,719					8,732,719
Balances (in shares) at Sep. 30, 2020	69,177,872							69,177,872
Balances at Sep. 30, 2020	$ 1,360,400					$ 218,318		$ 692		993,164			(242,222)	(54,723)		445,171
Balances (in shares) at Mar. 31, 2020						8,732,719
Balances (in shares) at Mar. 31, 2020								68,027,212
Balances at Mar. 31, 2020	1,381,055					$ 218,318		$ 680		970,786			(213,447)	(52,855)		457,573
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of equity units				5,842														5,842
Redemptions of equity units (in shares)								292,291
Redemptions of equity units	0							$ 3		3,438				(238)		(3,203)
Issuance of shares, net of offering costs (in shares)									387,000
Issuance of shares, net of offering costs		11,916							$ 4		11,912
Effect of changes in ownership for consolidated entities	0									(1,286)				(73)		1,359
Equity-based compensation expense	1,151									100						1,051
Vesting and forfeitures of restricted common shares, net (in shares)								(2,770)
Vesting and forfeitures of restricted common shares, net	0									0
Reduction in receivables from partners of the operating partnership	225															225
Preferred share dividends	(3,274)												(3,274)
Common share dividends	(22,625)												(22,625)
Distributions to noncontrolling interests	(16,843)															(16,843)
Other comprehensive income (loss)	(6,489)													(4,296)		(2,193)
Net income (loss)	17,787												10,422			7,365
Balances (in shares) at Jun. 30, 2020						8,732,719
Balances (in shares) at Jun. 30, 2020								68,703,733
Balances at Jun. 30, 2020	1,368,745					$ 218,318		$ 687		984,950			(228,924)	(57,462)		451,176
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of equity units				$ 3,427														$ 3,427
Redemptions of equity units (in shares)									293,083
Redemptions of equity units		0							$ 3		3,417				$ (249)		$ (3,171)
Issuance of shares, net of offering costs (in shares)									181,915
Issuance of shares, net of offering costs		$ 5,868							$ 2		$ 5,866
Effect of changes in ownership for consolidated entities	0									(1,170)				(24)		1,194
Equity-based compensation expense	1,183									101						1,082
Vesting and forfeitures of restricted common shares, net (in shares)								(859)
Vesting and forfeitures of restricted common shares, net	0									0
Reduction in receivables from partners of the operating partnership	37															37
Preferred share dividends	(3,275)												(3,275)
Common share dividends	(23,510)												(23,510)
Distributions to noncontrolling interests	(17,897)															(17,897)
Other comprehensive income (loss)	4,411													3,012		1,399
Net income (loss)	$ 21,411												13,487			7,924
Balances (in shares) at Sep. 30, 2020	8,732,719					8,732,719
Balances (in shares) at Sep. 30, 2020	69,177,872							69,177,872
Balances at Sep. 30, 2020	$ 1,360,400					$ 218,318		$ 692		$ 993,164			$ (242,222)	$ (54,723)		$ 445,171

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
OPERATING ACTIVITIES
Net income	$ 54,961	$ 47,187
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	87,347	77,776
Amortization of debt issuance costs	2,291	2,150
Amortization of debt discount and premium, net	(894)	(1,067)
Gain on sale of self storage properties	0	(2,814)
Mark-to-market changes in value on equity securities	142	0
Equity-based compensation expense	3,108	3,373
Equity in losses of unconsolidated real estate ventures	251	4,962
Distributions from unconsolidated real estate ventures	10,628	10,700
Change in assets and liabilities, net of effects of self storage property acquisitions:
Other assets	(1,555)	(1,273)
Accounts payable and accrued liabilities	12,008	10,734
Deferred revenue	(642)	(1,647)
Net Cash Provided by Operating Activities	167,645	150,081
INVESTING ACTIVITIES
Acquisition of self storage properties	(259,003)	(342,175)
Capital expenditures	(13,018)	(15,926)
Investments in and advances to unconsolidated real estate ventures	(3,125)	0
Distributions from unconsolidated real estate ventures	0	1,017
Deposits and advances for self storage property and other acquisitions	(550)	0
Proceeds from sale of equity securities	7,560	0
Expenditures for corporate furniture, equipment and other	(362)	(7,022)
Acquisition of interest in reinsurance company and related cash flows	0	(6,600)
Proceeds from sale of self storage properties	0	6,335
Net Cash Used In Investing Activities	(268,498)	(364,371)
FINANCING ACTIVITIES
Proceeds from issuance of common shares	22,033	70,637
Proceeds from issuance of preferred shares	0	43,624
Borrowings under debt financings	415,500	822,000
Receipts for OP unit subscriptions	661	629
Principal payments under debt financings	(208,607)	(560,316)
Payment of dividends to common shareholders	(65,882)	(54,961)
Distributions to preferred shareholders	(9,822)	(9,117)
Distributions to noncontrolling interests	(54,291)	(55,768)
Debt issuance costs	(865)	(8,416)
Equity offering costs	(885)	(179)
Net Cash Provided By Financing Activities	97,842	248,133
(Decrease) Increase in Cash, Cash Equivalents and Restricted Cash	(3,011)	33,843
CASH, CASH EQUIVALENTS AND RESTRICTED CASH
Beginning of period	24,276	16,363
End of period	21,265	50,206
Supplemental Cash Flow and Noncash Information
Cash paid for interest	46,705	39,848
Operating lease right-of-use assets on balance sheet due to implementation of leases standard	23,354	23,507
Operating lease liabilities on balance sheet due to implementation of leases standard	24,929	24,777
Redemptions and conversions of partnership interests	33,583	0
Issuance of common shares for management platform	$ 10,301	$ 0

ORGANIZATION AND NATURE OF OPER

ORGANIZATION AND NATURE OF OPERATIONS	9 Months Ended
	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
ORGANIZATION AND NATURE OF OPERATIONS	ORGANIZATION AND NATURE OF OPERATIONS National Storage Affiliates Trust was organized in the state of Maryland on May 16, 2013 and is a fully integrated, self-administered and self-managed real estate investment trust focused on the self storage sector. As used herein, "NSA," the "Company," "we," "our," and "us" refers to National Storage Affiliates Trust and its consolidated subsidiaries, except where the context indicates otherwise. The Company has elected and believes that it has qualified to be taxed as a real estate investment trust for U.S. federal income tax purposes ("REIT") commencing with its taxable year ended December 31, 2015. Through its controlling interest as the sole general partner of NSA OP, LP (its "operating partnership"), a Delaware limited partnership formed on February 13, 2013, the Company is focused on the ownership, operation, and acquisition of self storage properties located within the top 100 metropolitan statistical areas throughout the United States. Pursuant to the Agreement of Limited Partnership (as amended, the "LP Agreement") of its operating partnership, the Company's operating partnership is authorized to issue preferred units, Class A Units ("OP units"), different series of Class B Units ("subordinated performance units"), and Long-Term Incentive Plan Units ("LTIP units"). The Company also owns certain of its self storage properties through other consolidated limited partnership subsidiaries of its operating partnership, which the Company refers to as "DownREIT partnerships." The DownREIT partnerships issue equity ownership interests that are intended to be economically equivalent to the Company's OP units ("DownREIT OP units") and subordinated performance units ("DownREIT subordinated performance units"). The Company owned 611 consolidated self storage properties in 29 states and Puerto Rico with approximately 36.8 million rentable square feet in approximately 293,000 storage units as of September 30, 2020. These properties are managed with local operational focus and expertise by the Company and its participating regional operators ("PROs"). These PROs are Kevin Howard Real Estate Inc., d/b/a Northwest Self Storage and its controlled affiliates ("Northwest"), Optivest Properties LLC and its controlled affiliates ("Optivest"), Guardian Storage Centers LLC and its controlled affiliates ("Guardian"), Move It Self Storage and its controlled affiliates ("Move It"), Arizona Mini Storage Management Company d/b/a Storage Solutions and its controlled affiliates ("Storage Solutions"), Hide-Away Storage Services, Inc. and its controlled affiliates ("Hide-Away"), an affiliate of Shader Brothers Corporation d/b/a Personal Mini Storage ("Personal Mini"), Southern Storage Management Systems, Inc. d/b/a Southern Self Storage ("Southern") and affiliates of Investment Real Estate Management, LLC d/b/a Moove In Self Storage of York, Pennsylvania ("Moove In"). On March 31, 2020, the Company closed on the mergers of its largest PRO, SecurCare Self Storage, Inc. and its controlled affiliates ("SecurCare"), and DLAN Corporation ("DLAN") with and into wholly-owned subsidiaries of the Company. As a result of the mergers, SecurCare's property management platform and related intellectual property were internalized by the Company, and the Company no longer pays any supervisory and administrative fees or reimbursements to SecurCare. In addition, distributions on the series of subordinated performance units related to SecurCare's managed portfolio were discontinued. As part of the internalization, most of SecurCare's employees and other key persons were offered and provided employment by the Company and continue managing SecurCare's portfolio of properties under the brand SecurCare as members of the Company's existing property management platform. As of September 30, 2020, the Company also managed through its property management platform an additional portfolio of 177 properties owned by the Company's unconsolidated real estate ventures. These properties contain approximately 12.7 million rentable square feet, configured in approximately 103,000 storage units and located across 21 states. The Company owns a 25% equity interest in each of its unconsolidated real estate ventures. As of September 30, 2020, in total, the Company operated and held ownership interests in 788 self storage properties located across 35 states and Puerto Rico with approximately 49.5 million rentable square feet in approximately 396,000 storage units.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The accompanying condensed consolidated financial statements are presented on the accrual basis of accounting in accordance with U.S. generally accepted accounting principles ("GAAP") and have been prepared by the Company pursuant to the rules and regulations of the Securities and Exchange Commission (the "SEC") regarding interim financial reporting. Accordingly, certain information and footnote disclosures required by GAAP for complete financial statements have been condensed or omitted in accordance with such rules and regulations. In the opinion of management, all adjustments (consisting of normal recurring adjustments) considered necessary for a fair presentation of the condensed consolidated financial statements have been included. The Company's results of operations for the quarterly and year to date periods are not necessarily indicative of the results to be expected for the full year or any other future period. Principles of Consolidation The Company's financial statements include the accounts of its operating partnership and its controlled subsidiaries. All significant intercompany balances and transactions have been eliminated in the consolidation of entities. When the Company obtains an economic interest in an entity, the Company evaluates the entity to determine if the entity is deemed a variable interest entity ("VIE"), and if the Company is deemed to be the primary beneficiary, in accordance with authoritative guidance issued on the consolidation of VIEs. When an entity is not deemed to be a VIE, the Company considers the provisions of additional guidance to determine whether the general partner controls a limited partnership or similar entity when the limited partners have certain rights. The Company consolidates all entities that are VIEs and of which the Company is deemed to be the primary beneficiary. The Company has determined that its operating partnership is a VIE. The sole significant asset of National Storage Affiliates Trust is its investment in its operating partnership, and consequently, substantially all of the Company’s assets and liabilities represent those assets and liabilities of its operating partnership. As of September 30, 2020 and December 31, 2019, the Company's operating partnership was the primary beneficiary of, and therefore consolidated, 21 DownREIT partnerships that are considered VIEs, which owned 34 self storage properties. The net book value of the real estate owned by these VIEs was $227.2 million and $233.1 million as of September 30, 2020 and December 31, 2019, respectively. For certain DownREIT partnerships which are subject to fixed rate mortgages payable, the carrying value of such fixed rate mortgages payable held by these VIEs was $100.7 million and $136.4 million as of September 30, 2020 and December 31, 2019, respectively. The creditors of the consolidated VIEs do not have recourse to the Company's general credit. Reclassifications Certain amounts in the condensed consolidated financial statements and related notes have been reclassified to conform to the current year presentation. Such reclassifications do not impact the Company's previously reported financial position or net income (loss). Revenue Recognition Rental revenue Rental revenue consists of space rentals and related fees. Management has determined that all of the Company's leases are operating leases. Substantially all leases may be terminated on a month-to-month basis and rental income is recognized ratably over the lease term using the straight-line method. Rents received in advance are deferred and recognized on a straight-line basis over the related lease term associated with the prepayment. Promotional discounts and other incentives are recognized as a reduction to rental income over the applicable lease term. Other property-related revenue Other property-related revenue primarily consists of ancillary revenues such as tenant insurance and/or tenant warranty protection-related access fees, sales of storage supplies and truck rentals which are recognized in the period earned. The Company and certain of the Company’s PROs have tenant insurance- and/or tenant warranty protection plan-related arrangements with insurance companies and the Company’s tenants. During the three months ended September 30, 2020 and 2019, the Company recognized $2.9 million and $2.4 million, respectively, of tenant insurance and tenant warranty protection plan revenues and during the nine months ended September 30, 2020 and 2019, the Company recognized $8.2 million and $6.7 million, respectively, of tenant insurance and tenant warranty protection plan revenues. The Company sells boxes, packing supplies, locks, other retail merchandise and rents moving trucks at its properties. During the three months ended September 30, 2020 and 2019, the Company recognized retail sales of $0.6 million and $0.4 million, respectively, and during the nine months ended September 30, 2020 and 2019, the Company recognized retail sales of $1.4 million and $1.3 million, respectively. Management fees and other revenue Management fees and other revenue consist of property management fees, platform fees, call center fees, acquisition fees, and a portion of tenant warranty protection or tenant insurance proceeds that the Company earns for managing and operating its unconsolidated real estate ventures. With respect to both the 2018 Joint Venture and the 2016 Joint Venture (as each is defined in Note 5), the Company provides supervisory and administrative property management services, centralized call center services, and technology platform and revenue management services to the properties in the unconsolidated real estate ventures. The property management fees are equal to 6% of monthly gross revenues and net sales revenues from the assets of the unconsolidated real estate ventures, and the platform fees are equal to $1,250 per month per unconsolidated real estate venture property. With respect to the 2016 Joint Venture only, the call center fees are equal to 1% of each of monthly gross revenues and net sales revenues from the 2016 Joint Venture properties. During the three months ended September 30, 2020 and 2019, the Company recognized property management fees, call center fees and platform fees of $3.4 million and $3.3 million, respectively, and during the nine months ended September 30, 2020 and 2019, the Company recognized property management fees, call center fees and platform fees of $9.8 million and $9.7 million, respectively. For acquisition fees, the Company provides sourcing, underwriting and administration services to the unconsolidated real estate ventures. The 2016 Joint Venture paid the Company a $4.1 million acquisition fee equal to 0.65% of the gross capitalization (including debt and equity) of the original 66-property 2016 Joint Venture portfolio (the "Initial 2016 JV Portfolio") in 2016, at the time of the Initial 2016 JV Portfolio acquisition. The 2018 Joint Venture paid the Company a $4.0 million acquisition fee related to the initial acquisition of properties by the 2018 Joint Venture (the "Initial 2018 JV Portfolio") in 2018, at the time of the Initial 2018 JV Portfolio acquisition. These fees are refundable to the unconsolidated real estate ventures, on a prorated basis, if the Company is removed as the managing member during the initial four four The Company also earns acquisition fees for properties acquired by the unconsolidated real estate ventures subsequent to the Initial 2016 JV Portfolio and the Initial 2018 JV Portfolio. These fees are based on a percentage of the gross capitalization of the acquired assets determined by the members of the 2016 Joint Venture and the 2018 Joint Venture, and are generally earned when the unconsolidated real estate ventures obtain title and control of an acquired property. During the three months ended September 30, 2020 and 2019, the Company recognized acquisition fees of $0.5 million and $0.4 million, respectively, and during the nine months ended September 30, 2020 and 2019, the Company recognized acquisition fees of $1.4 million and $1.4 million, respectively. An affiliate of the Company facilitates tenant warranty protection or tenant insurance programs for tenants of the properties in the unconsolidated real estate ventures in exchange for 50% of all proceeds from such programs at each unconsolidated real estate venture property. During the three months ended September 30, 2020 and 2019, the Company recognized $2.0 million and $1.2 million, respectively, of revenue related to these activities and during the nine months ended September 30, 2020 and 2019, the Company recognized $5.5 million and $3.6 million, respectively, of revenue related to these activities. Gain on sale of self storage properties The Company recognizes gains from disposition of facilities only upon closing in accordance with the guidance on sales of nonfinancial assets. Profit on real estate sold is recognized upon closing when all, or substantially all, of the promised consideration has been received and is nonrefundable and the Company has transferred control of the facilities to the purchaser. Investments in Unconsolidated Real Estate Ventures The Company’s investments in its unconsolidated real estate ventures are recorded under the equity method of accounting in the accompanying condensed consolidated financial statements. Under the equity method, the Company’s investments in unconsolidated real estate ventures are stated at cost and adjusted for the Company’s share of net earnings or losses and reduced by distributions. Equity in earnings (losses) is recognized based on the Company’s ownership interest in the earnings (losses) of the unconsolidated real estate ventures. The Company follows the "nature of the distribution approach" for classification of distributions from its unconsolidated real estate ventures in its condensed consolidated statements of cash flows. Under this approach, distributions are reported on the basis of the nature of the activity or activities that generated the distributions as either a return on investment, which are classified as operating cash flows, or a return of investment (e.g., proceeds from the unconsolidated real estate ventures' sale of assets) which are reported as investing cash flows. Noncontrolling Interests All of the limited partner equity interests ("OP equity") in the operating partnership not held by the Company are reflected as noncontrolling interests. Noncontrolling interests also include ownership interests in DownREIT partnerships held by entities other than the operating partnership or its subsidiaries. In the condensed consolidated statements of operations, the Company allocates net income (loss) attributable to noncontrolling interests to arrive at net income (loss) attributable to National Storage Affiliates Trust. For transactions that result in changes to the Company's ownership interest in its operating partnership, the carrying amount of noncontrolling interests is adjusted to reflect such changes. The difference between the fair value of the consideration received or paid and the amount by which the noncontrolling interest is adjusted is reflected as an adjustment to additional paid-in capital on the condensed consolidated balance sheets. Allocation of Net Income (Loss) The distribution rights and priorities set forth in the operating partnership's LP Agreement differ from what is reflected by the underlying percentage ownership interests of the unitholders. Accordingly, the Company allocates GAAP income (loss) utilizing the hypothetical liquidation at book value ("HLBV") method, in which the Company allocates income or loss based on the change in each unitholders’ claim on the net assets of its operating partnership at period end after adjusting for any distributions or contributions made during such period. The HLBV method is commonly applied to equity investments where cash distribution percentages vary at different points in time and are not directly linked to an equity holder’s ownership percentage. The HLBV method is a balance sheet-focused approach to income (loss) allocation. A calculation is prepared at each balance sheet date to determine the amount that unitholders would receive if the operating partnership were to liquidate all of its assets (at GAAP net book value) and distribute the resulting proceeds to its creditors and unitholders based on the contractually defined liquidation priorities. The difference between the calculated liquidation distribution amounts at the beginning and the end of the reporting period, after adjusting for capital contributions and distributions, is used to derive each unitholder's share of the income (loss) for the period. Due to the stated liquidation priorities and because the HLBV method incorporates non-cash items such as depreciation expense, in any given period, income or loss may be allocated disproportionately to unitholders as compared to their respective ownership percentage in the operating partnership, and net income (loss) attributable to National Storage Affiliates Trust could be more or less net income than actual cash distributions received and more or less income or loss than what may be received in the event of an actual liquidation. Additionally, the HLBV method could result in net income (or net loss) attributable to National Storage Affiliates Trust during a period when the Company reports consolidated net loss (or net income), or net income (or net loss) attributable to National Storage Affiliates Trust in excess of the Company's consolidated net income (or net loss). The computations of basic and diluted earnings (loss) per share may be materially affected by these disproportionate income (loss) allocations, resulting in volatile fluctuations of basic and diluted earnings (loss) per share. Other Comprehensive Income (Loss) The Company has cash flow hedge derivative instruments that are measured at fair value with unrealized gains or losses recognized in other comprehensive income (loss) with a corresponding adjustment to accumulated other comprehensive income (loss) within equity, as discussed further in Note 12. Under the HLBV method of allocating income (loss) discussed above, a calculation is prepared at each balance sheet date by applying the HLBV method including, and excluding, the assets and liabilities resulting from the Company's cash flow hedge derivative instruments to determine comprehensive income (loss) attributable to National Storage Affiliates Trust. As a result of the distribution rights and priorities set forth in the operating partnership's LP Agreement, in any given period, other comprehensive income (loss) may be allocated disproportionately to unitholders as compared to their respective ownership percentage in the operating partnership and as compared to their respective allocation of net income (loss). Restricted Cash The Company's restricted cash consists of escrowed funds deposited with financial institutions for real estate taxes, insurance and other reserves for capital improvements in accordance with the Company's loan agreements. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Recent Accounting Pronouncements In March 2020, the Financial Accounting Standards Board issued ASU 2020-04, Reference Rate Reform (Topic 848). ASU 2020-04 contains practical expedients for reference rate reform related activities that impact debt, leases, derivatives and other contracts. The guidance in ASU 2020-04 is optional and may be elected over time as reference rate reform activities occur. During the nine months ended September 30, 2020, the Company elected to apply the hedge accounting expedients related to probability and the assessments of effectiveness for future LIBOR-indexed cash flows to assume that the index upon which future hedged transactions will be based matches the index on the corresponding derivatives. Application of these expedients preserves the presentation of derivatives consistent with past presentation. The Company continues to evaluate the impact of the guidance and may apply other elections as applicable as additional changes in the market occur. See Note 12 for additional detail about the Company's derivatives.

