EXCESS MORTGAGE SERVICING RIGHTS ASSETS - Summary of Direct Investments in Excess MSRs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Schedule of Equity Method Investments [Line Items]
Weighted Average Life (Years)			10 months 24 days
Servicer advance investments | Servicer Advances
Schedule of Equity Method Investments [Line Items]
Residential mortgage loan UPB	$ 21,666,852		$ 21,666,852		$ 26,061,499
Original and Recaptured Pools
Schedule of Equity Method Investments [Line Items]
Original and Recaptured Pools	(4,211)	$ (85)	(8,829)	$ (11,109)
Excess MSRs
Schedule of Equity Method Investments [Line Items]
Residential mortgage loan UPB	64,207,670		$ 64,207,670
Weighted Average Life (Years)			6 years 3 months 18 days
Servicing Asset at Amortized Cost	233,081		$ 233,081
MSRs	284,290		284,290		310,938
Excess MSRs | Agency | Original and Recaptured Pools
Schedule of Equity Method Investments [Line Items]
Residential mortgage loan UPB	30,224,299		$ 30,224,299
Weighted Average Life (Years)			6 years 1 month 6 days
Servicing Asset at Amortized Cost	130,171		$ 130,171
MSRs	$ 146,645		$ 146,645		162,645
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]
Residential mortgage loan UPB	$ 33,983,371		$ 33,983,371
Weighted Average Life (Years)			6 years 7 months 6 days
Servicing Asset at Amortized Cost	102,910		$ 102,910
MSRs	$ 137,645		$ 137,645		$ 148,293
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%