Guarantees Mortgage Loans Repurchase Reserve Rollforward (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2014
Guarantees [Abstract]
Reserve For Mortgage Loan Repurchase Losses	$ 55	$ 82	$ 57	$ 85
Mortgage Repurchase Reserve, Provision for Mortgage Loan Repurchase Losses	(2)	(2)
Charge Offs For Mortgage Loan Repurchase Losses	$ 0	$ 1