SHAREHOLDERS' EQUITY AND NONCON

SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS	SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS Shareholders' Equity Forward Equity Offering On September 22, 2020, the Company entered into an underwriting agreement, as well as certain forward sale agreements, with a syndicate of banks acting as underwriters, forward sellers, and/or forward purchasers in connection with an underwritten public offering of 4,500,000 common shares at a public offering price of $33.15 per share. The underwriters were granted a 30-day option to purchase up to an additional 675,000 common shares at the same price, which they partially exercised for an additional 400,000 common shares on October 6, 2020. Therefore, the forward sellers or their affiliates, at the Company's request, borrowed from third parties and sold to the underwriters an aggregate of 4,900,000 common shares, which the underwriters sold at an offering price of $33.15 per share, for proceeds of approximately $162.4 million. As a result of this forward construct, the Company did not receive any proceeds from the sale of such shares at closing. The Company expects to settle the forward sale agreements within six months of the offering date via the issuance and physical delivery of the Company's common shares in exchange for cash proceeds, although the Company may elect cash settlement or net share settlement for all or a portion of its obligations under the forward sale agreements, subject to certain conditions. The forward sale price that the Company will receive upon physical settlement of the agreements is subject to subsequent adjustments from time to time as provided in the forward sale agreements. As of September 30, 2020, none of these shares had been settled. The initial forward sale price is $32.832 per share and assuming full physical settlement at the initial forward sale price, the Company would receive proceeds of approximately $160 million. The Company has determined that the forward sale agreements agreements are not considered to be derivative instruments under the guidance within ASC 815. Internalization and Acquisition of PRO As discussed in Note 1 and further below, on March 31, 2020, the Company closed on the previously announced mergers of SecurCare and DLAN with and into wholly-owned subsidiaries of the Company. In connection with the mergers, the Company issued 8,105,192 common shares to the owners of SecurCare and DLAN, which represented a 1% discount to an aggregate of 8,187,052 OP units that each of SecurCare and DLAN owned or was entitled to receive immediately prior to the mergers (after rounding up to the next whole number of common shares). Of the total number of common shares issued to the owners of SecurCare, 4,063,571 common shares were issued to Arlen Nordhagen, the Company's executive chairman and former chief executive officer, who owned approximately 53% of SecurCare's outstanding shares, and 1,858,737 common shares were issued to David Cramer, the Company's chief operating officer, who owned approximately 24% of SecurCare's outstanding shares. In connection with the mergers and the issuance of the Company's common shares to Mr. Nordhagen and Mr. Cramer, the Company formed a special committee of independent and disinterested trustees (the "Special Committee") to evaluate the merits and terms of the proposed transaction. In analyzing the proposed transaction, the Special Committee engaged an independent third party financial advisor to assist the Special Committee in analyzing and assessing the transaction, and to opine on the fairness to the Company of the consideration to be paid by the Company in the mergers. The Special Committee approved and recommended that the Company's board of trustees approve the proposed transaction. The transaction was approved unanimously by the disinterested trustees of the Company's board of trustees on February 19, 2020. At the Market ("ATM") Program On February 27, 2019, the Company entered into a sales agreement with certain sales agents, pursuant to which the Company may sell from time to time up to $250.0 million of the Company's common shares of beneficial interest, $0.01 par value per share ("common shares") and 6.000% Series A cumulative redeemable preferred shares of beneficial interest ("Series A preferred shares") in sales deemed to be "at the market" offerings. The sales agreement contemplates that, in addition to the issuance and sale by the Company of offered shares to or through the sale agents, the Company may enter into separate forward sale agreements with any forward purchaser. Forward sale agreements, if any, will include only the Company's common shares and will not include any Series A preferred shares. If the Company enters into a forward sale agreement with any forward purchaser, such forward purchaser will attempt to borrow from third parties and sell, through the related agent, acting as sales agent for such forward purchaser (each, a "forward seller"), offered shares, in an amount equal to the offered shares subject to such forward sale agreement, to hedge such forward purchaser’s exposure under such forward sale agreement. The Company may offer the common shares and Series A preferred shares through the agents, as the Company's sales agents, or, as applicable, as forward seller, or directly to the agents or forward sellers, acting as principals, by means of, among others, ordinary brokers’ transactions on the NYSE or otherwise at market prices prevailing at the time of sale or at negotiated prices. During the nine months ended September 30, 2020, the Company sold 693,915 of its common shares through the ATM program at an average offering price of $32.92 per share, resulting in net proceeds to the Company of approximately $22.0 million, after deducting compensation payable by the Company to such agents and offering expenses. Noncontrolling Interests All of the OP equity in the Company's operating partnership not held by the Company are reflected as noncontrolling interests. Noncontrolling interests also include ownership interests in DownREIT partnerships held by entities other than the Company's operating partnership. NSA is the general partner of its operating partnership and is authorized to cause its operating partnership to issue additional partner interests, including OP units and subordinated performance units, at such prices and on such other terms as it determines in its sole discretion. As of September 30, 2020 and December 31, 2019, units reflecting noncontrolling interests consisted of the following: September 30, 2020 December 31, 2019 Series A-1 preferred units 637,382 642,982 OP units 29,443,460 30,188,305 Subordinated performance units 8,770,744 11,014,195 LTIP units 765,840 743,566 DownREIT units DownREIT OP units 1,924,918 1,848,261 DownREIT subordinated performance units 4,337,111 4,371,622 Total 45,879,455 48,808,931 Series A-1 Preferred Units The 6.000% Series A-1 Cumulative Redeemable Preferred Units ("Series A-1 preferred units") rank senior to OP units and subordinated performance units in the Company's operating partnership with respect to distributions and liquidation. The Series A-1 preferred units have a stated value of $25.00 per unit and receive distributions at an annual rate of 6.000%. These distributions are cumulative. The Series A-1 preferred units are redeemable at the option of the holder after the first anniversary of the date of issuance, which redemption obligations may be satisfied at the Company’s option in cash in an amount equal to the market value of an equivalent number of the Series A preferred shares or the issuance of Series A preferred shares on a one-for-one basis, subject to adjustments. The Series A preferred shares are redeemable by the Company for a cash redemption price of $25.00 per share, plus accrued but unpaid dividends. The decrease in Series A-1 preferred units outstanding from December 31, 2019 to September 30, 2020 was due to the redemption of 5,600 Series A-1 preferred units for Series A preferred shares. OP Units and DownREIT OP units OP units in the Company's operating partnership are redeemable for cash or, at the Company's option, exchangeable for the Company's common shares on a one-for-one basis, and DownREIT OP units are redeemable for cash or, at the Company's option, exchangeable for OP units in its operating partnership on a one-for-one basis, subject to certain adjustments in each case. The holders of OP units are generally not entitled to elect redemption until one year after the issuance of the OP units. The holders of DownREIT OP units are generally not entitled to elect redemption until five years after the date of the contributor's initial contribution. The decrease in OP units outstanding from December 31, 2019 to September 30, 2020 was due to the redemption of 704,335 OP units for common shares and the exchange of 368,500 DownREIT OP units in redemption of an equivalent number of outstanding OP units, which were subsequently retired by the operating partnership, offset by the following: 445,701 OP units issued upon the conversion of 332,738 subordinated performance units (as discussed further below), 378,239 OP units issued in connection with the acquisition of self storage properties and 214,512 LTIP units which were converted into an equivalent number of OP units. In addition, in connection with the completion of the SecurCare and DLAN mergers, the Company's operating partnership retired 710,462 OP Units. The increase in DownREIT OP units outstanding from December 31, 2019 to September 30, 2020 was due to the exchange of 368,500 DownREIT OP units held by the operating partnership in redemption of an equivalent number of outstanding OP Units, which were subsequently retired by the operating partnership, and the issuance of 115,888 DownREIT OP units related to the conversion of 34,511 DownREIT subordinated performance units (as discussed further below) partially offset by the contribution of 407,731 DownREIT OP units (which were previously included in the above table because they were not held by the Company) to the operating partnership in connection with the SecurCare and DLAN mergers. Subordinated Performance Units and DownREIT Subordinated Performance Units Subordinated performance units may also, under certain circumstances, be convertible into OP units which are exchangeable for common shares as described above, and DownREIT subordinated performance units may, under certain circumstances, be exchangeable for subordinated performance units on a one-for-one basis. Subordinated performance units are only convertible into OP units after a two Following such lock-out period, a holder of subordinated performance units in the Company's operating partnership may elect a voluntary conversion one time each year on or prior to December 1st to convert a pre-determined portion of such subordinated performance units into OP units in the Company's operating partnership, with such conversion effective January 1st of the following year, with each subordinated performance unit being converted into the number of OP units determined by dividing the average cash available for distribution, or CAD, per unit on the series of specific subordinated performance units over the one application of the provisions of the LP Agreement applicable to the distributions of operating cash flow and capital transactions proceeds. The decrease in subordinated performance units outstanding from December 31, 2019 to September 30, 2020 was due to the retirement of 2,001,441 subordinated performance units in connection with the SecurCare merger and the voluntary conversion of 332,738 subordinated performance units into 445,701 OP units, partially offset by the issuance of 90,728 subordinated performance units for co-investment by the Company's PROs in connection with the acquisition of self storage properties. The decrease in DownREIT subordinated performance units outstanding from December 31, 2019 to September 30, 2020 was due to the conversion of 34,511 DownREIT subordinated performance units into 115,888 DownREIT OP units. LTIP Units LTIP units are a special class of partnership interest in the Company's operating partnership that allow the holder to participate in the ordinary and liquidating distributions received by holders of the OP units (subject to the achievement of specified levels of profitability by the Company's operating partnership or the achievement of certain events). LTIP units may also, under certain circumstances, be convertible into OP units on a one-for-one basis, which are then exchangeable for common shares as described above.

