LOANS HELD FOR INVESTMENT - Narrative (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) Loan	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans originated or co-originated | Loan	50
Number of loans repaid or sold | Loan	88
Total Commitment	$ 1,900,000,000
Loans held for investment	1,682,498,000	$ 1,524,873,000	$ 1,726,283,000
Amount funded	679,200,000
Amount of repayments	$ 482,400,000
Percentage of loans held for investment having LIBOR floors	93.00%
Weighted average floor (as a percent)	1.76%
Impairment charges recognized	$ 0	$ 0	$ 0
Senior Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans with outstanding principal | Loan	1
Loan converted to real estate owned	$ 38,600,000