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
Mar. 31, 2019
Mar. 31, 2018
Dec. 31, 2018
Investment [Line Items]      
UPB of Underlying Mortgages $ 21,900,000    
Weighted Average Life (Years) 27 days    
Principal investment gain (loss) $ 4,627 $ (45,691)  
Servicer Advance Investments | Servicer Advances      
Investment [Line Items]      
UPB of Underlying Mortgages 38,055,282   $ 40,096,998
Original and Recaptured Pools      
Investment [Line Items]      
Principal investment gain (loss) 1,518 (43,122)  
Recapture Agreements      
Investment [Line Items]      
Principal investment gain (loss) 3,109 $ (2,569)  
Excess MSRs      
Investment [Line Items]      
UPB of Underlying Mortgages $ 103,027,952    
Weighted Average Life (Years) 6 years    
Amortized Cost Basis $ 344,977    
Carrying Value 436,137   447,860
Excess MSRs | Nationstar      
Investment [Line Items]      
Carrying Value 433,752   445,328
Excess MSRs | Agency      
Investment [Line Items]      
UPB of Underlying Mortgages $ 50,945,281    
Weighted Average Life (Years) 6 years    
Amortized Cost Basis $ 207,635    
Carrying Value 248,438   257,387
Excess MSRs | Agency | Original and Recaptured Pools      
Investment [Line Items]      
UPB of Underlying Mortgages $ 50,945,281    
Weighted Average Life (Years) 5 years 6 months    
Amortized Cost Basis $ 193,115    
Carrying Value $ 215,787   226,452
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 2 months 12 days    
Amortized Cost Basis $ 14,520    
Carrying Value $ 32,651   30,935
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 $ 52,082,671    
Weighted Average Life (Years) 5 years 10 months 24 days    
Amortized Cost Basis $ 137,342    
Carrying Value 187,699   190,473
Excess MSRs | Non-Agency | Original and Recaptured Pools      
Investment [Line Items]      
UPB of Underlying Mortgages $ 52,082,671    
Weighted Average Life (Years) 5 years 8 months 12 days    
Amortized Cost Basis $ 133,652    
Carrying Value $ 169,673   172,712
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 8 months 12 days    
Amortized Cost Basis $ 3,690    
Carrying Value $ 18,026   $ 17,761
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 | 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 | 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%