Variable Interest Entities - Five Largest Geographic Concentrations of Residential Loans (Details) - Variable Interest Entity, Primary Beneficiary - Residential Loans Held For Investment - Geographic Concentration Risk - Residential Mortgage	9 Months Ended
	Sep. 30, 2015
Concentration Risk
Concentration risk percentage	100.00%
California
Concentration Risk
Concentration risk percentage	53.10%
New York
Concentration Risk
Concentration risk percentage	7.60%
Massachusetts
Concentration Risk
Concentration risk percentage	5.90%
Illinois
Concentration Risk
Concentration risk percentage	3.60%
Other states (none greater than 3%)
Concentration Risk
Concentration risk percentage	29.80%
Other states (none greater than 3%) | Maximum
Concentration Risk
Concentration risk percentage per other state	3.00%