Loans And Allowance For Credit Losses (Summary Of Changes In The Allowance For Credit Losses) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Current Fiscal Year End Date									--12-31
Allowance for Credit Losses [Roll Forward]
Balance at beginning of period				$ 567				$ 606	$ 567	$ 606
Provision for loan losses	$ (11)	$ 5	$ 7	23	$ (3)	$ 19	$ 35	42	24	93	$ 40
Gross loan and lease charge-offs									(144)	(198)
Recoveries									71	66
Net loan and lease charge-offs									(73)	(132)
Balance at end of period	518				567				518	567	606
Balance at beginning of period				65				75	65	75
Provision charged (credited) to earnings									(7)	(10)	(6)
Balance at end of period	58				65				58	65	75
Allowance for loan losses	518			567	567			606	567	606	606	$ 518	$ 567
Reserve for unfunded lending commitments	58			65	65			75	65	75	75	58	65
Total allowance for credit losses												576	632
Commercial [Member]
Allowance for Credit Losses [Roll Forward]
Balance at beginning of period				420				454	420	454
Provision for loan losses									23	93
Gross loan and lease charge-offs									(118)	(170)
Recoveries									46	43
Net loan and lease charge-offs									(72)	(127)
Balance at end of period	371				420				371	420	454
Balance at beginning of period				54				58	54	58
Provision charged (credited) to earnings									(6)	(4)
Balance at end of period	48				54				48	54	58
Allowance for loan losses	371			420	420			454	420	454	454	371	420
Reserve for unfunded lending commitments	48			54	54			58	54	58	58	48	54
Total allowance for credit losses												419	474
Commercial Real Estate [Member]
Allowance for Credit Losses [Roll Forward]
Balance at beginning of period				116				114	116	114
Provision for loan losses									(18)	0
Gross loan and lease charge-offs									(9)	(12)
Recoveries									14	14
Net loan and lease charge-offs									5	2
Balance at end of period	103				116				103	116	114
Balance at beginning of period				11				16	11	16
Provision charged (credited) to earnings									(1)	(5)
Balance at end of period	10				11				10	11	16
Allowance for loan losses	103			116	116			114	116	114	114	103	116
Reserve for unfunded lending commitments	10			11	11			16	11	16	16	10	11
Total allowance for credit losses												113	127
Consumer [Member]
Allowance for Credit Losses [Roll Forward]
Balance at beginning of period				31				38	31	38
Provision for loan losses									19	0
Gross loan and lease charge-offs									(17)	(16)
Recoveries									11	9
Net loan and lease charge-offs									(6)	(7)
Balance at end of period	44				31				44	31	38
Balance at beginning of period				0				1	0	1
Provision charged (credited) to earnings									0	(1)
Balance at end of period	0				0				0	0	1
Allowance for loan losses	44			31	31			38	31	38	38	44	31
Reserve for unfunded lending commitments	$ 0			$ 0	$ 0			$ 1	$ 0	$ 1	$ 1	0	0
Total allowance for credit losses												$ 44	$ 31