Guarantees Mortgage Loans Repurchase Reserve Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Guarantees [Abstract]
Reserve For Mortgage Loan Repurchase Losses	$ 22	$ 36	$ 22	$ 36	$ 23	$ 26	$ 36	$ 39
Mortgage Repurchase Reserve, Provision for Mortgage Loan Repurchase Losses	(1)	1	(4)	(2)
Charge Offs For Mortgage Loan Repurchase Losses	$ 0	$ (1)	$ 0	$ (1)