SELF STORAGE PROPERTIES

SELF STORAGE PROPERTIES	9 Months Ended
	Sep. 30, 2020
Real Estate [Abstract]
SELF STORAGE PROPERTIES	SELF STORAGE PROPERTIES Self storage properties are summarized as follows (dollars in thousands): September 30, 2020 December 31, 2019 Land $ 690,581 $ 649,938 Buildings and improvements 2,683,288 2,435,171 Furniture and equipment 7,549 6,610 Total self storage properties 3,381,418 3,091,719 Less accumulated depreciation (416,423) (337,822) Self storage properties, net $ 2,964,995 $ 2,753,897 Depreciation expense related to self storage properties amounted to $26.6 million and $23.8 million during the three months ended September 30, 2020 and 2019, respectively, and $78.6 million and $68.0 million during the nine months ended September 30, 2020 and 2019, respectively.

INVESTMENT IN UNCONSOLIDATED RE

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES	9 Months Ended
	Sep. 30, 2020
Equity Method Investments and Joint Ventures [Abstract]
INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES	INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES 2018 Joint Venture As of September 30, 2020, the Company's unconsolidated real estate venture, formed in September 2018 with an affiliate of Heitman America Real Estate REIT LLC (the "2018 Joint Venture"), owned and operated a portfolio of 103 self storage properties containing approximately 7.8 million rentable square feet, configured in approximately 63,000 storage units and located across 17 states. 2016 Joint Venture As of September 30, 2020, the Company's unconsolidated real estate venture, formed in September 2016 with a state pension fund advised by Heitman Capital Management LLC (the "2016 Joint Venture"), owned and operated a portfolio of 74 properties containing approximately 4.9 million rentable square feet, configured in approximately 40,000 storage units and located across 13 states. The 2016 Joint Venture acquired two self storage properties for $12.1 million during the nine months ended September 30, 2020. The 2016 Joint Venture financed these acquisitions with capital contributions from the 2016 Joint Venture members, of which the Company contributed $3.1 million for its 25% proportionate share. The following table presents the combined condensed financial position of the Company's unconsolidated real estate ventures as of September 30, 2020 and December 31, 2019 (in thousands): September 30, 2020 December 31, 2019 ASSETS Self storage properties, net $ 1,803,992 $ 1,835,235 Other assets 26,094 22,413 Total assets $ 1,830,086 $ 1,857,648 LIABILITIES AND EQUITY Debt financing $ 989,819 $ 989,182 Other liabilities 23,462 20,487 Equity 816,805 847,979 Total liabilities and equity $ 1,830,086 $ 1,857,648 The following tables present the combined condensed operating information of the Company's unconsolidated real estate ventures for the three and nine months ended September 30, 2020 and 2019 (in thousands): Three Months Ended September 30, 2020 2019 Total revenue $ 41,878 $ 41,600 Property operating expenses 13,005 12,727 Net operating income 28,873 28,873 Supervisory, administrative and other expenses (2,780) (2,750) Depreciation and amortization (15,320) (20,788) Interest expense (10,303) (9,934) Acquisition and other expenses (381) (314) Net income (loss) $ 89 $ (4,913) Nine Months Ended September 30, 2020 2019 Total revenue $ 121,846 $ 122,253 Property operating expenses 37,554 37,815 Net operating income 84,292 84,438 Supervisory, administrative and other expenses (8,089) (8,109) Depreciation and amortization (45,711) (64,502) Interest expense (30,867) (29,895) Loss on sale of self storage properties — (806) Acquisition and other expenses (800) (1,141) Net loss $ (1,175) $ (20,015)

ACQUISITIONS

ACQUISITIONS	9 Months Ended
	Sep. 30, 2020
Asset Acquisitions And Dispositions [Abstract]
ACQUISITIONS	ACQUISITIONS Self Storage Property Acquisitions The Company acquired 44 self storage properties with an estimated fair value of $282.8 million during the nine months ended September 30, 2020. Of these acquisitions, five self storage properties with an estimated fair value of $44.3 million were acquired by the Company from its PROs. The 44 self storage property acquisitions were accounted for as asset acquisitions and accordingly, $3.3 million of transaction costs related to the acquisitions were capitalized as part of the basis of the acquired properties. The Company recognized the estimated fair value of the acquired assets and assumed liabilities on the respective dates of such acquisitions. The Company allocated the total purchase price to the estimated fair value of tangible and intangible assets acquired and liabilities assumed. The Company allocated a portion of the purchase price to identifiable intangible assets consisting of customer in-place leases which were recorded at estimated fair value of $6.0 million, resulting in a total fair value of $276.8 million allocated to real estate. The following table summarizes the investment in self storage property acquisitions completed by the Company during the nine months ended September 30, 2020 (dollars in thousands): Acquisitions Closed During the Three Months Ended: Number of Properties Summary of Investment Cash and Acquisition Costs Value of OP Equity (1) Other Liabilities Total March 31, 2020 36 $ 214,584 $ 7,217 $ 972 $ 222,773 June 30, 2020 4 30,198 5,842 207 36,247 September 30, 2020 4 20,173 3,427 204 23,804 Total 44 $ 264,955 $ 16,486 $ 1,383 $ 282,824 (1) Value of OP equity represents the fair value of LTIP units, OP units and subordinated performance units. Acquisition of PRO Management Company As discussed in Note 1 and Note 3, on March 31, 2020, the Company closed on the previously announced mergers of SecurCare and DLAN with and into wholly-owned subsidiaries of the Company. The mergers were accounted for as a business combination whereby the Company acquired additional interests in its operating partnership and DownREIT partnerships. Accordingly, this portion of the transaction was accounted for as a change in ownership of a consolidated subsidiary, resulting in a reduction to noncontrolling interests equal to the net book value of the acquired subsidiary interests. In connection with the mergers, SecurCare's property management platform and related intellectual property were internalized by the Company. Under the terms of the Company's facilities portfolio management agreement with SecurCare, in connection with a retirement event leading to the internalization of SecurCare's property management platform, SecurCare was entitled to receive OP units in exchange for its property management platform and related intellectual property based on a contractual formula. Using this formula, the Company determined that SecurCare was entitled to receive an equivalent of 348,020 OP units totaling $10.3 million, based on the acquisition date closing price of the Company's common shares. The Company allocated the total purchase price to the estimated fair value of tangible and intangible assets acquired, and liabilities assumed. The Company allocated a portion of the purchase price to tangible fixed assets of $0.1 million and intangible assets consisting of a management contract with an estimated fair value of $4.6 million and the SecurCare trade name with an estimated fair value of $3.2 million. The excess of the aggregate consideration paid over the identified assets acquired and liabilities assumed, equal to $2.4 million, was allocated to goodwill. The tangible and intangible assets related to the internalization are reported in other assets, net in the Company's condensed consolidated balance sheets. The Company’s fair value measurements were based, in part, on valuations prepared by an independent valuation firm and the allocation of the purchase price required a significant amount of judgment. The Company measured the fair value of the management contract asset based on discounted future cash flows expected under the management contract from a market participant perspective. The management contract asset will be charged to amortization expense on a straight-line basis over 15 years, which represents the time period over which the majority of value was attributed in the Company’s discounted cash flow model. The Company measured the fair value of the trade name, which has an indefinite life and is not amortized, using the relief from royalty method. The allocation of the purchase price requires judgment and was based on the Company's valuations, estimates and assumptions of the acquisition date fair value of the tangible and intangible assets acquired and liabilities assumed.

OTHER ASSETS

OTHER ASSETS	9 Months Ended
	Sep. 30, 2020
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
OTHER ASSETS	OTHER ASSETS Other assets consist of the following (dollars in thousands): September 30, 2020 December 31, 2019 Customer in-place leases, net of accumulated amortization of $4,156 and $7,267, respectively $ 2,694 $ 3,704 Receivables: Trade, net 2,479 2,809 PROs and other affiliates 2,641 2,773 Receivables from unconsolidated real estate ventures 5,154 4,765 Property acquisition and other deposits 550 4,438 Interest rate swaps — 980 Equity securities — 7,703 Prepaid expenses and other 6,320 4,762 Corporate furniture, equipment and other, net 1,825 1,925 Trade names 6,380 3,200 Management contracts, net of accumulated amortization of $2,969 and $2,274, respectively 12,251 8,349 Tenant reinsurance intangible, net of accumulated amortization of $756 and $317, respectively 13,844 14,283 Goodwill 8,182 5,750 Total $ 62,320 $ 65,441 Amortization expense related to customer in-place leases amounted to $1.7 million and $3.3 million for the three months ended September 30, 2020 and 2019, respectively, and $7.0 million and $8.6 million during the nine months ended September 30, 2020 and 2019, respectively. Amortization expense related to management contracts amounted to $0.2 million and $0.2 million for the three months ended September 30, 2020 and 2019, respectively, and $0.7 million and $0.6 million during the nine months ended September 30, 2020 and 2019, respectively. Amortization expense related to the tenant reinsurance intangible amounted to $0.1 million and $0.2 million for the three months ended September 30, 2020 and 2019, respectively, and $0.3 million and $0.2 million during the nine months ended September 30, 2020 and 2019, respectively.

DEBT FINANCING

DEBT FINANCING	9 Months Ended
	Sep. 30, 2020
Debt Disclosure [Abstract]
DEBT FINANCING	DEBT FINANCING The Company's outstanding debt as of September 30, 2020 and December 31, 2019 is summarized as follows (dollars in thousands): Interest Rate (1) September 30, 2020 December 31, 2019 Credit Facility: Revolving line of credit 1.45% $ 246,500 $ — Term loan A 3.74% 125,000 125,000 Term loan B 2.91% 250,000 250,000 Term loan C 2.80% 225,000 225,000 Term loan D 3.57% 175,000 175,000 2023 Term loan facility 2.83% 175,000 175,000 2028 Term loan facility 4.62% 75,000 75,000 2029 Term loan facility 4.27% 100,000 100,000 2029 Senior Unsecured Notes 3.98% 100,000 100,000 2031 Senior Unsecured Notes 4.08% 50,000 50,000 Fixed rate mortgages payable 4.26% 224,653 264,260 Total principal 1,746,153 1,539,260 Unamortized debt issuance costs and debt premium, net (4,450) (5,213) Total debt $ 1,741,703 $ 1,534,047 (1) Represents the effective interest rate as of September 30, 2020. Effective interest rate incorporates the stated rate plus the impact of interest rate cash flow hedges and discount and premium amortization, if applicable. For the revolving line of credit, the effective interest rate excludes fees for unused borrowings. As of September 30, 2020, the Company's unsecured credit facility provided for total borrowings of $1.275 billion (the "credit facility"). The credit facility consists of the following components: (i) a revolving line of credit (the "Revolver") which provides for a total borrowing commitment up to $500.0 million, under which the Company may borrow, repay and re-borrow amounts, (ii) a $125.0 million tranche A term loan facility (the "Term Loan A"), (iii) a $250.0 million tranche B term loan facility (the "Term Loan B"), (iv) a $225.0 million tranche C term loan facility (the "Term Loan C"), and (v) a $175.0 million tranche D term loan facility (the "Term Loan D"). As of September 30, 2020, the Company had an expansion option under the credit facility, which, if exercised in full, would provide for a total credit facility of $1.750 billion. As of September 30, 2020, the Company had outstanding letters of credit totaling $5.7 million and would have had the capacity to borrow remaining Revolver commitments of $247.8 million while remaining in compliance with the credit facility's financial covenants. At September 30, 2020, the Company was in compliance with all such covenants. For a summary of the Company's financial covenants and additional detail regarding the Company's credit facility, 2023 Term Loan Facility, 2028 Term Loan Facility, 2029 Term Loan Facility, 2029 Senior Unsecured Notes, 2031 Senior Unsecured Notes and fixed rate mortgages payable, please see Note 8 to the Company's most recent Annual Report on Form 10-K for the year ended December 31, 2019 filed with the SEC. 2030 And 2032 Senior Unsecured Notes As discussed in Note 14, on October 22, 2020, the operating partnership issued $150.0 million of 2.99% senior unsecured notes due August 5, 2030 (the "2030 Notes") and $100.0 million of 3.09% senior unsecured notes due August 5, 2032 (the "2032 Notes") in a private placement to certain institutional investors. Future Debt Obligations Based on existing debt agreements in effect as of September 30, 2020, the scheduled principal and maturity payments for the Company's outstanding borrowings are presented in the table below (in thousands): Year Ending December 31, Scheduled Principal and Maturity Payments Amortization of Premium and Unamortized Debt Issuance Costs Total Remainder of 2020 $ 1,040 $ (381) $ 659 2021 7,603 (1,522) 6,081 2022 4,205 (1,512) 2,693 2023 377,049 (1,159) 375,890 2024 518,464 (790) 517,674 2025 227,185 (218) 226,967 Thereafter 610,607 1,132 611,739 $ 1,746,153 $ (4,450) $ 1,741,703

