Asset Quality (Analysis of Loan Portfolio) (Details) - USD ($) $ in Millions	Sep. 30, 2017		Dec. 31, 2016		Sep. 30, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 221,109	[1]	$ 210,833	[1]	$ 210,446
Percentage Of Total Loans	100.00%		100.00%
Unearned income, net deferred loan fees, unamortized discounts and premiums, and purchase discounts and premiums	$ 1,200		$ 1,300
Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 215,060		$ 203,938
Percentage Of Total Loans	97.26%		96.73%
30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 486		$ 562
Percentage Of Total Loans	0.22%		0.27%
60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 255		$ 232
Percentage Of Total Loans	0.12%		0.11%
90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 678		$ 782
Percentage Of Total Loans	0.31%		0.37%
Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 1,419		$ 1,576
Percentage Of Total Loans	0.64%		0.75%
Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 1,873		$ 2,144
Percentage Of Total Loans	0.85%		1.02%
Fair Value Option Nonaccrual Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 200		$ 219
Percentage Of Total Loans	0.09%		0.10%
Purchased Impaired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 2,557		$ 2,956
Percentage Of Total Loans	1.16%		1.40%
Total commercial lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 148,527		$ 137,955		138,163
Total commercial lending [Member] | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	147,772		137,014
Total commercial lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	56		115
Total commercial lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	44		23
Total commercial lending [Member] | 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	47		39
Total commercial lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	147		177
Total commercial lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	550		655
Total commercial lending [Member] | Purchased Impaired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	58		109
Total consumer lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	72,582		72,878		$ 72,283
Total consumer lending [Member] | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	67,288		66,924
Total consumer lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	430		447
Total consumer lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	211		209
Total consumer lending [Member] | 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	631		743
Total consumer lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,272		1,399
Total consumer lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,323		1,489
Total consumer lending [Member] | Fair Value Option Nonaccrual Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	200		219
Total consumer lending [Member] | Purchased Impaired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	2,499		2,847
Commercial Loan [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	111,317		101,364
Commercial Loan [Member] | Total commercial lending [Member] | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	110,765		100,710
Commercial Loan [Member] | Total commercial lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	44		81
Commercial Loan [Member] | Total commercial lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	28		20
Commercial Loan [Member] | Total commercial lending [Member] | 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	47		39
Commercial Loan [Member] | Total commercial lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	119		140
Commercial Loan [Member] | Total commercial lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	419		496
Commercial Loan [Member] | Total commercial lending [Member] | Purchased Impaired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	14		18
Commercial Real Estate [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	29,516		29,010
Commercial Real Estate [Member] | Total commercial lending [Member] | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	29,323		28,769
Commercial Real Estate [Member] | Total commercial lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	8		5
Commercial Real Estate [Member] | Total commercial lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	13		2
Commercial Real Estate [Member] | Total commercial lending [Member] | 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans
Commercial Real Estate [Member] | Total commercial lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	21		7
Commercial Real Estate [Member] | Total commercial lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	128		143
Commercial Real Estate [Member] | Total commercial lending [Member] | Purchased Impaired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	44		91
Equipment Lease Financing [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	7,694		7,581
Equipment Lease Financing [Member] | Total commercial lending [Member] | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	7,684		7,535
Equipment Lease Financing [Member] | Total commercial lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	4		29
Equipment Lease Financing [Member] | Total commercial lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	3		1
Equipment Lease Financing [Member] | Total commercial lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	7		30
Equipment Lease Financing [Member] | Total commercial lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	3		16
Home Equity [Member] | Total consumer lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	28,811		29,949
Home Equity [Member] | Total consumer lending [Member] | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	26,959		27,820
Home Equity [Member] | Total consumer lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	74		64
Home Equity [Member] | Total consumer lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	31		30
Home Equity [Member] | Total consumer lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	105		94
Home Equity [Member] | Total consumer lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	814		914
Home Equity [Member] | Total consumer lending [Member] | Purchased Impaired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	933		1,121
Residential Real Estate [Member] | Total consumer lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	16,601		15,598
Residential Real Estate [Member] | Total consumer lending [Member] | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	13,788		12,425
Residential Real Estate [Member] | Total consumer lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	135		159
Residential Real Estate [Member] | Total consumer lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	71		68
Residential Real Estate [Member] | Total consumer lending [Member] | 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	418		500
Residential Real Estate [Member] | Total consumer lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	624		727
Residential Real Estate [Member] | Total consumer lending [Member] | Total Past Due [Member] | Government Insured or Guaranteed Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	500		600
Residential Real Estate [Member] | Total consumer lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	423		501
Residential Real Estate [Member] | Total consumer lending [Member] | Fair Value Option Nonaccrual Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	200		219
Residential Real Estate [Member] | Total consumer lending [Member] | Purchased Impaired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,566		1,726
Credit Card [Member] | Total consumer lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	5,375		5,282
Credit Card [Member] | Total consumer lending [Member] | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	5,267		5,187
Credit Card [Member] | Total consumer lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	40		33
Credit Card [Member] | Total consumer lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	25		21
Credit Card [Member] | Total consumer lending [Member] | 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	38		37
Credit Card [Member] | Total consumer lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	103		91
Credit Card [Member] | Total consumer lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	5		4
Automobile [Member] | Total consumer lending [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	12,743		12,380
Automobile [Member] | Total consumer lending [Member] | Current or Less Than 30 Days Past Due [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	12,580		12,257
Automobile [Member] | Total consumer lending [Member] | 30-59 Days Past Due [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	71		51
Automobile [Member] | Total consumer lending [Member] | 60-89 Days Past Due [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	16		12
Automobile [Member] | Total consumer lending [Member] | 90 Days or More Past Due [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	5		5
Automobile [Member] | Total consumer lending [Member] | Total Past Due [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	92		68
Automobile [Member] | Total consumer lending [Member] | Nonperforming Loans [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	71		55
Education and other [Member] | Total consumer lending [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	9,052		9,669
Education and other [Member] | Total consumer lending [Member] | Current or Less Than 30 Days Past Due [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	8,694		9,235
Education and other [Member] | Total consumer lending [Member] | 30-59 Days Past Due [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	110		140
Education and other [Member] | Total consumer lending [Member] | 60-89 Days Past Due [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	68		78
Education and other [Member] | Total consumer lending [Member] | 90 Days or More Past Due [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	170		201
Education and other [Member] | Total consumer lending [Member] | Total Past Due [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	348		419
Education and other [Member] | Total consumer lending [Member] | Total Past Due [Member] | Government Insured or Guaranteed Loans [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	300		400
Education and other [Member] | Total consumer lending [Member] | Nonperforming Loans [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 10		$ 15

[1] Our consolidated assets included the following for which we have elected the fair value option: Loans held for sale of $1.6 billion, Loans of $.8 billion and Other assets of $.3 billion at September 30, 2017 and Loans held for sale of $2.4 billion, Loans of $.9 billion and Other assets of $.5 billion at December 31, 2016.