SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Gain (Loss) on Settlement of Investments, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Gain (loss) on sale of real estate securities, net	$ 205,989	$ (29,936)	$ 20,642
Gain (loss) on sale of acquired residential mortgage loans, net	153,174	(7,677)	39,731
Gain (loss) on settlement of derivatives	(129,923)	54,867	(39,214)
Gain (loss) on liquidated residential mortgage loans	(4,872)	(3,734)	(10,201)
Gain (loss) on sale of REO	(11,521)	(12,424)	(9,215)
Gains on settlement of investments in excess MSRs and servicer advance investments	0	113,002	11,320
Other gains (losses)	12,840	(19,013)	(2,753)
Gain (loss) on settlement of investments, net	$ 225,687	$ 95,085	$ 10,310