Credit Quality And Allowance For Credit Losses (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Retail loans secured by residential real estate in process of foreclosure	$ 0		$ 0		$ 1
Commitments to lend additional funds to TDR borrowers	37		$ 37		$ 6
Interest Rate Reductions
Days past due defined as subsequent default			90 days	90 days
Balance	4	$ 2	$ 4	$ 2
Subsequent default during period	0	0	$ 0	0
AB Note Restructures
Days past due defined as subsequent default			90 days
Balance	52		$ 52
Subsequent default during period	$ 0	$ 0	$ 0	$ 0