INVESTMENTS IN EXCESS MORTGAGE SERVICING RIGHTS - Summary of Direct Investments in Excess MSRs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Investment [Line Items]
Weighted Average Life (Years)	1 year 4 months 30 days
Principal investment gain (loss)	$ (45,691)	$ 821
Servicer Advance Investments | Servicer Advances
Investment [Line Items]
UPB of Underlying Mortgages	47,831,952		$ 139,460,371
MSRs
Investment [Line Items]
UPB of Underlying Mortgages	$ 197,462,949
Weighted Average Life (Years)	6 years 5 months 4 days
Amortized Cost Basis	$ 1,740,698
Carrying Value	2,129,665
Original and Recaptured Pools
Investment [Line Items]
Principal investment gain (loss)	(43,122)	(7,248)
Recapture Agreements
Investment [Line Items]
Principal investment gain (loss)	(2,569)	$ 8,069
Agency | MSRs
Investment [Line Items]
UPB of Underlying Mortgages	$ 197,403,568
Weighted Average Life (Years)	6 years 5 months 4 days
Amortized Cost Basis	$ 1,740,698
Carrying Value	2,129,665
Non-Agency | MSRs
Investment [Line Items]
UPB of Underlying Mortgages	$ 59,381
Weighted Average Life (Years)	6 years 3 months 14 days
Amortized Cost Basis	$ 0
Carrying Value	0
Excess MSRs
Investment [Line Items]
UPB of Underlying Mortgages	$ 124,900,750
Weighted Average Life (Years)	6 years
Amortized Cost Basis	$ 416,178
Carrying Value	515,676		1,173,713
Excess MSRs | Ocwen
Investment [Line Items]
Carrying Value	0		638,567
Excess MSRs | Nationstar
Investment [Line Items]
Carrying Value	512,876		532,233
Excess MSRs | Agency
Investment [Line Items]
UPB of Underlying Mortgages	$ 62,526,609
Weighted Average Life (Years)	6 years 3 months 18 days
Amortized Cost Basis	$ 259,864
Carrying Value	313,385		324,636
Excess MSRs | Agency | Original and Recaptured Pools
Investment [Line Items]
UPB of Underlying Mortgages	$ 62,526,609
Weighted Average Life (Years)	5 years 9 months 18 days
Amortized Cost Basis	$ 242,028
Carrying Value	$ 271,623		280,033
Excess MSRs | Agency | Original and Recaptured Pools | Minimum
Investment [Line Items]
Interest in Excess MSR	32.50%
Excess MSRs | Agency | Original and Recaptured Pools | Maximum
Investment [Line Items]
Interest in Excess MSR	66.70%
Excess MSRs | Agency | Original and Recaptured Pools | Weighted Average
Investment [Line Items]
Interest in Excess MSR	53.30%
Excess MSRs | Agency | Recapture Agreements
Investment [Line Items]
UPB of Underlying Mortgages	$ 0
Weighted Average Life (Years)	12 years 6 months
Amortized Cost Basis	$ 17,836
Carrying Value	$ 41,762		44,603
Excess MSRs | Agency | Recapture Agreements | Minimum
Investment [Line Items]
Interest in Excess MSR	32.50%
Excess MSRs | Agency | Recapture Agreements | Maximum
Investment [Line Items]
Interest in Excess MSR	66.70%
Excess MSRs | Agency | Recapture Agreements | Weighted Average
Investment [Line Items]
Interest in Excess MSR	53.30%
Excess MSRs | Agency | Fortress-managed funds | Original and Recaptured Pools | Minimum
Investment [Line Items]
Interest in Excess MSR	0.00%
Excess MSRs | Agency | Fortress-managed funds | Original and Recaptured Pools | Maximum
Investment [Line Items]
Interest in Excess MSR	40.00%
Excess MSRs | Agency | Fortress-managed funds | Recapture Agreements | Minimum
Investment [Line Items]
Interest in Excess MSR	0.00%
Excess MSRs | Agency | Fortress-managed funds | Recapture Agreements | Maximum
Investment [Line Items]
Interest in Excess MSR	40.00%
Excess MSRs | Agency | Nationstar | Original and Recaptured Pools | Minimum
Investment [Line Items]
Interest in Excess MSR	20.00%
Excess MSRs | Agency | Nationstar | Original and Recaptured Pools | Maximum
Investment [Line Items]
Interest in Excess MSR	35.00%
Excess MSRs | Agency | Nationstar | Recapture Agreements | Minimum
Investment [Line Items]
