LOANS HELD FOR INVESTMENT - Loans held for Investments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Loans held for investment	$ 2,421,772		$ 2,414,383
Outstanding principal	$ 2,439,373		2,429,112
Weighted Average Unleveraged Effective Yield, Including Non-accrual Loans	5.50%	5.40%
Weighted Average Unleveraged Effective Yield, Excluding Non-accrual Loans	5.60%	5.50%
Weighted average remaining life	1 year 7 months 6 days	1 year 7 months 6 days
Senior mortgage loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Loans held for investment	$ 2,405,013		2,397,655
Outstanding principal	$ 2,421,979		2,411,718
Weighted Average Unleveraged Effective Yield, Including Non-accrual Loans	5.40%	5.30%
Weighted Average Unleveraged Effective Yield, Excluding Non-accrual Loans	5.50%	5.40%
Weighted average remaining life	1 year 6 months	1 year 6 months
Subordinated debt and preferred equity investments
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Loans held for investment	$ 16,759		16,728
Outstanding principal	$ 17,394		$ 17,394
Weighted Average Unleveraged Effective Yield, Including Non-accrual Loans	13.70%	13.70%
Weighted Average Unleveraged Effective Yield, Excluding Non-accrual Loans	13.70%	13.70%
Weighted average remaining life	3 years 9 months 18 days	4 years