Quarterly report pursuant to Section 13 or 15(d)

INVESTMENTS IN EXCESS MORTGAGE SERVICING RIGHTS - Summary of Direct Investments in Excess MSRs (Details)

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INVESTMENTS IN EXCESS MORTGAGE SERVICING RIGHTS - Summary of Direct Investments in Excess MSRs (Details) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Dec. 31, 2017
Investment [Line Items]          
Weighted Average Life (Years)     1 year 3 months 21 days    
Principal investment gain (loss) $ (5,276) $ (19,180) $ (50,967) $ (18,359)  
Servicer Advance Investments | Servicer Advances          
Investment [Line Items]          
UPB of Underlying Mortgages 44,895,549   44,895,549   $ 139,460,371
Original and Recaptured Pools          
Investment [Line Items]          
Principal investment gain (loss) (2,567) (21,736) (45,689) (28,984)  
Recapture Agreements          
Investment [Line Items]          
Principal investment gain (loss) (2,709) $ 2,556 (5,278) $ 10,625  
Excess MSRs          
Investment [Line Items]          
UPB of Underlying Mortgages 119,341,194   $ 119,341,194    
Weighted Average Life (Years)     6 years 1 month 6 days    
Amortized Cost Basis 401,077   $ 401,077    
Carrying Value 495,299   495,299   1,173,713
Excess MSRs | Nationstar          
Investment [Line Items]          
Carrying Value 492,888   492,888   532,233
Excess MSRs | Agency          
Investment [Line Items]          
UPB of Underlying Mortgages 60,151,459   $ 60,151,459    
Weighted Average Life (Years)     6 years 3 months 18 days    
Amortized Cost Basis 250,499   $ 250,499    
Carrying Value 299,571   299,571   324,636
Excess MSRs | Agency | Original and Recaptured Pools          
Investment [Line Items]          
UPB of Underlying Mortgages 60,151,459   $ 60,151,459    
Weighted Average Life (Years)     5 years 9 months 18 days    
Amortized Cost Basis 233,707   $ 233,707    
Carrying Value $ 261,558   $ 261,558   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%   53.30%    
Excess MSRs | Agency | Recapture Agreements          
Investment [Line Items]          
UPB of Underlying Mortgages $ 0   $ 0    
Weighted Average Life (Years)     13 years    
Amortized Cost Basis 16,792   $ 16,792    
Carrying Value $ 38,013   $ 38,013   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%   53.30%    
Excess MSRs | Agency | Fortress-managed funds | Original and Recaptured Pools | Minimum          
Investment [Line Items]          
Interest in Excess MSR 0.00%   0.00%    
Excess MSRs | Agency | Fortress-managed funds | Original and Recaptured Pools | Maximum          
Investment [Line Items]          
Interest in Excess MSR 40.00%   40.00%    
Excess MSRs | Agency | Fortress-managed funds | Recapture Agreements | Minimum          
Investment [Line Items]          
Interest in Excess MSR 0.00%   0.00%    
Excess MSRs | Agency | Fortress-managed funds | Recapture Agreements | Maximum          
Investment [Line Items]          
Interest in Excess MSR 40.00%   40.00%    
Excess MSRs | Agency | Nationstar | Original and Recaptured Pools | Minimum          
Investment [Line Items]          
Interest in Excess MSR 20.00%   20.00%    
Excess MSRs | Agency | Nationstar | Original and Recaptured Pools | Maximum          
Investment [Line Items]          
Interest in Excess MSR 35.00%   35.00%    
Excess MSRs | Agency | Nationstar | Recapture Agreements | Minimum          
Investment [Line Items]          
Interest in Excess MSR 20.00%   20.00%    
Excess MSRs | Agency | Nationstar | Recapture Agreements | Maximum          
Investment [Line Items]          
Interest in Excess MSR 35.00%   35.00%    
Excess MSRs | Non-Agency          
Investment [Line Items]          
UPB of Underlying Mortgages $ 59,189,735   $ 59,189,735    
Weighted Average Life (Years)     5 years 10 months 24 days    
Amortized Cost Basis 150,578   $ 150,578    
Carrying Value 195,728   195,728   849,077
Excess MSRs | Non-Agency | Original and Recaptured Pools          
Investment [Line Items]          
UPB of Underlying Mortgages 59,189,735   $ 59,189,735    
Weighted Average Life (Years)     5 years 7 months 6 days    
Amortized Cost Basis 144,681   $ 144,681    
Carrying Value $ 178,345   $ 178,345   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%   59.40%    
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    
Amortized Cost Basis 5,897   $ 5,897    
Carrying Value $ 17,383   $ 17,383   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%   59.40%    
Excess MSRs | Non-Agency | Ocwen Serviced Pools          
Investment [Line Items]          
UPB of Underlying Mortgages $ 0   $ 0    
Interest in Excess MSR 0.00%   0.00%    
Weighted Average Life (Years)     0 years    
Amortized Cost Basis $ 0   $ 0    
Carrying Value $ 0   $ 0   $ 638,567
Excess MSRs | Non-Agency | Fortress-managed funds | Original and Recaptured Pools | Minimum          
Investment [Line Items]          
Interest in Excess MSR 0.00%   0.00%    
Excess MSRs | Non-Agency | Fortress-managed funds | Original and Recaptured Pools | Maximum          
Investment [Line Items]          
Interest in Excess MSR 50.00%   50.00%    
Excess MSRs | Non-Agency | Fortress-managed funds | Recapture Agreements | Minimum          
Investment [Line Items]          
Interest in Excess MSR 0.00%   0.00%    
Excess MSRs | Non-Agency | Fortress-managed funds | Recapture Agreements | Maximum          
Investment [Line Items]          
Interest in Excess MSR 50.00%   50.00%    
Excess MSRs | Non-Agency | Fortress-managed funds | Ocwen Serviced Pools          
Investment [Line Items]          
Interest in Excess MSR 0.00%   0.00%    
Excess MSRs | Non-Agency | Nationstar | Original and Recaptured Pools | Minimum          
Investment [Line Items]          
Interest in Excess MSR 0.00%   0.00%    
Excess MSRs | Non-Agency | Nationstar | Original and Recaptured Pools | Maximum          
Investment [Line Items]          
Interest in Excess MSR 33.30%   33.30%    
Excess MSRs | Non-Agency | Nationstar | Recapture Agreements | Minimum          
Investment [Line Items]          
Interest in Excess MSR 0.00%   0.00%    
Excess MSRs | Non-Agency | Nationstar | Recapture Agreements | Maximum          
Investment [Line Items]          
Interest in Excess MSR 33.30%   33.30%    
Excess MSRs | Non-Agency | Nationstar | Ocwen Serviced Pools          
Investment [Line Items]          
Interest in Excess MSR 0.00%   0.00%