SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS - Narrative (Details) $ / shares in Units, $ in Millions			3 Months Ended						9 Months Ended
	Jul. 01, 2024 shares	Feb. 27, 2019 USD ($)	Sep. 30, 2024 USD ($) $ / shares shares	Jun. 30, 2024 shares	Mar. 31, 2024 shares	Sep. 30, 2023 shares	Jun. 30, 2023 shares	Mar. 31, 2023 shares	Sep. 30, 2024 USD ($) $ / shares shares	Dec. 31, 2023 $ / shares	Dec. 01, 2023 USD ($)	Jul. 11, 2022 USD ($)	May 19, 2021 USD ($)
Class of Stock [Line Items]
Common shares of beneficial interest, par value (in dollars per share) | $ / shares			$ 0.01						$ 0.01	$ 0.01
Authorized amount | $											$ 275.0	$ 400.0
Repurchase of common shares (in shares)									7,400,322
Stock repurchased | $									$ (275.2)
Preferred units stated value (in dollars per share) | $ / shares			$ 0.01						$ 0.01	$ 0.01
Issuance of preferred shares (in shares)	17,984,787								40,200
Redemptions/conversions of units (in shares)	11,906,167
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]
Repurchase of common shares (in shares)				1,908,397	5,491,925	6,360,994		1,622,874
Redemptions/conversions of units (in shares)			1,048,202	205,910	72,802	667,484	354,936	67,431
Series A preferred shares
Class of Stock [Line Items]
Preferred dividends in arrears (in dollar per share) | $ / shares									$ 1.50
NSA OP, LP
Class of Stock [Line Items]
Issuance of preferred shares (in shares)									1,548,866
Redemptions/conversions of units (in shares)									194,888
NSA OP, LP | Series A preferred shares
Class of Stock [Line Items]
Preferred units cash redemption price (in dollars per share) | $ / shares			$ 25.00						$ 25.00
Series A Preferred Shares | NSA OP, LP | Series A preferred shares
Class of Stock [Line Items]
Redemptions/conversions of units (in shares)									6,665
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) | $ / shares			$ 25.00						$ 25.00
Unit conversion ratio									1
Series A-1 preferred units | NSA OP, LP | Series A preferred shares
Class of Stock [Line Items]
Redemptions/conversions of units (in shares)									6,665
Subordinated performance units | NSA OP, LP
Class of Stock [Line Items]
Issuance of shares/units, non-voluntary (in shares)									7,772,693
Subordinated performance units | DownREIT Partnership
Class of Stock [Line Items]
Redemptions/conversions of units (in shares)									4,133,474
OP units | NSA OP, LP
Class of Stock [Line Items]
Unit conversion ratio			1						1
Issuance of preferred shares (in shares)									14,376,264
Voluntary conversion of units (in shares)									43,556
Redemptions/conversions of units (in shares)									28,017
OP units | NSA OP, LP | Common Shares
Class of Stock [Line Items]
Redemptions/conversions of units (in shares)									1,326,914
OP units | DownREIT Partnership
Class of Stock [Line Items]
Unit conversion ratio			1
Issuance of preferred shares (in shares)									3,608,523
Subordinated Performance Units | NSA OP, LP
Class of Stock [Line Items]
Redemptions/conversions of units (in shares)									23,690
LTIP units | NSA OP, LP
Class of Stock [Line Items]
Unit conversion ratio			1						1
Issuance of preferred shares (in shares)									176,974
Conversion of units (in shares)									92,174
Prior Sales Agreement
Class of Stock [Line Items]
Value of common and preferred shares authorized under ATM program | $		$ 250.0
Preferred share/unit dividend rate (percent)		6.00%
At The Market Program
Class of Stock [Line Items]
Value of common and preferred shares authorized under ATM program | $													$ 400.0
Value of remaining available offered shares | $			$ 169.1						$ 169.1				$ 31.0
At The Market Program | Common Shares of Beneficial Interest, $0.01 par value per share
Class of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)									0