SIGNIFICANT ACCOUNTING POLICIES - Schedule of Interest Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest expense	$ 62,583	$ 63,002	$ 51,193
Secured funding agreements
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest expense	32,859	43,039	29,272
Notes Payable
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest expense	867	0	0
Interest Expense from Real Estate Owned	28,300
Securitizations debt
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest expense	19,950	11,434	8,330
Secured term loan
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Interest expense	$ 8,907	$ 8,529	$ 13,591