MORTGAGE LOANS AND NOTES PAYABLE - Summary (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Mortgage loans and Notes payable
Principal amount of debt	$ 2,800,000	$ 2,800,000
Total mortgage loans and notes payable	129,130	162,918
Net book value of self-storage facilities	5,957,496	6,048,003
Mortgage Loans
Mortgage loans and Notes payable
Carrying value	121,820
Less: Loan procurement costs, net	(967)	(1,269)
Total mortgage loans and notes payable	129,130	162,918
Net book value of self-storage facilities	$ 357,900	442,900
Nashville V, TN \| Mortgage Loans
Mortgage loans and Notes payable
Carrying value		2,148
Effective interest rate (as a percent)	3.85%
New York, NY \| Mortgage Loans
Mortgage loans and Notes payable
Carrying value		28,669
Effective interest rate (as a percent)	3.51%
Annapolis I, MD \| Mortgage Loans
Mortgage loans and Notes payable
Carrying value	$ 4,755	4,906
Effective interest rate (as a percent)	3.78%
Brooklyn XV, NY \| Mortgage Loans
Mortgage loans and Notes payable
Carrying value	$ 14,834	15,093
Effective interest rate (as a percent)	2.15%
Long Island City IV, NY \| Mortgage Loans
Mortgage loans and Notes payable
Carrying value	$ 12,028	12,270
Effective interest rate (as a percent)	2.15%
Long Island City II, NY \| Mortgage Loans
Mortgage loans and Notes payable
Carrying value	$ 17,949	18,283
Effective interest rate (as a percent)	2.25%
Long Island City III, NY \| Mortgage Loans
Mortgage loans and Notes payable
Principal amount of debt	$ 121,820	153,959
Carrying value	$ 17,954	18,290
Effective interest rate (as a percent)	2.25%
Flushing II, NY \| Mortgage Loans
Mortgage loans and Notes payable
Carrying value	$ 54,300	54,300
Plus: Unamortized fair value adjustment	$ 8,277	$ 10,228
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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