Guarantees Repurchased Mortgage Loan (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Document Period End Date	Sep. 30, 2015
Repurchased mortgage loans, carrying value	$ 277	$ 312
Performing Financial Instruments [Member] | Loans Held For Investment [Member]
Repurchased mortgage loans, carrying value	262	271
Nonperforming Financing Receivable [Member] | Loans Held For Investment [Member]
Repurchased mortgage loans, carrying value	15	29
Nonperforming Financing Receivable [Member] | Residential Mortgage, Loans Held For Sale [Member]
Repurchased mortgage loans, carrying value	$ 0	$ 12