SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS - Narrative (Details) $ / shares in Units, $ in Millions				3 Months Ended				6 Months Ended
	Jul. 01, 2024 shares	Mar. 15, 2023	Feb. 27, 2019 USD ($) $ / shares	Jun. 30, 2024 USD ($) $ / shares shares	Mar. 31, 2024 shares	Jun. 30, 2023 shares	Mar. 31, 2023 shares	Jun. 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	$ 0.01
Authorized amount | $										$ 275.0	$ 400.0
Repurchase of common shares (in shares)								7,400,322
Stock repurchased | $								$ (275.2)
Subsequent Event
Class of Stock [Line Items]
Issuance of preferred shares (in shares)	17,984,787
Percentage of cash available for distribution used in conversion ratio calculation	110.00%
Redemptions/conversions of units (in shares)	11,906,167
Time frame prior to conversion for conversion metric (in years)	1 year
Common Shares
Class of Stock [Line Items]
Repurchase of common shares (in shares)				1,908,397	5,491,925		1,622,874
Redemptions/conversions of units (in shares)				205,910	72,802	354,936	67,431
NSA OP, LP
Class of Stock [Line Items]
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 B Preferred Shares | 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
Series A-1 preferred units | NSA OP, LP
Class of Stock [Line Items]
Preferred share/unit dividend rate (percent)								6.00%
Unit conversion ratio								1
Subordinated performance units
Class of Stock [Line Items]
Percentage of cash available for distribution used in conversion ratio calculation								110.00%
Time frame prior to conversion for conversion metric (in years)								1 year
Subordinated performance units | NSA OP, LP
Class of Stock [Line Items]
Unit conversion ratio								1
Redemptions/conversions of units (in shares)								23,690
Unit conversion, lock out period (in years)								2 years
OP units | NSA OP, LP
Class of Stock [Line Items]
Unit conversion ratio				1				1
Issuance of preferred shares (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)								278,712
OP units | DownREIT Partnership
Class of Stock [Line Items]
Unit conversion ratio				1
LTIP units | NSA OP, LP
Class of Stock [Line Items]
Unit conversion ratio				1				1
Issuance of preferred shares (in shares)								176,912
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