Distressed Residential Mortgage Loans - Geographic Concentrations of Credit Risk (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Florida
Concentration Risk [Line Items]
Geographic concentrations	5.10%	0.00%
Georgia
Concentration Risk [Line Items]
Geographic concentrations	6.30%	0.00%
Distressed residential mortgage loans held in securitization trusts (net) | Geographic Concentration Risk | Florida
Concentration Risk [Line Items]
Geographic concentrations	12.20%	12.60%
Distressed residential mortgage loans held in securitization trusts (net) | Geographic Concentration Risk | California
Concentration Risk [Line Items]
Geographic concentrations	8.80%	7.70%
Distressed residential mortgage loans held in securitization trusts (net) | Geographic Concentration Risk | North Carolina
Concentration Risk [Line Items]
Geographic concentrations	7.70%	8.10%
Distressed residential mortgage loans held in securitization trusts (net) | Geographic Concentration Risk | Georgia
Concentration Risk [Line Items]
Geographic concentrations	6.00%	6.10%
Distressed residential mortgage loans held in securitization trusts (net) | Geographic Concentration Risk | New York
Concentration Risk [Line Items]
Geographic concentrations	5.40%	5.20%
Distressed residential mortgage loans held in securitization trusts (net) | Geographic Concentration Risk | Maryland
Concentration Risk [Line Items]
Geographic concentrations	5.20%	5.40%