Residential Mortgage Loans Held in Securitization Trusts (Net) and Real Estate Owned - Geographic Concentrations of Credit Risk (Details) - Residential Mortgage Loans Held in Securitization Trusts and Real Estate Owned Held in Residential Securitization	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
New York
Concentration Risk [Line Items]
Geographic concentrations	35.60%	36.10%
Massachusetts
Concentration Risk [Line Items]
Geographic concentrations	20.70%	24.00%
New Jersey
Concentration Risk [Line Items]
Geographic concentrations	11.10%	10.90%
Florida
Concentration Risk [Line Items]
Geographic concentrations	7.70%	6.20%
Connecticut
Concentration Risk [Line Items]
Geographic concentrations	6.50%	5.90%