INVESTMENTS IN RESIDENTIAL MORTGAGE LOANS - Gain On Sale of Originated Mortgage Loans, Net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Receivables [Abstract]
Gain on loans originated and sold			$ 24,684
Gain (loss) on settlement of mortgage loan origination derivative instruments			(2,757)
MSRs retained on transfer of loans			17,282
Other			6,523
Gain on sale of originated mortgage loans, net	$ 45,732	$ 0	$ 45,732	$ 0