INVESTMENTS IN RESIDENTIAL MORTGAGE LOANS - Gain On Sale of Originated Mortgage Loans, Net (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Receivables [Abstract]
Gain on loans originated and sold	$ 403		$ 12,101
Gain (loss) on settlement of mortgage loan origination derivative instruments	(18,318)		(29,741)
MSRs retained on transfer of loans	57,920		94,349
Other	9,499		16,779
Gain on sale of originated mortgage loans, net	$ 49,504	$ 0	$ 93,488	$ 0