RESIDENTIAL MORTGAGE LOANS - Schedule of Net Interest Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Interest income:
Loans held-for-investment, at fair value	$ 44,369	$ 53,264	$ 60,301
Loans held-for-sale, at lower of cost or fair value	23,280	50,130	65,926
Loans held-for-sale, at fair value	260,062	135,729	175,926
Total interest income	327,711	239,123	302,153
Interest expense:
Loans held-for-investment, at fair value	16,919	21,029	19,381
Loans held-for-sale, at lower of cost or fair value	21,333	22,541	40,067
Loans held-for-sale, at fair value	159,413	90,064	109,723
Total interest expense	197,665	133,634	169,171
Net interest income	$ 130,046	$ 105,489	$ 132,982