Credit Quality And Allowance For Credit Losses (Narrative) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Retail loans secured by residential real estate in process of foreclosure		$ 0		$ 0
Commitments to lend additional funds to TDR borrowers		21		31
Foreclosed property	[1]	5		5
Principal Deferrals
Days past due defined as subsequent default			90 days
Balance		131	$ 152
Subsequent default during period		$ 0	$ 0
Interest Rate Reductions
Days past due defined as subsequent default		90 days	90 days
Balance		$ 17	$ 1
Subsequent default during period		$ 0	$ 0
AB Note Restructures
Days past due defined as subsequent default		90 days	90 days
Balance		$ 20	$ 48
Subsequent default during period		0	$ 0
Residential Real Estate
Foreclosed property		$ 4		$ 4

[1] Included $4 million of foreclosed residential real estate properties at both March 31, 2018 and December 31, 2017.