Loans And Allowance For Credit Losses (Summary Of Changes In The Allowance For Credit Losses) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Dec. 31, 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	$ (23)	$ (42)
Allowance for Loan and Lease Losses, Write-offs	(57)	(48)
Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	567	606
Allowance for Loan and Lease Losses, Adjustments, Other	(46)	(36)
Balance at end of period	60	69
Allowance for loan losses	567	606	$ 544	$ 567	$ 612	$ 606
Reserve for unfunded lending commitments	60	69	60	65	69	75
Total allowance for credit losses			604		681
Allowance for Loan and Lease Losses, Recoveries of Bad Debts	11	12
Provision for Unfunded Lending Commitments	(5)	(6)
Balance at end of period	544	612
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan and Lease Losses, Provision for Loss, Gross	(22)	(46)
Allowance for Loan and Lease Losses, Write-offs	(51)	43
Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	420	454
Allowance for Loan and Lease Losses, Adjustments, Other	(45)	(36)
Balance at end of period	50	56
Allowance for loan losses	420	454	397	420	464	454
Reserve for unfunded lending commitments	50	56	50	54	56	58
Total allowance for credit losses			447		520
Allowance for Loan and Lease Losses, Recoveries of Bad Debts	6	7
Provision for Unfunded Lending Commitments	(4)	2
Balance at end of period	397	464
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan and Lease Losses, Provision for Loss, Gross	3	(2)
Allowance for Loan and Lease Losses, Write-offs	(1)	1
Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	116	114
Allowance for Loan and Lease Losses, Adjustments, Other	1	2
Balance at end of period	10	13
Allowance for loan losses	116	114	114	116	118	114
Reserve for unfunded lending commitments	10	13	10	11	13	17
Total allowance for credit losses			124		131
Allowance for Loan and Lease Losses, Recoveries of Bad Debts	2	3
Provision for Unfunded Lending Commitments	(1)	4
Balance at end of period	114	118
Consumer Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan and Lease Losses, Provision for Loss, Gross	(4)	6
Allowance for Loan and Lease Losses, Write-offs	(5)	4
Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	31	38
Allowance for Loan and Lease Losses, Adjustments, Other	(2)	(2)
Balance at end of period	0	0
Allowance for loan losses	31	38	33	31	30	38
Reserve for unfunded lending commitments	0	0	0	$ 0	0	$ 0
Total allowance for credit losses			$ 33		$ 30
Allowance for Loan and Lease Losses, Recoveries of Bad Debts	3	2
Provision for Unfunded Lending Commitments	0	0
Balance at end of period	$ 33	$ 30