Credit Quality And Allowance For Credit Losses (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Retail loans secured by residential real estate in process of foreclosure	$ 0	$ 0
Commitments to lend additional funds to TDR borrowers	$ 31	$ 24
Interest rate reductions
Days past due defined as subsequent default	90 days	90 days
Subsequent default during period	$ 0	$ 0
AB Note Restructures
Days past due defined as subsequent default	90 days	90 days
Subsequent default during period	$ 0	$ 0