Interest in Excess MSR	20.00%
Excess MSRs | Agency | Nationstar | Recapture Agreements | Maximum
Investment [Line Items]
Interest in Excess MSR	35.00%
Excess MSRs | Non-Agency
Investment [Line Items]
UPB of Underlying Mortgages	$ 62,374,141
Weighted Average Life (Years)	5 years 7 months 6 days
Amortized Cost Basis	$ 156,314
Carrying Value	202,291		849,077
Excess MSRs | Non-Agency | Original and Recaptured Pools
Investment [Line Items]
UPB of Underlying Mortgages	$ 62,374,141
Weighted Average Life (Years)	5 years 3 months 18 days
Amortized Cost Basis	$ 149,606
Carrying Value	$ 184,094		190,696
Excess MSRs | Non-Agency | Original and Recaptured Pools | Minimum
Investment [Line Items]
Interest in Excess MSR	33.30%
Excess MSRs | Non-Agency | Original and Recaptured Pools | Maximum
Investment [Line Items]
Interest in Excess MSR	100.00%
Excess MSRs | Non-Agency | Original and Recaptured Pools | Weighted Average
Investment [Line Items]
Interest in Excess MSR	59.40%
Excess MSRs | Non-Agency | Recapture Agreements
Investment [Line Items]
UPB of Underlying Mortgages	$ 0
Weighted Average Life (Years)	12 years 4 months 24 days
Amortized Cost Basis	$ 6,708
Carrying Value	$ 18,197		19,814
Excess MSRs | Non-Agency | Recapture Agreements | Minimum
Investment [Line Items]
Interest in Excess MSR	33.30%
Excess MSRs | Non-Agency | Recapture Agreements | Maximum
Investment [Line Items]
Interest in Excess MSR	100.00%
Excess MSRs | Non-Agency | Recapture Agreements | Weighted Average
Investment [Line Items]
Interest in Excess MSR	59.40%
Excess MSRs | Non-Agency | Ocwen Serviced Pools
Investment [Line Items]
UPB of Underlying Mortgages	$ 0
Interest in Excess MSR	100.00%
Weighted Average Life (Years)	0 years
Amortized Cost Basis	$ 0
Carrying Value	$ 0		$ 638,567
Excess MSRs | Non-Agency | Fortress-managed funds | Original and Recaptured Pools | Minimum
Investment [Line Items]
Interest in Excess MSR	0.00%
Excess MSRs | Non-Agency | Fortress-managed funds | Original and Recaptured Pools | Maximum
Investment [Line Items]
Interest in Excess MSR	50.00%
Excess MSRs | Non-Agency | Fortress-managed funds | Recapture Agreements | Minimum
Investment [Line Items]
Interest in Excess MSR	0.00%
Excess MSRs | Non-Agency | Fortress-managed funds | Recapture Agreements | Maximum
Investment [Line Items]
Interest in Excess MSR	50.00%
Excess MSRs | Non-Agency | Fortress-managed funds | Ocwen Serviced Pools
Investment [Line Items]
Interest in Excess MSR	0.00%
Excess MSRs | Non-Agency | Nationstar | Original and Recaptured Pools | Minimum
Investment [Line Items]
Interest in Excess MSR	0.00%
Excess MSRs | Non-Agency | Nationstar | Original and Recaptured Pools | Maximum
Investment [Line Items]
Interest in Excess MSR	33.30%
Excess MSRs | Non-Agency | Nationstar | Recapture Agreements | Minimum
Investment [Line Items]
Interest in Excess MSR	0.00%
Excess MSRs | Non-Agency | Nationstar | Recapture Agreements | Maximum
Investment [Line Items]
Interest in Excess MSR	33.30%
Excess MSRs | Non-Agency | Nationstar | Ocwen Serviced Pools
Investment [Line Items]
Interest in Excess MSR	0.00%
Excess MSRs Investees
Investment [Line Items]
UPB of Underlying Mortgages	$ 49,435,804
Weighted Average Life (Years)	6 years 1 month 11 days
Amortized Cost Basis	$ 226,481
Carrying Value	309,322
Excess MSRs Investees | Agency | Original and Recaptured Pools
Investment [Line Items]
UPB of Underlying Mortgages	$ 49,435,804
Weighted Average Life (Years)	5 years 5 months 4 days
Amortized Cost Basis	$ 203,978
Carrying Value	262,014
Excess MSRs Investees | Agency | Recapture Agreements
Investment [Line Items]
UPB of Underlying Mortgages	$ 0
Weighted Average Life (Years)	12 years 3 months 30 days
Amortized Cost Basis	$ 22,503
Carrying Value	$ 47,308