BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Loans (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Jan. 01, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Unamortized retained loan discounts	$ 8,300				$ 9,000
Loan receivable, nonaccrual, past due period (more than)	60 days
Cumulative-effective adjustment	$ 375,260	$ 381,322	$ 378,682		362,033	$ 372,144	$ 387,006	$ 377,460	$ 373,549
Allowance for credit losses	1,704	1,713	1,940		1,106
Distributions in Excess of Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effective adjustment	$ (903,725)	$ (878,854)	$ (853,108)		(837,846)	$ (823,523)	$ (809,157)	$ (806,923)	$ (804,227)
Cumulative-effect adjustment upon adoption of ASU 2016-13 (Note 2)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effective adjustment					(619)
Allowance for credit losses					783
Cumulative-effect adjustment upon adoption of ASU 2016-13 (Note 2) | Distributions in Excess of Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effective adjustment				$ (619)	$ (619)
CECL reserve transition gross				(783)
CECL reserve transition, deferred tax asset				$ 164