Guarantees Repurchased Mortgage Loan (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Repurchased mortgage loans, carrying value	$ 270	$ 272
Performing Financial Instruments [Member] | Loans Held For Investment [Member]
Repurchased mortgage loans, carrying value	253	255
Nonperforming Financing Receivable [Member] | Loans Held For Investment [Member]
Repurchased mortgage loans, carrying value	$ 17	$ 17