MORTGAGE LOANS AND NOTES PAYABLE - Summary (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2026	Dec. 31, 2025
MORTGAGE LOANS AND NOTES PAYABLE
Principal amount of debt	$ 2,950,000	$ 2,950,000
Total mortgage loans and notes payable	97,637	98,859
Net book value of self-storage facilities	6,306,484	6,375,849
Mortgage Loans
MORTGAGE LOANS AND NOTES PAYABLE
Carrying value	94,675
Principal amount of debt	94,675	95,286
Plus: Unamortized fair value adjustment	3,255	3,969
Less: Loan procurement costs, net	(293)	(396)
Total mortgage loans and notes payable	97,637	98,859
Net book value of self-storage facilities	237,400	240,000
Long Island City II, NY \| Mortgage Loans
MORTGAGE LOANS AND NOTES PAYABLE
Carrying value	$ 16,627	16,880
Effective interest rate (as a percent)	2.25%
Long Island City III, NY \| Mortgage Loans
MORTGAGE LOANS AND NOTES PAYABLE
Carrying value	$ 16,626	16,880
Effective interest rate (as a percent)	2.25%
Allen, TX \| Mortgage Loans
MORTGAGE LOANS AND NOTES PAYABLE
Carrying value	$ 7,122	7,226
Effective interest rate (as a percent)	6.29%
Flushing II, NY \| Mortgage Loans
MORTGAGE LOANS AND NOTES PAYABLE
Carrying value	$ 54,300	$ 54,300
Effective interest rate (as a percent)	2.15%
Joint Venture
MORTGAGE LOANS AND NOTES PAYABLE
Ownership interest held by the entity (as a percent)	85.00%	85.00%

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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