Loans And Allowance For Credit Losses (Summary Of Changes In The Allowance For Credit Losses) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan and Lease Losses, Provision for Loss, Gross	$ (5)	$ (19)	$ (35)	$ (95)
Allowance for Loan and Lease Losses, Write-offs	(25)	(54)	(117)	(159)
Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	544	608	567	606
Allowance for Loan and Lease Losses, Adjustments, Other	(8)	(30)	(61)	(104)
Balance at end of period	59	62	59	62
Allowance for loan losses	544	608	567	606	$ 541	$ 544	$ 567	$ 597	$ 608	$ 606
Reserve for unfunded lending commitments	59	62	59	62	59	63	65	62	65	75
Total allowance for credit losses					600			659
Allowance for Loan and Lease Losses, Recoveries of Bad Debts	17	24	56	55
Provision for Unfunded Lending Commitments	(4)	(3)	(6)	(13)
Balance at end of period	541	597	541	597
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan and Lease Losses, Provision for Loss, Gross	4	(22)	(27)	(93)
Allowance for Loan and Lease Losses, Write-offs	(16)	(48)	(98)	(137)
Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	393	457	420	454
Allowance for Loan and Lease Losses, Adjustments, Other	(4)	(33)	(62)	(101)
Balance at end of period	49	52	49	52
Allowance for loan losses	393	457	420	454	385	393	420	446	457	454
Reserve for unfunded lending commitments	49	52	49	52	49	53	54	52	54	58
Total allowance for credit losses					434			498
Allowance for Loan and Lease Losses, Recoveries of Bad Debts	12	15	36	36
Provision for Unfunded Lending Commitments	(4)	(2)	(5)	(6)
Balance at end of period	385	446	385	446
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan and Lease Losses, Provision for Loss, Gross	7	6	15	(5)
Allowance for Loan and Lease Losses, Write-offs	(4)	(1)	(6)	(10)
Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	116	121	116	114
Allowance for Loan and Lease Losses, Adjustments, Other	(2)	6	6	2
Balance at end of period	10	10	10	10
Allowance for loan losses	116	121	116	114	107	116	116	121	121	114
Reserve for unfunded lending commitments	10	10	10	10	10	10	11	10	11	16
Total allowance for credit losses					117			131
Allowance for Loan and Lease Losses, Recoveries of Bad Debts	2	7	12	12
Provision for Unfunded Lending Commitments	0	(1)	(1)	(6)
Balance at end of period	107	121	107	121
Consumer Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan and Lease Losses, Provision for Loss, Gross	(16)	(3)	(23)	3
Allowance for Loan and Lease Losses, Write-offs	(5)	(5)	(13)	(12)
Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	35	30	31	38
Allowance for Loan and Lease Losses, Adjustments, Other	(2)	(3)	(5)	(5)
Balance at end of period	0	0	0	0
Allowance for loan losses	35	30	31	38	49	35	31	30	30	38
Reserve for unfunded lending commitments	0	0	0	0	0	$ 0	$ 0	0	$ 0	$ 1
Total allowance for credit losses					$ 49			$ 30
Allowance for Loan and Lease Losses, Recoveries of Bad Debts	3	2	8	7
Provision for Unfunded Lending Commitments	0	0	0	(1)
Balance at end of period	$ 49	$ 30	$ 49	$ 30