Credit Quality And Allowance For Credit Losses (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Retail loans secured by residential real estate in process of foreclosure	$ 0	$ 1
Commitments to lend additional funds to TDR borrowers	3	20
Principal deferrals
Subsequent default during period	$ 12	$ 0
AB Note Restructures
Days past due defined as subsequent default	90 days	90 days
Subsequent default during period	$ 0	$ 0
Interest Rate Reductions
Days past due defined as subsequent default	90 days	90 days
Subsequent default during period	$ 0	$ 0