MORTGAGE LOANS AND NOTES PAYABLE - Summary (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Mortgage loans and Notes payable
Principal amount of debt	$ 2,800,000	$ 2,800,000
Total mortgage loans and notes payable	127,239	128,186
Net book value of self-storage facilities	5,938,734	5,951,236
Mortgage Loans
Mortgage loans and Notes payable
Carrying value	120,912	121,368
Plus: Unamortized fair value adjustment	7,103	7,689
Less: Loan procurement costs, net	(776)	(871)
Total mortgage loans and notes payable	127,239	128,186
Net book value of self-storage facilities	354,600	356,100
Annapolis I, MD \| Mortgage Loans
Mortgage loans and Notes payable
Carrying value	$ 4,651	4,703
Effective interest rate (as a percent)	3.78%
Brooklyn XV, NY \| Mortgage Loans
Mortgage loans and Notes payable
Carrying value	$ 14,657	14,746
Effective interest rate (as a percent)	2.15%
Long Island City IV, NY \| Mortgage Loans
Mortgage loans and Notes payable
Carrying value	$ 11,862	11,946
Effective interest rate (as a percent)	2.15%
Long Island City II, NY \| Mortgage Loans
Mortgage loans and Notes payable
Carrying value	$ 17,719	17,834
Effective interest rate (as a percent)	2.25%
Long Island City III, NY \| Mortgage Loans
Mortgage loans and Notes payable
Carrying value	$ 17,723	17,839
Effective interest rate (as a percent)	2.25%
Flushing II, NY \| Mortgage Loans
Mortgage loans and Notes payable
Carrying value	$ 54,300	$ 54,300
Effective interest rate (as a percent)	2.15%

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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