Guarantees Mortgage Loans Repurchase Reserve Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Guarantees [Abstract]
Reserve For Mortgage Loan Repurchase Losses	$ 26	$ 39	$ 40	$ 57
Mortgage Repurchase Reserve, Provision for Mortgage Loan Repurchase Losses	(9)	0	(17)
Charge Offs For Mortgage Loan Repurchase Losses	$ 4	$ 1	$ 0