SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS - Narrative (Details) $ / shares in Units, $ in Thousands				12 Months Ended
	Jul. 01, 2024 shares	Mar. 16, 2023 USD ($) property shares	Mar. 15, 2023 shares	Dec. 31, 2024 USD ($) property $ / shares shares	Dec. 31, 2023 USD ($) $ / shares shares	Dec. 31, 2022 USD ($) shares	Nov. 19, 2024 USD ($)	Nov. 14, 2024 USD ($)	Jul. 11, 2022 USD ($)	Feb. 27, 2019 USD ($)
Class of Stock [Line Items]
Redemptions/conversions of units (in shares)	11,906,167
Preferred shares of beneficial interest, outstanding (in shares)				14,695,458	14,685,716
Preferred shares of beneficial interest, authorized (in shares)				50,000,000	50,000,000
Preferred units stated value (in dollars per share) | $ / shares				$ 0.01	$ 0.01
Issuance of preferred shares (in shares)	17,984,787			40,200
Number of properties | property				1,074
Series A and B Preferred shares of beneficial interest, shares authorized, issued and outstanding at liquidation preference | $				$ 340,895	$ 340,651
Sales agreement under ATM program | $										$ 169,100
Repurchase amount | $					275,000			$ 350,000	$ 400,000
Repurchase of common shares (in shares)				7,400,322
Stock repurchased | $				$ (275,200)
Repurchase of common shares | $				$ 275,195	$ 310,152	$ 90,109
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%
Common Shares
Class of Stock [Line Items]
Redemptions/conversions of units (in shares)				1,454,837	1,275,854	627,896
Repurchase of common shares (in shares)				7,400,322	8,836,639	1,986,175
Series A Preferred Shares
Class of Stock [Line Items]
Preferred shares of beneficial interest, outstanding (in shares)				9,027,330
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
Class of Stock [Line Items]
Issuance of preferred shares (in shares)				1,548,866
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
Redemption of Series A-1 preferred units (in shares)				9,742
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 units stated value (in dollars per share) | $ / shares				$ 25.00
NSA OP, LP | Subordinated performance units
Class of Stock [Line Items]
Conversion of units, non-voluntary (in units)				7,772,693
NSA OP, LP | Subordinated performance units | Retirement of Northwest
Class of Stock [Line Items]
Issuance of preferred shares (in shares)				309,568
NSA OP, LP | OP units
Class of Stock [Line Items]
Redemptions/conversions of units (in shares)				28,017
Issuance of preferred shares (in shares)				14,376,264
Unit conversion ratio				1
Voluntary conversion of units ( in shares)				43,556
Minimum conversion period (in years)				1 year
NSA OP, LP | OP units | Common Shares
Class of Stock [Line Items]
Redemptions/conversions of units (in shares)				1,454,837
NSA OP, LP | LTIP units
Class of Stock [Line Items]
Issuance of preferred shares (in shares)				92,174
Unit conversion ratio				1
Number of units converted (in units)				92,174
Shares forfeited (in shares)				208,400
NSA OP, LP | Subordinated Performance Units
Class of Stock [Line Items]
Redemptions/conversions of units (in shares)				23,690
Redemption of Series A-1 preferred units (in shares)				194,888
Personal Mini Affiliate | Subordinated performance units | Personal Mini
Class of Stock [Line Items]
Payments to acquire interest in subsidiaries and affiliates | $		$ 26,100
DownREIT Partnership | Subordinated performance units
Class of Stock [Line Items]
Redemptions/conversions of units (in shares)				4,133,474
DownREIT Partnership | OP units
Class of Stock [Line Items]
Issuance of preferred shares (in shares)				3,608,523
Unit conversion ratio				1
Minimum conversion period (in years)				5 years
At the Market Program
Class of Stock [Line Items]
Value of remaining available offered shares | $				$ 400,000
Prior At The Market Sales Agreement
Class of Stock [Line Items]
Value of common and preferred shares authorized under ATM program | $							$ 400,000
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
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/conversions of units (in shares)				9,742