COMMERCIAL LOAN AND MASTER LEASE INVESTMENTS - Summary of Commercial Loan Investments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Mortgage Loans On Real Estate [Line Items]
Original Face Amount	$ 37,735	$ 37,735
Current Face Amount	37,735	37,735
Carrying Value	38,417	38,320
Master Tenant - Hialeah Lease Loan - Hialeah FL]
Mortgage Loans On Real Estate [Line Items]
Original Face Amount	21,085	21,085
Current Face Amount	21,085	21,085
Carrying Value	21,109	21,101
Mortgage Note - 4311 Maple Avenue, Dallas, TX
Mortgage Loans On Real Estate [Line Items]
Original Face Amount	400	400
Current Face Amount	400	400
Carrying Value	$ 393	$ 392
Coupon Rate	7.50%	7.50%
Ground Lease Loan - 400 Josephine Street, Austin, TX
Mortgage Loans On Real Estate [Line Items]
Original Face Amount	$ 16,250	$ 16,250
Current Face Amount	16,250	16,250
Carrying Value	$ 16,915	$ 16,827