EARNINGS PER SHARE

EARNINGS PER SHARE	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
EARNINGS PER SHARE	EARNINGS PER SHARE The following table sets forth the computation of basic and diluted earnings (loss) per common share for the three and nine months ended September 30, 2020 and 2019 (in thousands, except per share amounts): Three Months Ended Nine Months Ended 2020 2019 2020 2019 Earnings (loss) per common share - basic and diluted Numerator Net income $ 21,411 $ 16,514 $ 54,961 $ 47,187 Net income attributable to noncontrolling interests (7,924) (25,374) (24,404) (56,292) Net income (loss) attributable to National Storage Affiliates Trust 13,487 (8,860) 30,557 (9,105) Distributions to preferred shareholders (3,275) (3,272) (9,822) (9,117) Distributed and undistributed earnings allocated to participating securities (11) (8) (34) (26) Net income (loss) attributable to common shareholders - basic and diluted $ 10,201 $ (12,140) $ 20,701 $ (18,248) Denominator Weighted average shares outstanding - basic and diluted 68,887 59,278 65,643 57,835 Earnings (loss) per share - basic and diluted $ 0.15 $ (0.20) $ 0.32 $ (0.32) As discussed in Note 2, the Company allocates GAAP income (loss) utilizing the HLBV method, in which the Company allocates income or loss based on the change in each unitholders' claim on the net assets of its operating partnership at period end after adjusting for any distributions or contributions made during such period. Due to the stated liquidation priorities and because the HLBV method incorporates non-cash items such as depreciation expense, in any given period, income or loss may be allocated disproportionately to National Storage Affiliates Trust and noncontrolling interests, resulting in volatile fluctuations of basic and diluted earnings (loss) per share. Outstanding equity interests of the Company's operating partnership and DownREIT partnerships are considered potential common shares for purposes of calculating diluted earnings (loss) per share as the unitholders may, through the exercise of redemption rights, obtain common shares, subject to various restrictions. Basic earnings per share is calculated based on the weighted average number of common shares outstanding during the period. Diluted earnings per share is calculated by further adjusting for the dilutive impact using the treasury stock method for unvested LTIP units subject to a service condition outstanding during the period and the if-converted method for any convertible securities outstanding during the period. Generally, following certain lock-out periods, OP units in the Company's operating partnership are redeemable for cash or, at the Company's option, exchangeable for common shares on a one-for-one basis, subject to certain adjustments and DownREIT OP units are redeemable for cash or, at the Company's option, exchangeable for OP units in its operating partnership on a one-for-one basis, subject to certain adjustments in each case. LTIP units may also, under certain circumstances, be convertible into OP units on a one-for-one basis, which are then exchangeable for common shares as described above. Certain LTIP units vested prior to or upon the completion of the Company's initial public offering and certain LTIP units have vested upon the satisfaction of a service or market condition or will vest upon the satisfaction of future service and market conditions. Vested LTIP units and unvested LTIP units that vest based on a service or market condition are allocated income or loss in a similar manner as OP units. Unvested LTIP units subject to a service or market condition are evaluated for dilution using the treasury stock method. For the three and nine months ended September 30, 2020, 420,280 unvested LTIP units that vest based on a service or market condition are excluded from the calculation of diluted earnings (loss) per share as they are not dilutive to earnings (loss) per share. In addition, certain LTIP units vest upon the future acquisition of properties sourced by PROs or the completion of expansion projects. For the three and nine months ended September 30, 2020, 252,894 unvested LTIP units that vest upon the future acquisition of properties, or the completion of expansion projects, are excluded from the calculation of diluted earnings (loss) per share because the contingency for the units to vest has not been attained as of the end of the reported periods. Subordinated performance units may also, under certain circumstances, be convertible into OP units which are exchangeable for common shares as described above, and DownREIT subordinated performance units may, under certain circumstances, be exchangeable for subordinated performance units on a one-for-one basis. Subordinated performance units are only convertible into OP units, after a two two two For the three months ended September 30, 2020 and 2019, potential common shares totaling 47.0 million and 55.2 million, respectively, related to OP units, DownREIT OP units, subordinated performance units, DownREIT subordinated performance units and vested LTIP units have been excluded from the calculation of diluted earnings (loss) per share as they are not dilutive to earnings (loss) per share. For the nine months ended September 30, 2020 and 2019, potential common shares totaling 48.3 million and 53.9 million, respectively, related to OP units, DownREIT OP units, subordinated performance units, DownREIT subordinated performance units and vested LTIP units have been excluded from the calculation of diluted earnings (loss) per share as they are not dilutive to earnings (loss) per share. Participating securities, which consist of unvested restricted common shares, receive dividends equal to those received by common shares. The effect of participating securities for the periods presented above is calculated using the two-class method of allocating distributed and undistributed earnings.

RELATED PARTY TRANSACTIONS

RELATED PARTY TRANSACTIONS	9 Months Ended
	Sep. 30, 2020
Related Party Transactions [Abstract]
RELATED PARTY TRANSACTIONS	RELATED PARTY TRANSACTIONS Supervisory and Administrative Fees For the self storage properties that are managed by the PROs, the Company has entered into asset management agreements with the PROs to provide leasing, operating, supervisory and administrative services. The asset management agreements generally provide for fees ranging from 5% to 6% of gross revenue for the managed self storage properties. During the three months ended September 30, 2020 and 2019, the Company incurred $3.7 million and $5.2 million, respectively, for supervisory and administrative fees to the PROs and during the nine months ended September 30, 2020 and 2019, the Company incurred $12.5 million and $14.8 million, respectively, for supervisory and administrative fees to the PROs. Such fees are included in general and administrative expenses in the accompanying condensed consolidated statements of operations. Payroll Services For the self storage properties that are managed by the PROs, the employees responsible for operations are employees of the PROs who charge the Company for the costs associated with the respective employees. For the three months ended September 30, 2020 and 2019, the Company incurred $5.7 million and $8.1 million, respectively, for payroll and related costs reimbursable to these PROs and for the nine months ended September 30, 2020 and 2019, the Company incurred $20.0 million and $23.8 million, respectively, for payroll and related costs reimbursable to these PROs. Such costs are included in property operating expenses in the accompanying condensed consolidated statements of operations. Due Diligence Costs During the three months ended September 30, 2019, the Company incurred $0.1 million of expenses payable to certain PROs related to self storage property acquisitions sourced by the PROs and during the nine months ended September 30, 2020 and 2019, the Company incurred $0.2 million and $0.7 million, respectively, of expenses payable to certain PROs related to self storage property acquisitions sourced by the PROs. These expenses, which are based on the volume of transactions sourced by the PROs, are intended to reimburse the PROs for due diligence costs incurred in the sourcing and underwriting process. These due diligence costs are capitalized as part of the basis of the acquired self storage properties. Self Storage Property Acquisitions During the nine months ended September 30, 2020, the Company acquired one self storage property for $7.5 million from an entity that was partially owned by Arlen Nordhagen, the Company's executive chairman and former chief executive officer, and David Cramer, the Company's chief operating officer. Of the total consideration paid, Mr. Nordhagen's and Mr. Cramer's interest was approximately 58,376 OP Units with a value of $1.5 million and 29,689 OP Units with a value $0.7 million, respectively. During the nine months ended September 30, 2020, the Company acquired one self storage property for $6.6 million from a company in which an entity controlled by J. Timothy Warren, a trustee of the Company, was an investor. Mr. Warren's adult children held an ownership interest in such entity. Of the total consideration paid, the interest of Mr. Warren's children was approximately 15,512 OP Units with a value of $0.4 million.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	9 Months Ended
	Sep. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIESLegal Proceedings The Company is subject to litigation, claims, and assessments that may arise in the ordinary course of its business activities. Such matters include contractual matters, employment related issues, and regulatory proceedings. Although occasional adverse decisions or settlements may occur, the Company believes that the final disposition of such matters will not have a material adverse effect on the Company's financial position, results of operations, or liquidity.

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS Recurring Fair Value Measurements The Company sometimes limits its exposure to interest rate fluctuations by entering into interest rate swap agreements. The interest rate swap agreements moderate the Company's exposure to interest rate risk by effectively converting the interest on variable rate debt to a fixed rate. The Company measures its interest rate swap derivatives at fair value on a recurring basis. The changes in the fair value of derivatives designated and that qualify as cash flow hedges are recorded in accumulated other comprehensive income (loss) and are subsequently reclassified into earnings in the period that the hedged transaction affects earnings. Information regarding the Company's interest rate swaps measured at fair value, which are classified within Level 2 of the GAAP fair value hierarchy, is presented below (dollars in thousands): Fair value at December 31, 2018 $ 14,195 Gains on interest rate swaps reclassified into interest expense from accumulated other comprehensive (loss) income (3,492) Unrealized losses on interest rate swaps included in accumulated other comprehensive (loss) income (44,547) Fair value at September 30, 2019 $ (33,844) Fair value at December 31, 2019 $ (19,083) Losses on interest rate swaps reclassified into interest expense from accumulated other comprehensive (loss) income 9,519 Unrealized losses on interest rate swaps included in accumulated other comprehensive (loss) income (77,354) Fair value at September 30, 2020 $ (86,918) As of September 30, 2020 and December 31, 2019, the Company had outstanding interest rate swaps with aggregate notional amounts of $1,125.0 million and $1,125.0 million, respectively, designated as cash flow hedges. As of September 30, 2020, the Company's swaps had a weighted average remaining term of approximately 3.5 years. The fair value of these swaps are presented as interest rate swap liabilities in the Company's balance sheets, and the Company recognizes any changes in the fair value as an adjustment of accumulated other comprehensive income (loss) within equity. If the forward rates at September 30, 2020 remain constant, the Company estimates that during the next 12 months, the Company would reclassify into earnings approximately $20.0 million of the unrealized losses included in accumulated other comprehensive income (loss). If market interest rates increase above the 1.90% weighted average fixed rate under these interest rate swaps, the Company will benefit from net cash payments due from its counterparties to the interest rate swaps. There were no transfers between levels of the three-tier fair value measurement hierarchy during the nine months ended September 30, 2020 and 2019. For financial assets and liabilities that utilize Level 2 inputs, the Company utilizes both direct and indirect observable price quotes, including LIBOR yield curves. The Company uses valuation techniques for Level 2 financial assets and liabilities which include LIBOR yield curves at the reporting date as well as assessing counterparty credit risk. Counterparties to these contracts are highly rated financial institutions. 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 the Company's derivatives utilize Level 3 inputs, such as estimates of current credit spreads, to evaluate the likelihood of default by the Company and the counterparties. As of September 30, 2020, the Company determined that the effect of credit valuation adjustments on the overall valuation of its derivative positions are not significant to the overall valuation of its derivatives. Therefore, the Company has determined that its derivative valuations are appropriately classified in Level 2 of the fair value hierarchy. Fair Value Disclosures The carrying values of cash and cash equivalents, restricted cash, trade receivables, and accounts payable and accrued liabilities reflected in the balance sheets at September 30, 2020 and December 31, 2019, approximate fair value due to the short term nature of these financial assets and liabilities. The carrying value of variable rate debt financing reflected in the balance sheets at September 30, 2020 and December 31, 2019 approximates fair value as the changes in their associated interest rates reflect the current market and credit risk is similar to when the loans were originally obtained. The combined principal balance of the Company's fixed rate mortgages payable was approximately $224.7 million as of September 30, 2020 with a fair value of approximately $252.9 million (categorized within Level 2 of the fair value hierarchy). In determining the fair value, the Company estimated a weighted average market interest rate of approximately 2.06%, compared to the weighted average contractual interest rate of 4.69%. The combined

LEASES

LEASES	9 Months Ended
	Sep. 30, 2020
Leases [Abstract]
LEASES	LEASES The Company determines if a contractual arrangement is a lease at inception. As a lessee, the Company has non-cancelable lease agreements for real estate and its corporate office space that are classified as operating leases. The Company's operating leases are included in operating lease right-of-use ("ROU") assets and operating lease liabilities in its condensed consolidated balance sheets. Operating lease ROU assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. As the Company's operating leases do not provide an implicit rate, the Company used its incremental borrowing rate based on the information available at commencement date in determining the discount rate for the present value of the lease payments. To the extent that the lease agreements provide for fixed increases throughout the term of the lease, the Company recognizes lease expense on a straight-line basis over the expected lease terms. Real Estate Leasehold Interests The Company has eight properties that are subject to non-cancelable leasehold interest agreements with remaining lease terms ranging from 14 to 72 years, inclusive of extension options that the Company anticipates exercising. Rent expense under these leasehold interest agreements is included in property operating expenses in the accompanying condensed consolidated statements of operations and amounted to $0.4 million and $0.4 million for the three months ended September 30, 2020 and 2019, respectively, and $1.3 million and $1.2 million for the nine months ended September 30, 2020 and 2019, respectively. Office Leases The Company has entered into non-cancelable lease agreements for its corporate office space with remaining lease terms ranging from two The weighted-average remaining lease term and the weighted-average discount rate for the Company's operating leases as of September 30, 2020 are as follows: September 30, 2020 Weighted-average remaining lease term Real estate leasehold interests 28 years Office leases 7 years Weighted-average remaining discount rate Real estate leasehold interests 4.9 % Office leases 3.8 % As of September 30, 2020, the future minimum lease payments under the Company's operating leases, for which the Company is a lessee, are as follows (in thousands): Year Ending December 31, Real Estate Leasehold Interests Office Leases Total Remainder of 2020 $ 357 $ 106 $ 463 2021 1,444 471 1,915 2022 1,459 465 1,924 2023 1,464 430 1,894 2024 1,470 450 1,920 2025 through 2092 36,728 1,080 37,808 Total lease payments $ 42,922 $ 3,002 $ 45,924 Less imputed interest (20,640) (355) (20,995) Total $ 22,282 $ 2,647 $ 24,929 As of December 31, 2019, the future minimum lease payments under the Company's operating leases, for which the Company is a lessee, are as follows (in thousands): Year Ending December 31, Real Estate Leasehold Interests Office Leases Total 2020 $ 1,419 $ 286 $ 1,705 2021 1,444 387 1,831 2022 1,459 381 1,840 2023 1,464 346 1,810 2024 1,470 353 1,823 2025 through 2092 36,728 691 37,419 Total lease payments $ 43,984 $ 2,444 $ 46,428 Less imputed interest (21,440) (323) (21,763) Total $ 22,544 $ 2,121 $ 24,665

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	9 Months Ended
	Sep. 30, 2020
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTS 2030 And 2032 Senior Unsecured Notes On October 22, 2020, the operating partnership issued $150.0 million of 2.99% senior unsecured notes due August 5, 2030 (the "2030 Notes") and $100.0 million of 3.09% senior unsecured notes due August 5, 2032 (the "2032 Notes") in a private placement to certain institutional investors. The senior unsecured notes are governed by the previously disclosed Note Purchase Agreement dated August 4, 2020 (the "Note Purchase Agreement"), by and among the operating partnership as issuer, the Company, and the purchasers of the senior unsecured notes. The Company used the proceeds to repay outstanding amounts on its Revolver. Interest is payable semiannually, on August 30th and February 28th of each year, commencing on February 28, 2021. The senior unsecured notes are senior unsecured obligations of the Company and are jointly and severally guaranteed by certain of the Company's subsidiaries, as subsidiary guarantors. The senior unsecured notes rank pari passu with the credit facility, 2023 Term Loan Facility, 2028 Term Loan Facility, 2029 Term Loan Facility, 2029 Senior Unsecured Notes and 2031 Senior Unsecured Notes. The Note Purchase Agreement contains financial covenants that are substantially similar to those of the Company's credit facility. In addition, the terms of the Note Purchase Agreement contain customary affirmative and negative covenants that, among other things, limit the Company's ability to make distributions or certain investments, incur debt, incur liens and enter into certain transactions.

