LOANS HELD-FOR-INVESTMENT (Schedule of Loans Held for Investment) (Details) - USD ($)	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held-for-investment and related receivables, net	$ 892,895,000			$ 301,630,000
Less: Allowance for credit losses	(35,039,000)	$ (27,684,000)	$ (19,779,000)	0
Total loans held-for-investment and related receivables, net	857,856,000			301,630,000
Mezzanine Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held-for-investment and related receivables, net	146,516,000			146,060,000
Less: Allowance for credit losses	(24,870,000)	(21,269,000)	(14,541,000)	0
Total loans held-for-investment and related receivables, net	121,600,000
Senior Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held-for-investment and related receivables, net	327,244,000			152,820,000
Less: Allowance for credit losses	(1,882,000)	(492,000)	(809,000)	0
Total CRE loans-held-for-investment and related receivables, net
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held-for-investment and related receivables, net	473,760,000			298,880,000
Total loans held-for-investment and related receivables, net	447,008,000			298,880,000
Broadly Syndicated Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held-for-investment and related receivables, net	419,135,000			2,750,000
Less: Allowance for credit losses	(8,287,000)	$ (5,923,000)	$ (4,429,000)	0
Total loans held-for-investment and related receivables, net	$ 410,848,000			$ 2,750,000