Commercial Mortgage Residual Interests (Schedule of Key Assumptions Used in Determining the Value of the Residuals) (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Mortgage Loans On Real Estate [Line Items]
Discount rate	20.00%	20.00%
Loss severity of loans in foreclosure	20.00%	20.00%
LIBOR	Forward 3-month curve	Forward 3-month curve
Prime	Forward curve	Forward curve
Minimum
Mortgage Loans On Real Estate [Line Items]
Average Life Equivalent CPR Speeds Range	0.87%	0.87%
Foreclosures Frequency Curve Default Model	0.72%	0.70%
Maximum
Mortgage Loans On Real Estate [Line Items]
Average Life Equivalent CPR Speeds Range	21.73%	26.30%
Foreclosures Frequency Curve Default Model	1.57%	2.45%