INVESTMENTS IN EXCESS MORTGAGE SERVICING RIGHTS - Summary of Investments in Excess MSRs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Investment [Line Items]
UPB of Underlying Mortgages	$ 103,000,000
Weighted Average Life (Years)	10 months 29 days
Changes in fair value recorded in other income	$ (58,656)	$ 4,322	$ (7,297)
Corporate Joint Venture | Consumer loan bonds
Investment [Line Items]
UPB of Underlying Mortgages	40,096,998	139,460,371
Original and Recaptured Pools
Investment [Line Items]
Changes in fair value recorded in other income	(50,030)	(5,630)	(11,221)
Recapture Agreements
Investment [Line Items]
Changes in fair value recorded in other income	(8,626)	9,952	3,924
Excess MSRs
Investment [Line Items]
UPB of Underlying Mortgages	$ 106,426,363	$ 217,121,299
Weighted Average Life (Years)	6 years 1 month 6 days	6 years 4 months 24 days
Amortized Cost Basis	$ 361,327	$ 1,028,523
Carrying Value	447,860	1,173,713	1,399,455
Excess MSRs | Nationstar
Investment [Line Items]
Carrying Value	445,328	532,233	$ 611,293
Excess MSRs | Agency
Investment [Line Items]
UPB of Underlying Mortgages	$ 52,368,290	$ 63,839,281
Weighted Average Life (Years)	6 years 1 month 6 days	6 years 2 months 12 days
Amortized Cost Basis	$ 218,797	$ 267,947
Carrying Value	257,387	324,636
Excess MSRs | Agency | Original and Recaptured Pools
Investment [Line Items]
UPB of Underlying Mortgages	$ 52,368,290	$ 63,839,281
Weighted Average Life (Years)	5 years 7 months 6 days	5 years 9 months 18 days
Amortized Cost Basis	$ 203,675	$ 249,003
Carrying Value	$ 226,452	$ 280,033
Excess MSRs | Agency | Original and Recaptured Pools | Minimum
Investment [Line Items]
Interest in Excess MSR	32.50%	32.50%
Excess MSRs | Agency | Original and Recaptured Pools | Maximum
Investment [Line Items]
Interest in Excess MSR	66.70%	66.70%
Excess MSRs | Agency | Original and Recaptured Pools | Weighted Average
Investment [Line Items]
Interest in Excess MSR	53.30%	53.50%
Excess MSRs | Agency | Original and Recaptured Pools | Fortress-managed funds | Minimum
Investment [Line Items]
Interest in Excess MSR	0.00%	0.00%
Excess MSRs | Agency | Original and Recaptured Pools | Fortress-managed funds | Maximum
Investment [Line Items]
Interest in Excess MSR	40.00%	40.00%
Excess MSRs | Agency | Original and Recaptured Pools | Nationstar | Minimum
Investment [Line Items]
Interest in Excess MSR	20.00%	20.00%
Excess MSRs | Agency | Original and Recaptured Pools | Nationstar | Maximum
Investment [Line Items]
Interest in Excess MSR	35.00%	35.00%
Excess MSRs | Agency | Recapture Agreements
Investment [Line Items]
UPB of Underlying Mortgages	$ 0	$ 0
Weighted Average Life (Years)	12 years 9 months 18 days	11 years 4 months 24 days
Amortized Cost Basis	$ 15,122	$ 18,944
Carrying Value	$ 30,935	$ 44,603
Excess MSRs | Agency | Recapture Agreements | Minimum
Investment [Line Items]
Interest in Excess MSR	32.50%	32.50%
Excess MSRs | Agency | Recapture Agreements | Maximum
Investment [Line Items]
Interest in Excess MSR	66.70%	66.70%
Excess MSRs | Agency | Recapture Agreements | Weighted Average
Investment [Line Items]
Interest in Excess MSR	53.30%	53.50%
Excess MSRs | Agency | Recapture Agreements | Fortress-managed funds | Minimum
Investment [Line Items]
Interest in Excess MSR	0.00%	0.00%
Excess MSRs | Agency | Recapture Agreements | Fortress-managed funds | Maximum
Investment [Line Items]
Interest in Excess MSR	40.00%	40.00%
