Credit Quality And Allowance For Credit Losses (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Retail loans secured by residential real estate in process of foreclosure	$ 0		$ 0		$ 0
Commitments to lend additional funds to TDR borrowers	44		$ 44		$ 31
Principal Deferrals
Days past due defined as subsequent default			90 days	90 days
Balance	137	$ 151	$ 137	$ 151
Subsequent default during period	0	0	$ 0
Interest Rate Reductions
Days past due defined as subsequent default			90 days	90 days
Balance	2	3	$ 2	$ 3
Subsequent default during period	0	0	$ 0	$ 0
AB Note Restructures
Days past due defined as subsequent default			90 days	90 days
Balance	0	68	$ 0	$ 68
Subsequent default during period	$ 0	$ 0	$ 0	$ 0