Loans And Allowance For Credit Losses (Summary Of Changes In The Allowance For Credit Losses) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan and Lease Losses, Provision for Loss, Gross	$ (7)	$ (35)	$ (30)	$ (77)
Allowance for Loan and Lease Losses, Write-offs	(35)	(58)	(92)	(106)
Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	544	612	567	606
Allowance for Loan and Lease Losses, Adjustments, Other	(7)	(39)	(53)	(75)
Balance at end of period	63	65	63	65
Allowance for loan losses	544	612	567	606	$ 544	$ 544	$ 567	$ 608	$ 612	$ 606
Reserve for unfunded lending commitments	63	65	63	65	63	60	65	65	69	75
Total allowance for credit losses					607			673
Allowance for Loan and Lease Losses, Recoveries of Bad Debts	28	19	39	31
Provision for Unfunded Lending Commitments	3	(4)	(2)	(10)
Balance at end of period	544	608	544	608
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan and Lease Losses, Provision for Loss, Gross	(9)	(25)	(32)	(71)
Allowance for Loan and Lease Losses, Write-offs	(31)	(47)	(82)	(90)
Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	397	464	420	454
Allowance for Loan and Lease Losses, Adjustments, Other	(13)	(33)	(59)	(69)
Balance at end of period	54	54	54	54
Allowance for loan losses	397	464	420	454	393	397	420	456	464	454
Reserve for unfunded lending commitments	54	54	54	54	54	51	54	54	56	58
Total allowance for credit losses					447			510
Allowance for Loan and Lease Losses, Recoveries of Bad Debts	18	14	23	21
Provision for Unfunded Lending Commitments	3	(2)	0	(4)
Balance at end of period	393	456	393	456
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan and Lease Losses, Provision for Loss, Gross	5	(10)	9	(12)
Allowance for Loan and Lease Losses, Write-offs	(1)	(8)	(2)	(9)
Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	114	118	116	114
Allowance for Loan and Lease Losses, Adjustments, Other	7	(6)	9	(4)
Balance at end of period	9	11	9	11
Allowance for loan losses	114	118	116	114	116	114	116	122	118	114
Reserve for unfunded lending commitments	9	11	9	11	9	9	11	11	13	16
Total allowance for credit losses					125			133
Allowance for Loan and Lease Losses, Recoveries of Bad Debts	8	2	11	5
Provision for Unfunded Lending Commitments	0	(2)	(2)	(5)
Balance at end of period	116	122	116	122
Consumer Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan and Lease Losses, Provision for Loss, Gross	(3)	0	(7)	6
Allowance for Loan and Lease Losses, Write-offs	(3)	(3)	(8)	(7)
Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	33	30	31	38
Allowance for Loan and Lease Losses, Adjustments, Other	(1)	0	(3)	(2)
Balance at end of period	0	0	0	0
Allowance for loan losses	33	30	31	38	35	33	31	30	30	38
Reserve for unfunded lending commitments	0	0	0	0	0	$ 0	$ 0	0	$ 0	$ 1
Total allowance for credit losses					$ 35			$ 30
Allowance for Loan and Lease Losses, Recoveries of Bad Debts	2	3	5	5
Provision for Unfunded Lending Commitments	0	0	0	(1)
Balance at end of period	$ 35	$ 30	$ 35	$ 30