INVESTMENTS IN EXCESS MORTGAGE SERVICING RIGHTS ASSETS - Summary of Direct Investments in Excess MSRs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Weighted Average Life (Years)			2 years 3 months 18 days
Carrying Value	$ 4,781,624		$ 4,781,624		$ 5,686,233
Servicer advance investments | Servicer Advances
Schedule of Equity Method Investments [Line Items]
UPB of Underlying Mortgages	27,484,426		27,484,426		31,442,267
Original and Recaptured Pools
Schedule of Equity Method Investments [Line Items]
Original and Recaptured Pools	(664)	$ 2,407	(11,773)	$ (1,421)
Excess MSRs
Schedule of Equity Method Investments [Line Items]
UPB of Underlying Mortgages	77,351,569		$ 77,351,569
Weighted Average Life (Years)			6 years 1 month 6 days
Servicing Asset at Amortized Cost	264,127		$ 264,127
Carrying Value	328,623		328,623		379,747
Excess MSRs | Mr. Cooper
Schedule of Equity Method Investments [Line Items]
Carrying Value	326,704		326,704		377,692
Excess MSRs | Agency | Original and Recaptured Pools
Schedule of Equity Method Investments [Line Items]
UPB of Underlying Mortgages	37,356,300		$ 37,356,300
Weighted Average Life (Years)			5 years 9 months 18 days
Servicing Asset at Amortized Cost	150,403		$ 150,403
Carrying Value	$ 173,549		$ 173,549		209,633
Excess MSRs | Agency | Original and Recaptured Pools | Minimum
Schedule of Equity Method Investments [Line Items]
Interest in Excess MSR	32.50%		32.50%
Excess MSRs | Agency | Original and Recaptured Pools | Maximum
Schedule of Equity Method Investments [Line Items]
Interest in Excess MSR	66.70%		66.70%
Excess MSRs | Agency | Original and Recaptured Pools | Weighted Average
Schedule of Equity Method Investments [Line Items]
Interest in Excess MSR	53.30%		53.30%
Excess MSRs | Agency | Fortress-managed funds | Original and Recaptured Pools | Minimum
Schedule of Equity Method Investments [Line Items]
Interest in Excess MSR	0.00%		0.00%
Excess MSRs | Agency | Fortress-managed funds | Original and Recaptured Pools | Maximum
Schedule of Equity Method Investments [Line Items]
Interest in Excess MSR	40.00%		40.00%
Excess MSRs | Agency | Mr. Cooper | Original and Recaptured Pools | Minimum
Schedule of Equity Method Investments [Line Items]
Interest in Excess MSR	20.00%		20.00%
Excess MSRs | Agency | Mr. Cooper | Original and Recaptured Pools | Maximum
Schedule of Equity Method Investments [Line Items]
Interest in Excess MSR	35.00%		35.00%
Excess MSRs | Non-Agency | Original and Recaptured Pools
Schedule of Equity Method Investments [Line Items]
UPB of Underlying Mortgages	$ 39,995,269		$ 39,995,269
Weighted Average Life (Years)			6 years 7 months 6 days
Servicing Asset at Amortized Cost	113,724		$ 113,724
Carrying Value	$ 155,074		$ 155,074		$ 170,114
Excess MSRs | Non-Agency | Original and Recaptured Pools | Minimum
Schedule of Equity Method Investments [Line Items]
Interest in Excess MSR	33.30%		33.30%
Excess MSRs | Non-Agency | Original and Recaptured Pools | Maximum
Schedule of Equity Method Investments [Line Items]
Interest in Excess MSR	100.00%		100.00%
Excess MSRs | Non-Agency | Original and Recaptured Pools | Weighted Average
Schedule of Equity Method Investments [Line Items]
Interest in Excess MSR	59.40%		59.40%
Excess MSRs | Non-Agency | Fortress-managed funds | Original and Recaptured Pools | Minimum
Schedule of Equity Method Investments [Line Items]
Interest in Excess MSR	0.00%		0.00%
Excess MSRs | Non-Agency | Fortress-managed funds | Original and Recaptured Pools | Maximum
Schedule of Equity Method Investments [Line Items]
Interest in Excess MSR	50.00%		50.00%
Excess MSRs | Non-Agency | Mr. Cooper | Original and Recaptured Pools | Minimum
Schedule of Equity Method Investments [Line Items]
Interest in Excess MSR	0.00%		0.00%
Excess MSRs | Non-Agency | Mr. Cooper | Original and Recaptured Pools | Maximum
Schedule of Equity Method Investments [Line Items]
Interest in Excess MSR	33.30%		33.30%