Excess MSRs | Agency | Recapture Agreements | Nationstar | Minimum
Investment [Line Items]
Interest in Excess MSR	20.00%	20.00%
Excess MSRs | Agency | Recapture Agreements | Nationstar | Maximum
Investment [Line Items]
Interest in Excess MSR	35.00%	35.00%
Excess MSRs | Non-Agency
Investment [Line Items]
UPB of Underlying Mortgages	$ 54,058,073	$ 153,282,018
Weighted Average Life (Years)	6 years	6 years 4 months 24 days
Amortized Cost Basis	$ 142,530	$ 760,576
Carrying Value	190,473	849,077
Excess MSRs | Non-Agency | Original and Recaptured Pools
Investment [Line Items]
UPB of Underlying Mortgages	$ 54,058,073	$ 64,146,430
Weighted Average Life (Years)	5 years 9 months 18 days	5 years 4 months 24 days
Amortized Cost Basis	$ 138,314	$ 154,938
Carrying Value	$ 172,712	$ 190,696
Excess MSRs | Non-Agency | Original and Recaptured Pools | Minimum
Investment [Line Items]
Interest in Excess MSR	33.30%	33.30%
Excess MSRs | Non-Agency | Original and Recaptured Pools | Maximum
Investment [Line Items]
Interest in Excess MSR	100.00%	100.00%
Excess MSRs | Non-Agency | Original and Recaptured Pools | Weighted Average
Investment [Line Items]
Interest in Excess MSR	59.40%	59.60%
Excess MSRs | Non-Agency | Original and Recaptured Pools | Fortress-managed funds | Minimum
Investment [Line Items]
Interest in Excess MSR	0.00%	0.00%
Excess MSRs | Non-Agency | Original and Recaptured Pools | Fortress-managed funds | Maximum
Investment [Line Items]
Interest in Excess MSR	50.00%	50.00%
Excess MSRs | Non-Agency | Original and Recaptured Pools | Nationstar | Minimum
Investment [Line Items]
Interest in Excess MSR	0.00%	0.00%
Excess MSRs | Non-Agency | Original and Recaptured Pools | Nationstar | Maximum
Investment [Line Items]
Interest in Excess MSR	33.30%	33.30%
Excess MSRs | Non-Agency | Recapture Agreements
Investment [Line Items]
UPB of Underlying Mortgages	$ 0	$ 0
Weighted Average Life (Years)	12 years 9 months 18 days	11 years 3 months 18 days
Amortized Cost Basis	$ 4,216	$ 7,489
Carrying Value	$ 17,761	$ 19,814
Excess MSRs | Non-Agency | Recapture Agreements | Minimum
Investment [Line Items]
Interest in Excess MSR	33.30%	33.30%
Excess MSRs | Non-Agency | Recapture Agreements | Maximum
Investment [Line Items]
Interest in Excess MSR	100.00%	100.00%
Excess MSRs | Non-Agency | Recapture Agreements | Weighted Average
Investment [Line Items]
Interest in Excess MSR	59.40%	59.60%
Excess MSRs | Non-Agency | Recapture Agreements | Fortress-managed funds | Minimum
Investment [Line Items]
Interest in Excess MSR	0.00%	0.00%
Excess MSRs | Non-Agency | Recapture Agreements | Fortress-managed funds | Maximum
Investment [Line Items]
Interest in Excess MSR	50.00%	50.00%
Excess MSRs | Non-Agency | Recapture Agreements | Nationstar | Minimum
Investment [Line Items]
Interest in Excess MSR	0.00%	0.00%
Excess MSRs | Non-Agency | Recapture Agreements | Nationstar | Maximum
Investment [Line Items]
Interest in Excess MSR	33.30%	33.30%
Excess MSRs | Non-Agency | Ocwen Serviced Pools
Investment [Line Items]
UPB of Underlying Mortgages		$ 89,135,588
Interest in Excess MSR		100.00%
Weighted Average Life (Years)		6 years 6 months
Amortized Cost Basis		$ 598,149
Carrying Value		$ 638,567
Excess MSRs | Non-Agency | Ocwen Serviced Pools | Fortress-managed funds
Investment [Line Items]
Interest in Excess MSR		0.00%
Excess MSRs | Non-Agency | Ocwen Serviced Pools | Nationstar
Investment [Line Items]
Interest in Excess MSR		0.00%