INVESTMENTS IN RESIDENTIAL MORTGAGE LOANS - Schedule of Net Interest Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Interest income:
Loans held-for-investment, at fair value	$ 12,647	$ 14,532	$ 40,985	$ 47,167
Total interest income	51,320	86,602	184,223	220,833
Interest expense:
Loans held-for-investment, at fair value	5,326	3,953	15,934	15,717
Total interest expense	30,303	56,563	97,641	152,040
Net interest income	21,017	30,039	86,582	68,793
Acquired Loans, at Lower Cost or Fair Value
Interest income:
Loans Held-for-Sale	7,406	15,426	38,673	43,538
Interest expense:
Loans Held-for-Sale	4,068	9,315	17,501	26,553
Acquired Loans
Interest income:
Loans Held-for-Sale	31,267	56,644	104,565	130,128
Interest expense:
Loans Held-for-Sale	$ 20,909	$ 43,295	$ 64,206	$ 109,770