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated financial statements are presented on the accrual basis of accounting in accordance with U.S. generally accepted accounting principles ("GAAP") and have been prepared by the Company pursuant to the rules and regulations of the Securities and Exchange Commission (the "SEC") regarding interim financial reporting. Accordingly, certain information and footnote disclosures required by GAAP for
Principles of Consolidation	Principles of ConsolidationThe Company's financial statements include the accounts of its operating partnership and its controlled subsidiaries. All significant intercompany balances and transactions have been eliminated in the consolidation of entities.
Variable Interest Entities	When the Company obtains an economic interest in an entity, the Company evaluates the entity to determine if the entity is deemed a variable interest entity ("VIE"), and if the Company is deemed to be the primary beneficiary, in accordance with authoritative guidance issued on the consolidation of VIEs. When an entity is not deemed to be a VIE, the Company considers the provisions of additional guidance to determine whether the general partner controls a limited partnership or similar entity when the limited partners have certain rights. The Company consolidates all entities that are VIEs and of which the Company is deemed to be the primary beneficiary. The Company has determined that its operating partnership is a VIE. The sole significant asset of National Storage Affiliates Trust is its investment in its operating partnership, and consequently, substantially all of the Company’s assets and liabilities represent those assets and liabilities of its operating partnership.
Reclassifications	Reclassifications Certain amounts in the condensed consolidated financial statements and related notes have been reclassified to conform to the current year presentation. Such reclassifications do not impact the Company's previously reported financial position or net income (loss).
Revenue Recognition - Rental revenue	Rental revenueRental revenue consists of space rentals and related fees. Management has determined that all of the Company's leases are operating leases. Substantially all leases may be terminated on a month-to-month basis and rental income is recognized ratably over the lease term using the straight-line method. Rents received in advance are deferred and recognized on a straight-line basis over the related lease term associated with the prepayment. Promotional discounts and other incentives are recognized as a reduction to rental income over the applicable lease term.
Revenue Recognition - Other property-related revenue, management fees and other revenue	Other property-related revenue Other property-related revenue primarily consists of ancillary revenues such as tenant insurance and/or tenant warranty protection-related access fees, sales of storage supplies and truck rentals which are recognized in the period earned. The Company and certain of the Company’s PROs have tenant insurance- and/or tenant warranty protection plan-related arrangements with insurance companies and the Company’s tenants. During the three months ended September 30, 2020 and 2019, the Company recognized $2.9 million and $2.4 million, respectively, of tenant insurance and tenant warranty protection plan revenues and during the nine months ended September 30, 2020 and 2019, the Company recognized $8.2 million and $6.7 million, respectively, of tenant insurance and tenant warranty protection plan revenues. The Company sells boxes, packing supplies, locks, other retail merchandise and rents moving trucks at its properties. During the three months ended September 30, 2020 and 2019, the Company recognized retail sales of $0.6 million and $0.4 million, respectively, and during the nine months ended September 30, 2020 and 2019, the Company recognized retail sales of $1.4 million and $1.3 million, respectively. Management fees and other revenue Management fees and other revenue consist of property management fees, platform fees, call center fees, acquisition fees, and a portion of tenant warranty protection or tenant insurance proceeds that the Company earns for managing and operating its unconsolidated real estate ventures. With respect to both the 2018 Joint Venture and the 2016 Joint Venture (as each is defined in Note 5), the Company provides supervisory and administrative property management services, centralized call center services, and technology platform and revenue management services to the properties in the unconsolidated real estate ventures. The property management fees are equal to 6% of monthly gross revenues and net sales revenues from the assets of the unconsolidated real estate ventures, and the platform fees are equal to $1,250 per month per unconsolidated real estate venture property. With respect to the 2016 Joint Venture only, the call center fees are equal to 1% of each of monthly gross revenues and net sales revenues from the 2016 Joint Venture properties. During the three months ended September 30, 2020 and 2019, the Company recognized property management fees, call center fees and platform fees of $3.4 million and $3.3 million, respectively, and during the nine months ended September 30, 2020 and 2019, the Company recognized property management fees, call center fees and platform fees of $9.8 million and $9.7 million, respectively. For acquisition fees, the Company provides sourcing, underwriting and administration services to the unconsolidated real estate ventures. The 2016 Joint Venture paid the Company a $4.1 million acquisition fee equal to 0.65% of the gross capitalization (including debt and equity) of the original 66-property 2016 Joint Venture portfolio (the "Initial 2016 JV Portfolio") in 2016, at the time of the Initial 2016 JV Portfolio acquisition. The 2018 Joint Venture paid the Company a $4.0 million acquisition fee related to the initial acquisition of properties by the 2018 Joint Venture (the "Initial 2018 JV Portfolio") in 2018, at the time of the Initial 2018 JV Portfolio acquisition. These fees are refundable to the unconsolidated real estate ventures, on a prorated basis, if the Company is removed as the managing member during the initial four four The Company also earns acquisition fees for properties acquired by the unconsolidated real estate ventures subsequent to the Initial 2016 JV Portfolio and the Initial 2018 JV Portfolio. These fees are based on a percentage of the gross capitalization of the acquired assets determined by the members of the 2016 Joint Venture and the 2018 Joint Venture, and are generally earned when the unconsolidated real estate ventures obtain title and control of an acquired property. During the three months ended September 30, 2020 and 2019, the Company recognized acquisition fees of $0.5 million and $0.4 million, respectively, and during the nine months ended September 30, 2020 and 2019, the Company recognized acquisition fees of $1.4 million and $1.4 million, respectively. An affiliate of the Company facilitates tenant warranty protection or tenant insurance programs for tenants of the properties in the unconsolidated real estate ventures in exchange for 50% of all proceeds from such programs at each unconsolidated real estate venture property. During the three months ended September 30, 2020 and 2019, the Company recognized $2.0 million and $1.2 million, respectively, of revenue related to these activities and during the nine months ended September 30, 2020 and 2019, the Company recognized $5.5 million and $3.6 million, respectively, of revenue related to these activities.
Gain on sale of self storage properties	Gain on sale of self storage propertiesThe Company recognizes gains from disposition of facilities only upon closing in accordance with the guidance on sales of nonfinancial assets. Profit on real estate sold is recognized upon closing when all, or substantially all, of the promised consideration has been received and is nonrefundable and the Company has transferred control of the facilities to the purchaser.
Investments in Unconsolidated Real Estate Ventures	Investments in Unconsolidated Real Estate Ventures The Company’s investments in its unconsolidated real estate ventures are recorded under the equity method of accounting in the accompanying condensed consolidated financial statements. Under the equity method, the Company’s investments in unconsolidated real estate ventures are stated at cost and adjusted for the Company’s share of net earnings or losses and reduced by distributions. Equity in earnings (losses) is recognized based on the
Noncontrolling Interests	Noncontrolling Interests All of the limited partner equity interests ("OP equity") in the operating partnership not held by the Company are reflected as noncontrolling interests. Noncontrolling interests also include ownership interests in DownREIT partnerships held by entities other than the operating partnership or its subsidiaries. In the condensed consolidated statements of operations, the Company allocates net income (loss) attributable to noncontrolling interests to arrive at net income (loss) attributable to National Storage Affiliates Trust. For transactions that result in changes to the Company's ownership interest in its operating partnership, the carrying amount of noncontrolling interests is adjusted to reflect such changes. The difference between the fair value of the consideration received or paid and the amount by which the noncontrolling interest is adjusted is reflected as an adjustment to additional paid-in capital on the condensed consolidated balance sheets.
Allocation of Net Income (Loss)	Allocation of Net Income (Loss) The distribution rights and priorities set forth in the operating partnership's LP Agreement differ from what is reflected by the underlying percentage ownership interests of the unitholders. Accordingly, the Company allocates GAAP income (loss) utilizing the hypothetical liquidation at book value ("HLBV") method, in which the Company allocates income or loss based on the change in each unitholders’ claim on the net assets of its operating partnership at period end after adjusting for any distributions or contributions made during such period. The HLBV method is commonly applied to equity investments where cash distribution percentages vary at different points in time and are not directly linked to an equity holder’s ownership percentage. The HLBV method is a balance sheet-focused approach to income (loss) allocation. A calculation is prepared at each balance sheet date to determine the amount that unitholders would receive if the operating partnership were to liquidate all of its assets (at GAAP net book value) and distribute the resulting proceeds to its creditors and unitholders based on the contractually defined liquidation priorities. The difference between the calculated liquidation distribution amounts at the beginning and the end of the reporting period, after adjusting for capital contributions and distributions, is used to derive each unitholder's share of the income (loss) for the period. Due to the stated liquidation priorities and because the HLBV method incorporates non-cash items such as depreciation expense, in any given period, income or loss may be allocated disproportionately to unitholders as compared to their respective ownership percentage in the operating partnership, and net income (loss) attributable to National Storage Affiliates Trust could be more or less net income than actual cash distributions received and more or less income or loss than what may be received in the event of an actual liquidation. Additionally, the HLBV method could result in net income (or net loss) attributable to National Storage Affiliates Trust during a period when the Company reports consolidated net loss (or net income), or net income (or net loss) attributable to National Storage Affiliates Trust in excess of the Company's consolidated net income (or net loss). The computations of basic and diluted earnings (loss) per share may be materially affected by these disproportionate income (loss) allocations, resulting in volatile fluctuations of basic and diluted earnings (loss) per share.
Other Comprehensive Income (Loss)	Other Comprehensive Income (Loss)The Company has cash flow hedge derivative instruments that are measured at fair value with unrealized gains or losses recognized in other comprehensive income (loss) with a corresponding adjustment to accumulated other comprehensive income (loss) within equity, as discussed further in Note 12. Under the HLBV method of allocating income (loss) discussed above, a calculation is prepared at each balance sheet date by applying the HLBV method including, and excluding, the assets and liabilities resulting from the Company's cash flow hedge derivative instruments to determine comprehensive income (loss) attributable to National Storage Affiliates Trust. As a result of the distribution rights and priorities set forth in the operating partnership's LP Agreement, in any given period, other comprehensive income (loss) may be allocated disproportionately to unitholders as compared to their respective ownership percentage in the operating partnership and as compared to their respective allocation of net income (loss).
Restricted Cash	Restricted CashThe Company's restricted cash consists of escrowed funds deposited with financial institutions for real estate taxes, insurance and other reserves for capital improvements in accordance with the Company's loan agreements
Use of Estimates	Use of EstimatesThe preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In March 2020, the Financial Accounting Standards Board issued ASU 2020-04, Reference Rate Reform (Topic 848). ASU 2020-04 contains practical expedients for reference rate reform related activities that impact debt, leases, derivatives and other contracts. The guidance in ASU 2020-04 is optional and may be elected over time as reference rate reform activities occur. During the nine months ended September 30, 2020, the Company elected to apply the hedge accounting expedients related to probability and the assessments of effectiveness for future LIBOR-indexed cash flows to assume that the index upon which future hedged transactions will be based matches the index on the corresponding derivatives. Application of these expedients preserves the presentation of derivatives consistent with past presentation. The Company continues to evaluate the impact of the guidance and may apply other elections as applicable as additional changes in the market occur. See Note 12 for additional detail about the Company's derivatives.

