SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS - Narrative (Details) $ / shares in Units, $ in Thousands				12 Months Ended
	Jul. 01, 2024 shares	Mar. 16, 2023 USD ($) property shares	Mar. 15, 2023 shares	Dec. 31, 2025 USD ($) property $ / shares shares	Dec. 31, 2024 USD ($) $ / shares shares	Dec. 31, 2023 shares	Nov. 19, 2024 USD ($)	Nov. 14, 2024 USD ($)	Jul. 11, 2022 USD ($)	Feb. 27, 2019 USD ($)
Class of Stock [Line Items]
Redemptions of units (in shares)	(11,906,167)
Preferred shares of beneficial interest, outstanding (in shares)				14,704,845	14,695,458
Preferred shares of beneficial interest, authorized (in shares)				50,000,000	50,000,000
Preferred shares of beneficial interest, par value (in dollars per share) | $ / shares				$ 0.01	$ 0.01
Issuance of preferred shares (in shares)	17,984,787
Number of properties | property				1,063
Series A and B Preferred shares of beneficial interest, shares authorized, issued and outstanding at liquidation preference | $				$ 341,130	$ 340,895
Sales agreement under ATM program | $										$ 169,100
Repurchase amount | $					$ 275,000			$ 350,000	$ 400,000
Remaining capacity | $				$ 350,300
Common Shares
Class of Stock [Line Items]
Redemptions of units (in shares)				(735,035)	(1,454,837)	(1,275,854)
Series A Preferred Shares
Class of Stock [Line Items]
Preferred shares of beneficial interest, outstanding (in shares)				9,036,717
Series B Preferred Stock
Class of Stock [Line Items]
Preferred shares of beneficial interest, outstanding (in shares)				5,668,128
Preferred stock, shares tied to promissory note		1,059,683
Series B Preferred Stock | Personal Mini
Class of Stock [Line Items]
Issuance of preferred shares (in shares)		5,668,128
Preferred stock, value, issued | $		$ 139,600
Number of properties | property		15
Financing receivable, after allowance for credit loss | $		$ 26,100
Series A and B Preferred shares of beneficial interest, shares authorized, issued and outstanding at liquidation preference | $		26,100
Proceeds from issuance of preferred stock and preference stock | $		113,100
NSA OP, LP | Series A-1 preferred units
Class of Stock [Line Items]
Preferred stock, dividend rate, percentage				6.00%
Preferred shares cash redemption price (in dollars per share) | $ / shares				$ 25.00
Unit conversion ratio				1
Minimum conversion period (in years)				10 years
NSA OP, LP | Series B Preferred Stock
Class of Stock [Line Items]
Preferred stock, dividend rate, percentage			6.00%
Preferred shares of beneficial interest, authorized (in shares)			7,000,000
Preferred shares of beneficial interest, par value (in dollars per share) | $ / shares				$ 25.00
NSA OP, LP | Class B Unit | Retirement of Northwest
Class of Stock [Line Items]
Issuance of preferred shares (in shares)				199,975
NSA OP, LP | OP units
Class of Stock [Line Items]
Redemptions of units (in shares)				(261,430)
Unit conversion ratio				1
Minimum conversion period (in years)				1 year
NSA OP, LP | OP units | Common Shares
Class of Stock [Line Items]
Redemptions of units (in shares)				(735,035)
NSA OP, LP | LTIP units
Class of Stock [Line Items]
Issuance of preferred shares (in shares)				144,238
Unit conversion ratio				1
Number of units converted (in units)				144,238
Personal Mini Affiliate | Class B Unit | Personal Mini
Class of Stock [Line Items]
Payments to acquire interest in subsidiaries and affiliates | $		$ 26,100
DownREIT Partnership | OP units
Class of Stock [Line Items]
Unit conversion ratio				1
Minimum conversion period (in years)				5 years
Prior At The Market Sales Agreement
Class of Stock [Line Items]
Value of common and preferred shares authorized under ATM program | $							$ 400,000
At the Market Program
Class of Stock [Line Items]
Value of remaining available offered shares | $				$ 400,000
Series A Cumulative Redeemable Preferred Shares of Beneficial Interest, par value $0.01 per share
Class of Stock [Line Items]
Preferred stock, dividend rate, percentage				6.00%
Preferred shares per share amount of dividends (in dollars per share) | $ / shares				$ 1.50
Series A Cumulative Redeemable Preferred Shares of Beneficial Interest, par value $0.01 per share | Series A-1 preferred units
Class of Stock [Line Items]
Preferred stock, dividend rate, percentage				6.00%
Series A Cumulative Redeemable Preferred Shares of Beneficial Interest, par value $0.01 per share | NSA OP, LP
Class of Stock [Line Items]
Preferred shares cash redemption price (in dollars per share) | $ / shares				$ 25.00
Series A Cumulative Redeemable Preferred Shares of Beneficial Interest, par value $0.01 per share | NSA OP, LP | Series A Preferred Shares
Class of Stock [Line Items]
Redemptions of units (in shares)				(9,387)
Common Shares of Beneficial Interest, $0.01 par value per share | At the Market Program
Class of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)				0	0