Guarantees Repurchased Mortgage Loan (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Repurchased mortgage loans, carrying value	$ 272	$ 312
Performing Financial Instruments [Member] | Loans Held For Investment [Member]
Repurchased mortgage loans, carrying value	255	271
Nonperforming Financing Receivable [Member] | Loans Held For Investment [Member]
Repurchased mortgage loans, carrying value	17	29
Nonperforming Financing Receivable [Member] | Residential Mortgage, Loans Held For Sale [Member]
Repurchased mortgage loans, carrying value	$ 0	$ 12