SHAREHOLDERS' EQUITY AND NONC_2

SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS (Tables)	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Schedule of noncontrolling interests	As of September 30, 2020 and December 31, 2019, units reflecting noncontrolling interests consisted of the following: September 30, 2020 December 31, 2019 Series A-1 preferred units 637,382 642,982 OP units 29,443,460 30,188,305 Subordinated performance units 8,770,744 11,014,195 LTIP units 765,840 743,566 DownREIT units DownREIT OP units 1,924,918 1,848,261 DownREIT subordinated performance units 4,337,111 4,371,622 Total 45,879,455 48,808,931

SELF STORAGE PROPERTIES (Tables

SELF STORAGE PROPERTIES (Tables)	9 Months Ended
	Sep. 30, 2020
Real Estate [Abstract]
Schedule of self storage properties	Self storage properties are summarized as follows (dollars in thousands): September 30, 2020 December 31, 2019 Land $ 690,581 $ 649,938 Buildings and improvements 2,683,288 2,435,171 Furniture and equipment 7,549 6,610 Total self storage properties 3,381,418 3,091,719 Less accumulated depreciation (416,423) (337,822) Self storage properties, net $ 2,964,995 $ 2,753,897

INVESTMENT IN UNCONSOLIDATED _2

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES (Tables)	9 Months Ended
	Sep. 30, 2020
Equity Method Investments and Joint Ventures [Abstract]
Schedule of condensed financial information of unconsolidated real estate ventures	The following table presents the combined condensed financial position of the Company's unconsolidated real estate ventures as of September 30, 2020 and December 31, 2019 (in thousands): September 30, 2020 December 31, 2019 ASSETS Self storage properties, net $ 1,803,992 $ 1,835,235 Other assets 26,094 22,413 Total assets $ 1,830,086 $ 1,857,648 LIABILITIES AND EQUITY Debt financing $ 989,819 $ 989,182 Other liabilities 23,462 20,487 Equity 816,805 847,979 Total liabilities and equity $ 1,830,086 $ 1,857,648 The following tables present the combined condensed operating information of the Company's unconsolidated real estate ventures for the three and nine months ended September 30, 2020 and 2019 (in thousands): Three Months Ended September 30, 2020 2019 Total revenue $ 41,878 $ 41,600 Property operating expenses 13,005 12,727 Net operating income 28,873 28,873 Supervisory, administrative and other expenses (2,780) (2,750) Depreciation and amortization (15,320) (20,788) Interest expense (10,303) (9,934) Acquisition and other expenses (381) (314) Net income (loss) $ 89 $ (4,913) Nine Months Ended September 30, 2020 2019 Total revenue $ 121,846 $ 122,253 Property operating expenses 37,554 37,815 Net operating income 84,292 84,438 Supervisory, administrative and other expenses (8,089) (8,109) Depreciation and amortization (45,711) (64,502) Interest expense (30,867) (29,895) Loss on sale of self storage properties — (806) Acquisition and other expenses (800) (1,141) Net loss $ (1,175) $ (20,015)

ACQUISITIONS (Tables)

ACQUISITIONS (Tables)	9 Months Ended
	Sep. 30, 2020
Asset Acquisitions And Dispositions [Abstract]
Schedule of investment in self storage property acquisitions	The following table summarizes the investment in self storage property acquisitions completed by the Company during the nine months ended September 30, 2020 (dollars in thousands): Acquisitions Closed During the Three Months Ended: Number of Properties Summary of Investment Cash and Acquisition Costs Value of OP Equity (1) Other Liabilities Total March 31, 2020 36 $ 214,584 $ 7,217 $ 972 $ 222,773 June 30, 2020 4 30,198 5,842 207 36,247 September 30, 2020 4 20,173 3,427 204 23,804 Total 44 $ 264,955 $ 16,486 $ 1,383 $ 282,824 (1) Value of OP equity represents the fair value of LTIP units, OP units and subordinated performance units.

OTHER ASSETS (Tables)

OTHER ASSETS (Tables)	9 Months Ended
	Sep. 30, 2020
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Schedule of other assets	Other assets consist of the following (dollars in thousands): September 30, 2020 December 31, 2019 Customer in-place leases, net of accumulated amortization of $4,156 and $7,267, respectively $ 2,694 $ 3,704 Receivables: Trade, net 2,479 2,809 PROs and other affiliates 2,641 2,773 Receivables from unconsolidated real estate ventures 5,154 4,765 Property acquisition and other deposits 550 4,438 Interest rate swaps — 980 Equity securities — 7,703 Prepaid expenses and other 6,320 4,762 Corporate furniture, equipment and other, net 1,825 1,925 Trade names 6,380 3,200 Management contracts, net of accumulated amortization of $2,969 and $2,274, respectively 12,251 8,349 Tenant reinsurance intangible, net of accumulated amortization of $756 and $317, respectively 13,844 14,283 Goodwill 8,182 5,750 Total $ 62,320 $ 65,441

DEBT FINANCING (Tables)

DEBT FINANCING (Tables)	9 Months Ended
	Sep. 30, 2020
Debt Disclosure [Abstract]
Schedule of debt	The Company's outstanding debt as of September 30, 2020 and December 31, 2019 is summarized as follows (dollars in thousands): Interest Rate (1) September 30, 2020 December 31, 2019 Credit Facility: Revolving line of credit 1.45% $ 246,500 $ — Term loan A 3.74% 125,000 125,000 Term loan B 2.91% 250,000 250,000 Term loan C 2.80% 225,000 225,000 Term loan D 3.57% 175,000 175,000 2023 Term loan facility 2.83% 175,000 175,000 2028 Term loan facility 4.62% 75,000 75,000 2029 Term loan facility 4.27% 100,000 100,000 2029 Senior Unsecured Notes 3.98% 100,000 100,000 2031 Senior Unsecured Notes 4.08% 50,000 50,000 Fixed rate mortgages payable 4.26% 224,653 264,260 Total principal 1,746,153 1,539,260 Unamortized debt issuance costs and debt premium, net (4,450) (5,213) Total debt $ 1,741,703 $ 1,534,047 (1) Represents the effective interest rate as of September 30, 2020. Effective interest rate incorporates the stated rate plus the impact of interest rate cash flow hedges and discount and premium amortization, if applicable. For the revolving line of credit, the effective interest rate excludes fees for unused borrowings.
Schedule of future debt maturities	Based on existing debt agreements in effect as of September 30, 2020, the scheduled principal and maturity payments for the Company's outstanding borrowings are presented in the table below (in thousands): Year Ending December 31, Scheduled Principal and Maturity Payments Amortization of Premium and Unamortized Debt Issuance Costs Total Remainder of 2020 $ 1,040 $ (381) $ 659 2021 7,603 (1,522) 6,081 2022 4,205 (1,512) 2,693 2023 377,049 (1,159) 375,890 2024 518,464 (790) 517,674 2025 227,185 (218) 226,967 Thereafter 610,607 1,132 611,739 $ 1,746,153 $ (4,450) $ 1,741,703

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Schedule of the computation of basic and diluted earnings per common share	The following table sets forth the computation of basic and diluted earnings (loss) per common share for the three and nine months ended September 30, 2020 and 2019 (in thousands, except per share amounts): Three Months Ended Nine Months Ended 2020 2019 2020 2019 Earnings (loss) per common share - basic and diluted Numerator Net income $ 21,411 $ 16,514 $ 54,961 $ 47,187 Net income attributable to noncontrolling interests (7,924) (25,374) (24,404) (56,292) Net income (loss) attributable to National Storage Affiliates Trust 13,487 (8,860) 30,557 (9,105) Distributions to preferred shareholders (3,275) (3,272) (9,822) (9,117) Distributed and undistributed earnings allocated to participating securities (11) (8) (34) (26) Net income (loss) attributable to common shareholders - basic and diluted $ 10,201 $ (12,140) $ 20,701 $ (18,248) Denominator Weighted average shares outstanding - basic and diluted 68,887 59,278 65,643 57,835 Earnings (loss) per share - basic and diluted $ 0.15 $ (0.20) $ 0.32 $ (0.32)

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Schedule of interest rate swap derivatives measured at fair value	Information regarding the Company's interest rate swaps measured at fair value, which are classified within Level 2 of the GAAP fair value hierarchy, is presented below (dollars in thousands): Fair value at December 31, 2018 $ 14,195 Gains on interest rate swaps reclassified into interest expense from accumulated other comprehensive (loss) income (3,492) Unrealized losses on interest rate swaps included in accumulated other comprehensive (loss) income (44,547) Fair value at September 30, 2019 $ (33,844) Fair value at December 31, 2019 $ (19,083) Losses on interest rate swaps reclassified into interest expense from accumulated other comprehensive (loss) income 9,519 Unrealized losses on interest rate swaps included in accumulated other comprehensive (loss) income (77,354) Fair value at September 30, 2020 $ (86,918)

LEASES (Tables)

LEASES (Tables)	9 Months Ended
	Sep. 30, 2020
Leases [Abstract]
Schedule of weighted-average remaining lease terms and weighted-average discount rates	The weighted-average remaining lease term and the weighted-average discount rate for the Company's operating leases as of September 30, 2020 are as follows: September 30, 2020 Weighted-average remaining lease term Real estate leasehold interests 28 years Office leases 7 years Weighted-average remaining discount rate Real estate leasehold interests 4.9 % Office leases 3.8 %
Schedule of future minimum lease payments	As of September 30, 2020, the future minimum lease payments under the Company's operating leases, for which the Company is a lessee, are as follows (in thousands): Year Ending December 31, Real Estate Leasehold Interests Office Leases Total Remainder of 2020 $ 357 $ 106 $ 463 2021 1,444 471 1,915 2022 1,459 465 1,924 2023 1,464 430 1,894 2024 1,470 450 1,920 2025 through 2092 36,728 1,080 37,808 Total lease payments $ 42,922 $ 3,002 $ 45,924 Less imputed interest (20,640) (355) (20,995) Total $ 22,282 $ 2,647 $ 24,929 As of December 31, 2019, the future minimum lease payments under the Company's operating leases, for which the Company is a lessee, are as follows (in thousands): Year Ending December 31, Real Estate Leasehold Interests Office Leases Total 2020 $ 1,419 $ 286 $ 1,705 2021 1,444 387 1,831 2022 1,459 381 1,840 2023 1,464 346 1,810 2024 1,470 353 1,823 2025 through 2092 36,728 691 37,419 Total lease payments $ 43,984 $ 2,444 $ 46,428 Less imputed interest (21,440) (323) (21,763) Total $ 22,544 $ 2,121 $ 24,665

ORGANIZATION AND NATURE OF OP_2

ORGANIZATION AND NATURE OF OPERATIONS (Details) storage_unit in Thousands, ft² in Millions	9 Months Ended
	Sep. 30, 2020ft²metropolitan_statistical_areastorage_unitstateproperty	Dec. 31, 2016property
Schedule of Equity Method Investments [Line Items]
Number of top metropolitan statistical areas for focus of operations | metropolitan_statistical_area	100
Number of self storage properties | property	788
Number of states in which self storage properties are located | state	35
Total rentable square feet in self storage properties | ft²	49.5
Number of storage units | storage_unit	396
2016 Joint Venture
Schedule of Equity Method Investments [Line Items]
Company's equity interest in unconsolidated real estate ventures (percent)	25.00%
2016 Joint Venture | Joint venture
Schedule of Equity Method Investments [Line Items]
Company's equity interest in unconsolidated real estate ventures (percent)	25.00%
2018 Joint Venture
Schedule of Equity Method Investments [Line Items]
Company's equity interest in unconsolidated real estate ventures (percent)	25.00%
2018 Joint Venture | Joint venture
Schedule of Equity Method Investments [Line Items]
Company's equity interest in unconsolidated real estate ventures (percent)	25.00%
Consolidated properties
Schedule of Equity Method Investments [Line Items]
Number of self storage properties | property	611
Number of states in which self storage properties are located | state	29
Total rentable square feet in self storage properties | ft²	36.8
Number of storage units | storage_unit	293
Unconsolidated properties | Unconsolidated real estate ventures | Joint venture
Schedule of Equity Method Investments [Line Items]
Number of self storage properties | property	177
Number of states in which self storage properties are located | state	21
Total rentable square feet in self storage properties | ft²	12.7
Number of storage units | storage_unit	103
Unconsolidated properties | 2016 Joint Venture | Joint venture
Schedule of Equity Method Investments [Line Items]
Number of self storage properties | property	74	66
Number of states in which self storage properties are located | state	13
Total rentable square feet in self storage properties | ft²	4.9
Number of storage units | storage_unit	40
Unconsolidated properties | 2018 Joint Venture | Joint venture
Schedule of Equity Method Investments [Line Items]
Number of self storage properties | property	103
Number of states in which self storage properties are located | state	17
Total rentable square feet in self storage properties | ft²	7.8
Number of storage units | storage_unit	63

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) $ in Thousands	Sep. 30, 2020USD ($)propertypartnership	Dec. 31, 2019USD ($)propertypartnership
Variable Interest Entity [Line Items]
Number of self storage properties | property	788
Net book value of real estate owned	$ 2,964,995	$ 2,753,897
Carrying value of fixed rate mortgages	1,746,153	1,539,260
Fixed rate mortgages payable | Fixed rate mortgages payable
Variable Interest Entity [Line Items]
Carrying value of fixed rate mortgages	$ 224,653	$ 264,260
VIE, Primary Beneficiary
Variable Interest Entity [Line Items]
Number of partnerships considered to be VIEs | partnership	21	21
Number of self storage properties | property	34	34
Net book value of real estate owned	$ 227,200	$ 233,100
VIE, Primary Beneficiary | Fixed rate mortgages payable | Fixed rate mortgages payable
Variable Interest Entity [Line Items]
Carrying value of fixed rate mortgages	$ 100,700	$ 136,400

SUMMARY OF SIGNIFICANT ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenue Recognition (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020USD ($)property	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)property	Sep. 30, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2016USD ($)property	Dec. 31, 2019USD ($)
Disaggregation of Revenue [Line Items]
Number of self storage properties | property	788		788
Initial term of unconsolidated real estate venture agreements			4 years
Performance obligation period of recognition			4 years
Joint venture | 2016 Joint Venture | Unconsolidated properties
Disaggregation of Revenue [Line Items]
Number of self storage properties | property	74		74			66
Tenant Insurance and Tenant Warranty Protection Plan Revenues
Disaggregation of Revenue [Line Items]
Revenue	$ 2,900,000	$ 2,400,000	$ 8,200,000	$ 6,700,000
Retail Products and Supplies
Disaggregation of Revenue [Line Items]
Revenue	600,000	400,000	1,400,000	1,300,000
Property Management, Call Center, and Platform Fees
Disaggregation of Revenue [Line Items]
Revenue	3,400,000	3,300,000	$ 9,800,000	9,700,000
Property management fees as percent of monthly gross revenues and net sales revenue of unconsolidated real estate venture assets			6.00%
Platform fees per unconsolidated real estate venture property per month			$ 1,250
Call center fees as percent of monthly gross revenues and net sales revenue of unconsolidated real estate venture assets			1.00%
Acquisition Fees
Disaggregation of Revenue [Line Items]
Revenue	500,000	400,000	$ 1,400,000	1,400,000
Acquisition fee					$ 4,000,000	$ 4,100,000
Acquisition fees received as a percent of gross capitalization of Initial 2016 JV Portfolio						0.65%
Deferred revenue related to acquisition fees	1,400,000		1,400,000				$ 2,800,000
Tenant Warranty Protection or Tenant Insurance
Disaggregation of Revenue [Line Items]
Revenue	$ 2,000,000	$ 1,200,000	$ 5,500,000	$ 3,600,000
Percent of total warranty protection plan proceeds received per unconsolidated real estate venture property			50.00%

