Guarantees Mortgage Loans Repurchase Reserve Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Guarantees [Abstract]
Reserve For Mortgage Loan Repurchase Losses	$ 40	$ 57	$ 85	$ 78
Mortgage Repurchase Reserve, Provision for Mortgage Loan Repurchase Losses	(17)	(12)	12
Charge Offs For Mortgage Loan Repurchase Losses	$ 0	$ (16)	$ (5)