SHAREHOLDERS' EQUITY AND NONC_3

SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS - Narrative (Details) - USD ($)	Oct. 06, 2020	Sep. 30, 2020	Sep. 22, 2020	Feb. 27, 2019	Oct. 06, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Class of Stock [Line Items]
Common shares of beneficial interest, par value (in dollars per share)		$ 0.01		$ 0.01		$ 0.01						$ 0.01		$ 0.01
Value of common and preferred shares authorized under ATM program				$ 250,000,000
Preferred share/unit dividend rate (percent)				6.00%
Proceeds from issuance of common shares												$ 22,033,000	$ 70,637,000
Preferred units stated value (in dollars per share)		$ 0.01				$ 0.01						$ 0.01		0.01
Common Shares
Class of Stock [Line Items]
Issuance of shares/units (in shares)										2,375,000
Redemptions/conversions of units (in shares)							292,291	118,961	32,951	224,618	29,910
Contribution of units arising from the mergers (in shares)								8,105,192
Arlen Nordhagen | SecurCare
Class of Stock [Line Items]
Related party ownership interest		53.00%				53.00%						53.00%
David Cramer | SecurCare
Class of Stock [Line Items]
Related party ownership interest		24.00%				24.00%						24.00%
SecurCare and DLAN
Class of Stock [Line Items]
Number common shares issued upon conversion (in shares)		8,105,192				8,105,192						8,105,192
Discount rate on conversion		1.00%				1.00%						1.00%
SecurCare and DLAN | Arlen Nordhagen
Class of Stock [Line Items]
Number common shares issued upon conversion (in shares)		4,063,571				4,063,571						4,063,571
SecurCare and DLAN | David Cramer
Class of Stock [Line Items]
Number common shares issued upon conversion (in shares)		1,858,737				1,858,737						1,858,737
Series A-1 Preferred Units | NSA OP, LP
Class of Stock [Line Items]
Preferred share/unit dividend rate (percent)												6.00%
Preferred units stated value (in dollars per share)		$ 25				$ 25						$ 25
Unit conversion ratio												1
Redemptions/conversions of units (in shares)						5,600
OP units | SecurCare and DLAN
Class of Stock [Line Items]
Number of units to own/receive (in shares)		8,187,052				8,187,052						8,187,052
OP units | NSA OP, LP
Class of Stock [Line Items]
Issuance of shares/units (in shares)												445,701
Unit conversion ratio												1
Minimum conversion period (in years)												1 year
Conversion of units (in shares)												368,500
Units retired during the period (in shares)												710,462
OP units | NSA OP, LP | Common Shares
Class of Stock [Line Items]
Redemptions/conversions of units (in shares)												704,335
OP units | NSA OP, LP | Self Storage Properties
Class of Stock [Line Items]
Issuance of shares/units (in shares)												378,239
OP units | DownREIT Partnership
Class of Stock [Line Items]
Issuance of shares/units (in shares)												115,888
Unit conversion ratio												1
Minimum conversion period (in years)												5 years
Conversion of units (in shares)												368,500
Contribution of units arising from the mergers (in shares)												407,731
Subordinated performance units
Class of Stock [Line Items]
Time frame prior to conversion for conversion metric (in years)												1 year
Percentage of cash available for distribution used in conversion ratio calculation												110.00%
Subordinated performance units | NSA OP, LP
Class of Stock [Line Items]
Redemptions/conversions of units (in shares)												332,738
Unit conversion, lock out period (in years)												2 years
Units retired during the period (in shares)												2,001,441
Subordinated performance units | NSA OP, LP | Self Storage Properties
Class of Stock [Line Items]
Issuance of shares/units (in shares)												90,728
Subordinated performance units | DownREIT Partnership
Class of Stock [Line Items]
Unit conversion ratio												1
Minimum conversion period (in years)												5 years
Redemptions/conversions of units (in shares)												34,511
LTIP units | NSA OP, LP
Class of Stock [Line Items]
Issuance of shares/units (in shares)												236,786
Unit conversion ratio												1
Conversion of units (in shares)												214,512
Common shares | Common Shares
Class of Stock [Line Items]
Issuance of shares/units (in shares)						181,915	387,000	125,000
Redemptions/conversions of units (in shares)						293,083
Common shares | At the Market Program
Class of Stock [Line Items]
Issuance of shares/units (in shares)												693,915
Average offering price (in dollars per share)		$ 32.92				$ 32.92						$ 32.92
Proceeds from issuance of common shares												$ 22,000,000
Common shares | Public Stock Offering
Class of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)			4,500,000
Sale of stock, price per share (in dollars per share)			$ 33.15
Common shares | Public Stock Offering | Subsequent Event
Class of Stock [Line Items]
Sale of stock, additional number of shares issued in transaction (in shares)	400,000
Common shares | Public Stock Offering - From Third Parties
Class of Stock [Line Items]
Sale of stock, price per share (in dollars per share)		$ 32.832				$ 32.832						$ 32.832
Sale of stock, consideration received on transaction		$ 160,000,000
Common shares | Public Stock Offering - From Third Parties | Subsequent Event
Class of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)					4,900,000
Sale of stock, price per share (in dollars per share)	$ 33.15				$ 33.15
Sale of stock, consideration received on transaction					$ 162,400,000
Series A preferred shares | NSA OP, LP
Class of Stock [Line Items]
Preferred units cash redemption price (in dollars per share)														$ 25
Over-Allotment Option | Public Stock Offering
Class of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)			675,000

SHAREHOLDERS' EQUITY AND NONC_4

SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS - Equity Interests (Details) - shares	Sep. 30, 2020	Dec. 31, 2019
Partnership Subsidiaries
Noncontrolling Interest [Line Items]
Outstanding equity interest (in shares)	45,879,455	48,808,931
Series A-1 Preferred Units | NSA OP, LP
Noncontrolling Interest [Line Items]
Outstanding equity interest (in shares)	637,382	642,982
OP units | NSA OP, LP
Noncontrolling Interest [Line Items]
Outstanding equity interest (in shares)	29,443,460	30,188,305
OP units | DownREIT Partnership
Noncontrolling Interest [Line Items]
Outstanding equity interest (in shares)	1,924,918	1,848,261
Subordinated performance units | NSA OP, LP
Noncontrolling Interest [Line Items]
Outstanding equity interest (in shares)	8,770,744	11,014,195
Subordinated performance units | DownREIT Partnership
Noncontrolling Interest [Line Items]
Outstanding equity interest (in shares)	4,337,111	4,371,622
LTIP units | NSA OP, LP
Noncontrolling Interest [Line Items]
Outstanding equity interest (in shares)	765,840	743,566

SELF STORAGE PROPERTIES (Detail

SELF STORAGE PROPERTIES (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Real Estate [Abstract]
Land	$ 690,581		$ 690,581		$ 649,938
Buildings and improvements	2,683,288		2,683,288		2,435,171
Furniture and equipment	7,549		7,549		6,610
Total self storage properties	3,381,418		3,381,418		3,091,719
Less accumulated depreciation	(416,423)		(416,423)		(337,822)
Self storage properties, net	2,964,995		2,964,995		$ 2,753,897
Depreciation expense related to self storage properties	$ 26,600	$ 23,800	$ 78,600	$ 68,000

INVESTMENT IN UNCONSOLIDATED _3

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Narrative (Details) storage_unit in Thousands, $ in Thousands, ft² in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2020ft²storage_unitpropertystate	Jun. 30, 2020property	Mar. 31, 2020property	Sep. 30, 2020USD ($)ft²propertystorage_unitstate	Sep. 30, 2019USD ($)	Dec. 31, 2016property
Schedule of Equity Method Investments [Line Items]
Number of self storage properties	788			788
Rentable square feet in self storage properties | ft²	49.5			49.5
Number of storage units | storage_unit	396			396
Number of states in which self storage properties are located | state	35			35
Number of properties acquired	4	4	36	44
Payments to joint venture | $				$ 3,125	$ 0
2018 Joint Venture
Schedule of Equity Method Investments [Line Items]
Company's equity interest in unconsolidated real estate ventures (percent)	25.00%			25.00%
2016 Joint Venture
Schedule of Equity Method Investments [Line Items]
Company's equity interest in unconsolidated real estate ventures (percent)	25.00%			25.00%
Joint venture | 2018 Joint Venture
Schedule of Equity Method Investments [Line Items]
Company's equity interest in unconsolidated real estate ventures (percent)	25.00%			25.00%
Joint venture | 2016 Joint Venture
Schedule of Equity Method Investments [Line Items]
Payments to joint venture | $				$ 3,100
Company's equity interest in unconsolidated real estate ventures (percent)	25.00%			25.00%
Unconsolidated properties | Joint venture | 2018 Joint Venture
Schedule of Equity Method Investments [Line Items]
Number of self storage properties	103			103
Rentable square feet in self storage properties | ft²	7.8			7.8
Number of storage units | storage_unit	63			63
Number of states in which self storage properties are located | state	17			17
Unconsolidated properties | Joint venture | 2016 Joint Venture
Schedule of Equity Method Investments [Line Items]
Number of self storage properties	74			74		66
Rentable square feet in self storage properties | ft²	4.9			4.9
Number of storage units | storage_unit	40			40
Number of states in which self storage properties are located | state	13			13
Number of properties acquired				2
Payments to acquire property | $				$ 12,100

INVESTMENT IN UNCONSOLIDATED _4

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Condensed Financial Position (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
ASSETS
Self storage properties, net	$ 2,964,995			$ 2,753,897
Other assets	62,320			65,441
Total assets	3,280,916			3,084,245
LIABILITIES AND EQUITY
Debt financing	1,741,703			1,534,047
Equity	1,360,400	$ 1,368,745	$ 1,381,055	1,452,101	$ 1,457,206	$ 1,498,784	$ 1,403,188	$ 1,402,299
Total liabilities and equity	3,280,916			3,084,245
Joint venture | Unconsolidated real estate ventures
ASSETS
Self storage properties, net	1,803,992			1,835,235
Other assets	26,094			22,413
Total assets	1,830,086			1,857,648
LIABILITIES AND EQUITY
Debt financing	989,819			989,182
Other liabilities	23,462			20,487
Equity	816,805			847,979
Total liabilities and equity	$ 1,830,086			$ 1,857,648

INVESTMENT IN UNCONSOLIDATED _5

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Condensed Operating Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Related Party Transaction [Line Items]
Total revenue	$ 109,474	$ 101,337	$ 318,113	$ 287,328
Property operating expenses	31,546	28,988	92,395	82,635
Depreciation and amortization	(28,933)	(27,598)	(87,347)	(77,776)
Interest expense	(15,262)	(14,432)	(46,403)	(41,590)
Acquisition costs	(596)	(321)	(1,681)	(783)
Net income (loss)	13,487	(8,860)	30,557	(9,105)
Joint venture | Unconsolidated real estate ventures
Related Party Transaction [Line Items]
Total revenue	41,878	41,600	121,846	122,253
Property operating expenses	13,005	12,727	37,554	37,815
Net operating income	28,873	28,873	84,292	84,438
Supervisory, administrative and other expenses	(2,780)	(2,750)	(8,089)	(8,109)
Depreciation and amortization	(15,320)	(20,788)	(45,711)	(64,502)
Interest expense	(10,303)	(9,934)	(30,867)	(29,895)
Loss on sale of self storage properties			0	(806)
Acquisition costs	(381)	(314)	(800)	(1,141)
Net income (loss)	$ 89	$ (4,913)	$ (1,175)	$ (20,015)

ACQUISITIONS - Narrative (Detai

ACQUISITIONS - Narrative (Details) $ in Thousands	Mar. 31, 2020USD ($)shares	Sep. 30, 2020USD ($)property	Jun. 30, 2020property	Mar. 31, 2020USD ($)propertyshares	Sep. 30, 2020USD ($)property	Dec. 31, 2019USD ($)
Schedule of Asset Acquisition [Line Items]
Number of properties acquired | property		4	4	36	44
Estimated fair value of net assets acquired					$ 282,800
Acquisition-related costs capitalized					3,300
Goodwill		$ 8,182			8,182	$ 5,750
SecurCare and DLAN
Schedule of Asset Acquisition [Line Items]
Amount allocated to tangible fixed assets	$ 100			$ 100
Goodwill	2,400			2,400
SecurCare and DLAN | Trade name
Schedule of Asset Acquisition [Line Items]
Amount allocated to indefinite lived intangible assets	$ 3,200			$ 3,200
SecurCare | OP units
Schedule of Asset Acquisition [Line Items]
Number of units to be issued for internalization transaction (in shares) | shares	348,020			348,020
SecurCare | OP units | SecurCare and DLAN
Schedule of Asset Acquisition [Line Items]
Value of OP units issued in acquisition	$ 10,300
Real estate
Schedule of Asset Acquisition [Line Items]
Recognized fair value allocated to real estate					276,800
Customer in-place leases
Schedule of Asset Acquisition [Line Items]
Recognized fair value allocated to intangible assets					$ 6,000
Management contract
Schedule of Asset Acquisition [Line Items]
Finite lived intangibles, useful life	15 years
Management contract | SecurCare and DLAN
Schedule of Asset Acquisition [Line Items]
Amount allocated to finite lived intangible assets	$ 4,600			$ 4,600
Assets acquired from PROs | Affiliated entity
Schedule of Asset Acquisition [Line Items]
Number of properties acquired | property					5
Estimated fair value of net assets acquired					$ 44,300

ACQUISITIONS - Summary of Acqui

ACQUISITIONS - Summary of Acquisitions (Details) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2020USD ($)property	Jun. 30, 2020USD ($)property	Mar. 31, 2020USD ($)property	Sep. 30, 2020USD ($)property
Asset Acquisitions During Period
Number of Properties | property	4	4	36	44
Cash and Acquisition Costs	$ 20,173	$ 30,198	$ 214,584	$ 264,955
Value of OP Equity	3,427	5,842	7,217	16,486
Other Liabilities	204	207	972	1,383
Total	$ 23,804	$ 36,247	$ 222,773	$ 282,824

OTHER ASSETS - Schedule of Othe

OTHER ASSETS - Schedule of Other Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Receivables:
Trade, net	$ 2,479	$ 2,809
PROs and other affiliates	2,641	2,773
Receivables from unconsolidated real estate ventures	5,154	4,765
Property acquisition and other deposits	550	4,438
Interest rate swaps	0	980
Equity securities	0	7,703
Prepaid expenses and other	6,320	4,762
Corporate furniture, equipment and other, net	1,825	1,925
Goodwill	8,182	5,750
Total	62,320	65,441
Customer in-place leases
Other Assets
Intangibles	2,694	3,704
Accumulated amortization	4,156	7,267
Management contract
Other Assets
Intangibles	12,251	8,349
Accumulated amortization	2,969	2,274
Tenant reinsurance intangible
Other Assets
Intangibles	13,844	14,283
Accumulated amortization	756	317
Trade name
Receivables:
Trade names	$ 6,380	$ 3,200

OTHER ASSETS - Narrative (Detai

OTHER ASSETS - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Customer in-place leases
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 1.7	$ 3.3	$ 7	$ 8.6
Management contract
Finite-Lived Intangible Assets [Line Items]
Amortization expense	0.2	0.2	0.7	0.6
Tenant reinsurance intangible
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 0.1	$ 0.2	$ 0.3	$ 0.2

DEBT FINANCING - Debt Summary (

DEBT FINANCING - Debt Summary (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Principal amount	$ 1,746,153	$ 1,539,260
Unamortized debt issuance costs and debt premium, net	(4,450)	(5,213)
Total debt	$ 1,741,703	1,534,047
Revolving line of credit | Credit Facility | Revolving line of credit
Debt Instrument [Line Items]
Effective interest rate (percent)	1.45%
Principal amount	$ 246,500	0
Unsecured debt | Credit Facility | Term loan A
Debt Instrument [Line Items]
Effective interest rate (percent)	3.74%
Principal amount	$ 125,000	125,000
Unsecured debt | Credit Facility | Term loan B
Debt Instrument [Line Items]
Effective interest rate (percent)	2.91%
Principal amount	$ 250,000	250,000
Unsecured debt | Credit Facility | Term loan C
Debt Instrument [Line Items]
Effective interest rate (percent)	2.80%
Principal amount	$ 225,000	225,000
Unsecured debt | Credit Facility | Term loan D
Debt Instrument [Line Items]
Effective interest rate (percent)	3.57%
Principal amount	$ 175,000	175,000
Unsecured debt | 2023 Term loan facility
Debt Instrument [Line Items]
Effective interest rate (percent)	2.83%
Principal amount	$ 175,000	175,000
Unsecured debt | 2028 Term loan facility
Debt Instrument [Line Items]
Effective interest rate (percent)	4.62%
Principal amount	$ 75,000	75,000
Unsecured debt | 2029 Term loan facility
Debt Instrument [Line Items]
Effective interest rate (percent)	4.27%
Principal amount	$ 100,000	100,000
Unsecured debt | 2029 Senior Unsecured Notes
Debt Instrument [Line Items]
Effective interest rate (percent)	3.98%
Principal amount	$ 100,000	100,000
Unsecured debt | 2031 Senior Unsecured Notes
Debt Instrument [Line Items]
Effective interest rate (percent)	4.08%
Principal amount	$ 50,000	50,000
Fixed rate mortgages payable | Fixed rate mortgages payable
Debt Instrument [Line Items]
Effective interest rate (percent)	4.26%
Principal amount	$ 224,653	$ 264,260

DEBT FINANCING - Narrative (Det

DEBT FINANCING - Narrative (Details) - USD ($)	Oct. 22, 2020	Sep. 30, 2020
Unsecured debt | Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 1,275,000,000
Maximum borrowing capacity if expansion option is exercised		1,750,000,000
Unsecured debt | 2030 Notes | Subsequent Event
Debt Instrument [Line Items]
Debt instrument, face amount	$ 150,000,000
Debt instrument, interest rate (percent)	2.99%
Unsecured debt | 2032 Notes | Subsequent Event
Debt Instrument [Line Items]
Debt instrument, face amount	$ 100,000,000
Debt instrument, interest rate (percent)	3.09%
Revolving line of credit | Revolving line of credit | Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity		500,000,000
Revolving line of credit remaining borrowing capacity		247,800,000
Term loan A | Unsecured debt | Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity		125,000,000
Term loan B | Unsecured debt | Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity		250,000,000
Term loan C | Unsecured debt | Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity		225,000,000
Term loan D | Unsecured debt | Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity		175,000,000
Letter of credit | Revolving line of credit | Credit Facility
Debt Instrument [Line Items]
Letters of credit outstanding		$ 5,700,000

DEBT FINANCING - Future Debt Ob

DEBT FINANCING - Future Debt Obligations (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Scheduled Principal and Maturity Payments
Remainder of 2020	$ 1,040
2021	7,603
2022	4,205
2023	377,049
2024	518,464
2025	227,185
Thereafter	610,607
Total principal	1,746,153	$ 1,539,260
Amortization of Premium and Unamortized Debt Issuance Costs
Remainder of 2020	(381)
2021	(1,522)
2022	(1,512)
2023	(1,159)
2024	(790)
2025	(218)
Thereafter	1,132
Total unamortized debt issuance costs and debt premium, net	(4,450)	(5,213)
Total
Remainder of 2020	659
2021	6,081
2022	2,693
2023	375,890
2024	517,674
2025	226,967
Thereafter	611,739
Total debt	$ 1,741,703	$ 1,534,047

EARNINGS PER SHARE - Basic and

EARNINGS PER SHARE - Basic and Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator
Net income	$ 21,411	$ 17,787	$ 15,763	$ 16,514	$ 17,733	$ 12,940	$ 54,961	$ 47,187
Net income attributable to noncontrolling interests	(7,924)			(25,374)			(24,404)	(56,292)
Net income (loss) attributable to National Storage Affiliates Trust	13,487			(8,860)			30,557	(9,105)
Distributions to preferred shareholders	(3,275)			(3,272)			(9,822)	(9,117)
Distributed and undistributed earnings allocated to participating securities	(11)			(8)			(34)	(26)
Net income (loss) attributable to common shareholders - basic and diluted	$ 10,201			$ (12,140)			$ 20,701	$ (18,248)
Denominator
Weighted average shares outstanding - basic and diluted (in shares)	68,887			59,278			65,643	57,835
Earnings (loss) per share - basic and diluted (in dollars per share)	$ 0.15			$ (0.20)			$ 0.32	$ (0.32)

EARNINGS PER SHARE - Narrative

EARNINGS PER SHARE - Narrative (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2020shares	Sep. 30, 2019shares	Sep. 30, 2020shares	Sep. 30, 2019shares
NSA OP, LP | OP units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Unit conversion ratio			1
Minimum conversion period (in years)			1 year
NSA OP, LP | LTIP units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Unit conversion ratio			1
DownREIT Partnership | OP units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Unit conversion ratio			1
Minimum conversion period (in years)			5 years
DownREIT Partnership | Subordinated performance units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Unit conversion ratio			1
Minimum conversion period (in years)			5 years
NSA OP, LP And DownREIT Partnership | Subordinated performance units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Unit conversion ratio			1
Minimum conversion period (in years)			2 years
LTIP units with vesting based on service or market condition
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Equity interests excluded from computation of diluted earnings per share (in shares)	420,280		420,280
LTIP units with vesting based on future acquisitions
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Equity interests excluded from computation of diluted earnings per share (in shares)	252,894		252,894
OP units, DownREIT OP units, Subordinated performance units, DownREIT subordinated performance units, Vested LTIP units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Equity interests excluded from computation of diluted earnings per share (in shares)	47,000,000	55,200,000	48,300,000	53,900,000

RELATED PARTY TRANSACTIONS (Det

RELATED PARTY TRANSACTIONS (Details) $ in Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2020USD ($)property	Jun. 30, 2020USD ($)property	Mar. 31, 2020USD ($)property	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)propertyshares	Sep. 30, 2019USD ($)
Related Party Transaction [Line Items]
Payroll and related costs reimbursed to the PROs by the Company	$ 31,546			$ 28,988	$ 92,395	$ 82,635
Number of properties acquired | property	4	4	36		44
Consideration in acquisition transaction	$ 23,804	$ 36,247	$ 222,773		$ 282,824
Value of OP Equity	3,427	$ 5,842	$ 7,217		16,486
Supervisory and Administrative Fee Agreement | Management | Participating Regional Operator (PRO)
Related Party Transaction [Line Items]
Supervisory and administrative fees paid to the PROs	3,700			5,200	$ 12,500	14,800
Supervisory and Administrative Fee Agreement | Management | Participating Regional Operator (PRO) | Minimum
Related Party Transaction [Line Items]
Supervisory and administrative fee agreement of gross revenue, percent					5.00%
Supervisory and Administrative Fee Agreement | Management | Participating Regional Operator (PRO) | Maximum
Related Party Transaction [Line Items]
Supervisory and administrative fee agreement of gross revenue, percent					6.00%
Payroll Services | Management | Participating Regional Operator (PRO)
Related Party Transaction [Line Items]
Payroll and related costs reimbursed to the PROs by the Company	$ 5,700			8,100	$ 20,000	23,800
Due Diligence Costs | Management | Participating Regional Operator (PRO)
Related Party Transaction [Line Items]
Due diligence expenses payable to the PROs				$ 100	$ 200	$ 700
Self storage property purchase from affiliate of executives | Affiliated entity
Related Party Transaction [Line Items]
Number of properties acquired | property					1
Consideration in acquisition transaction					$ 7,500
Self storage property purchase from affiliate of trustee | Affiliated entity
Related Party Transaction [Line Items]
Number of properties acquired | property					1
Consideration in acquisition transaction					$ 6,600
OP units | Self storage property purchase from affiliate of executives | Affiliated entity | Mr. Arlen Nordhagen
Related Party Transaction [Line Items]
Number of OP Units in acquisition (in shares) | shares					58,376
Value of OP Equity					$ 1,500
OP units | Self storage property purchase from affiliate of executives | Affiliated entity | Mr. David Cramer
Related Party Transaction [Line Items]
Number of OP Units in acquisition (in shares) | shares					29,689
Value of OP Equity					$ 700
OP units | Self storage property purchase from affiliate of trustee | Affiliated entity | Mr. J. Timothy Warren
Related Party Transaction [Line Items]
Number of OP Units in acquisition (in shares) | shares					15,512
Value of OP Equity					$ 400

FAIR VALUE MEASUREMENTS - Inter

FAIR VALUE MEASUREMENTS - Interest Swap Derivatives (Details) - Interest Rate Swap - Level 2 - Designated as Hedging Instrument - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis [Roll Forward]
Fair value at beginning of period	$ (19,083)	$ 14,195
Gains on interest rate swaps reclassified into interest expense from accumulated other comprehensive (loss) income	9,519	(3,492)
Unrealized losses on interest rate swaps included in accumulated other comprehensive (loss) income	(77,354)	(44,547)
Fair value of end of period	$ (86,918)	$ (33,844)

FAIR VALUE MEASUREMENTS - Narra

FAIR VALUE MEASUREMENTS - Narrative (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net	$ 20,000,000
Level 2 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed rate mortgages, fair value disclosure	$ 252,900,000	$ 280,900,000
Weighted average market interest rate (percent)	2.06%	3.28%
Weighted average contractual interest rate (percent)	4.69%	4.81%
Reported Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed rate mortgages, fair value disclosure	$ 224,700,000	$ 264,300,000
Designated as Hedging Instrument | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional amount	$ 1,125,000,000	$ 1,125,000,000
Weighted average remaining term	3 years 6 months
Weighted average fixed rate (percent)	1.90%

LEASES - Narrative (Details)

LEASES - Narrative (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)property	Sep. 30, 2019USD ($)
Real estate leasehold interest
Lessee, Lease, Description [Line Items]
Number of properties subject to non-cancelable leasehold interest agreements | property			8
Rent expense	$ 0.4	$ 0.4	$ 1.3	$ 1.2
Real estate leasehold interest | Minimum
Lessee, Lease, Description [Line Items]
Operating leases, term (in years)	14 years		14 years
Real estate leasehold interest | Maximum
Lessee, Lease, Description [Line Items]
Operating leases, term (in years)	72 years		72 years
Office leases
Lessee, Lease, Description [Line Items]
Rent expense	$ 0.1	$ 0.1	$ 0.3	$ 0.2
Office leases | Minimum
Lessee, Lease, Description [Line Items]
Operating leases, term (in years)	2 years		2 years
Office leases | Maximum
Lessee, Lease, Description [Line Items]
Operating leases, term (in years)	8 years		8 years

LEASES - Weighted-Average Remai

LEASES - Weighted-Average Remaining Term and Weighted-Average Discount Rate (Details)	Sep. 30, 2020
Real estate leasehold interest
Lessee, Lease, Description [Line Items]
Weighted-average remaining lease term	28 years
Weighted-average remaining discount rate	4.90%
Office leases
Lessee, Lease, Description [Line Items]
Weighted-average remaining lease term	7 years
Weighted-average remaining discount rate	3.80%

LEASES - Future Minimum Lease P

LEASES - Future Minimum Lease Payments Under Operating Leases (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019
Future Minimum Lease Payments
Remainder of 2020	$ 463
Year One	1,915	$ 1,705
Year Two	1,924	1,831
Year Three	1,894	1,840
Year Four	1,920	1,810
Year Five		1,823
2025 through 2092	37,808
2025 through 2092		37,419
Total lease payments	45,924	46,428
Less imputed interest	(20,995)	(21,763)
Operating lease liabilities	24,929	24,665	$ 24,777
Real estate leasehold interest
Future Minimum Lease Payments
Remainder of 2020	357
Year One	1,444	1,419
Year Two	1,459	1,444
Year Three	1,464	1,459
Year Four	1,470	1,464
Year Five		1,470
2025 through 2092	36,728
2025 through 2092		36,728
Total lease payments	42,922	43,984
Less imputed interest	(20,640)	(21,440)
Operating lease liabilities	22,282	22,544
Office leases
Future Minimum Lease Payments
Remainder of 2020	106
Year One	471	286
Year Two	465	387
Year Three	430	381
Year Four	450	346
Year Five		353
2025 through 2092	1,080
2025 through 2092		691
Total lease payments	3,002	2,444
Less imputed interest	(355)	(323)
Operating lease liabilities	$ 2,647	$ 2,121

SUBSEQUENT EVENTS (Details)

SUBSEQUENT EVENTS (Details) - Subsequent Event - Unsecured debt	Oct. 22, 2020USD ($)
2030 Notes
Subsequent Event [Line Items]
Debt instrument, face amount	$ 150,000,000
Debt instrument, interest rate (percent)	2.99%
2032 Notes
Subsequent Event [Line Items]
Debt instrument, face amount	$ 100,000,000
Debt instrument, interest rate (percent)	3.09%