Asset Quality (Analysis of Loan Portfolio) (Details) - USD ($) $ in Millions	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	$ 226,245	[1]	$ 220,458	[1]	$ 210,833
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		$ 1,200
Current or Less Than 30 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	$ 220,867		$ 214,480
Percentage Of Total Loans	97.62%		97.29%
30-59 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	$ 585		$ 545
Percentage Of Total Loans	0.26%		0.25%
60-89 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	$ 271		$ 238
Percentage Of Total Loans	0.12%		0.11%
90 Days or More Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	$ 629		$ 737
Percentage Of Total Loans	0.28%		0.33%
Total Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	$ 1,485		$ 1,520
Percentage Of Total Loans	0.66%		0.69%
Nonperforming Loans
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	$ 1,694		$ 1,865
Percentage Of Total Loans	0.75%		0.85%
Fair Value Option Nonaccrual Loans
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	$ 182		$ 197
Percentage Of Total Loans	0.08%		0.09%
Purchased Impaired Loans
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	$ 2,017		$ 2,396
Percentage Of Total Loans	0.89%		1.08%
Total commercial lending
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	$ 152,282		$ 147,439		137,955
Total commercial lending | Current or Less Than 30 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	151,585		146,729
Total commercial lending | 30-59 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	144		89
Total commercial lending | 60-89 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	69		28
Total commercial lending | 90 Days or More Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	52		39
Total commercial lending | Total Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	265		156
Total commercial lending | Nonperforming Loans
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	432		554
Total consumer lending
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	73,963		73,019		$ 72,878
Total consumer lending | Current or Less Than 30 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	69,282		67,751
Total consumer lending | 30-59 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	441		456
Total consumer lending | 60-89 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	202		210
Total consumer lending | 90 Days or More Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	577		698
Total consumer lending | Total Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	1,220		1,364
Total consumer lending | Nonperforming Loans
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	1,262		1,311
Total consumer lending | Fair Value Option Nonaccrual Loans
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	182		197
Total consumer lending | Purchased Impaired Loans
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	2,017		2,396
Commercial | Total commercial lending
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	116,834		110,527
Commercial | Total commercial lending | Current or Less Than 30 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	116,300		109,989
Commercial | Total commercial lending | 30-59 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	82		45
Commercial | Total commercial lending | 60-89 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	54		25
Commercial | Total commercial lending | 90 Days or More Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	52		39
Commercial | Total commercial lending | Total Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	188		109
Commercial | Total commercial lending | Nonperforming Loans
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	346		429
Commercial Real Estate | Total commercial lending
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	28,140		28,978
Commercial Real Estate | Total commercial lending | Current or Less Than 30 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	28,056		28,826
Commercial Real Estate | Total commercial lending | 30-59 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	6		27
Commercial Real Estate | Total commercial lending | 60-89 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	3		2
Commercial Real Estate | Total commercial lending | Total Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	9		29
Commercial Real Estate | Total commercial lending | Nonperforming Loans
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	75		123
Equipment Lease Financing | Total commercial lending
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	7,308		7,934
Equipment Lease Financing | Total commercial lending | Current or Less Than 30 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	7,229		7,914
Equipment Lease Financing | Total commercial lending | 30-59 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	56		17
Equipment Lease Financing | Total commercial lending | 60-89 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	12		1
Equipment Lease Financing | Total commercial lending | Total Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	68		18
Equipment Lease Financing | Total commercial lending | Nonperforming Loans
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	11		2
Home Equity
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	26,123		28,364
Home Equity | Government Insured or Guaranteed Loans
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans
Home Equity | Total consumer lending
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	26,123		28,364
Home Equity | Total consumer lending | Current or Less Than 30 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	24,556		26,561
Home Equity | Total consumer lending | 30-59 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	66		78
Home Equity | Total consumer lending | 60-89 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	25		26
Home Equity | Total consumer lending | Total Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	91		104
Home Equity | Total consumer lending | Nonperforming Loans
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	797		818
Home Equity | Total consumer lending | Purchased Impaired Loans
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	679		881
Residential Real Estate
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	18,657		17,212
Residential Real Estate | Government Insured or Guaranteed Loans
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	685		806
Residential Real Estate | Total consumer lending
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	18,657		17,212
Residential Real Estate | Total consumer lending | Current or Less Than 30 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	16,216		14,389
Residential Real Estate | Total consumer lending | 30-59 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	135		151
Residential Real Estate | Total consumer lending | 60-89 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	73		74
Residential Real Estate | Total consumer lending | 90 Days or More Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	363		486
Residential Real Estate | Total consumer lending | Total Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	571		711
Residential Real Estate | Total consumer lending | Total Past Due | Government Insured or Guaranteed Loans
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	500		600
Residential Real Estate | Total consumer lending | Nonperforming Loans
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	350		400
Residential Real Estate | Total consumer lending | Fair Value Option Nonaccrual Loans
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	182		197
Residential Real Estate | Total consumer lending | Purchased Impaired Loans
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	1,338		1,515
Automobile | Total consumer lending
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	14,419		12,880
Automobile | Total consumer lending | Current or Less Than 30 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	14,165		12,697
Automobile | Total consumer lending | 30-59 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	113		79
Automobile | Total consumer lending | 60-89 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	29		20
Automobile | Total consumer lending | 90 Days or More Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	12		8
Automobile | Total consumer lending | Total Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	154		107
Automobile | Total consumer lending | Nonperforming Loans
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	100		76
Credit Card
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	6,357		5,699
Credit Card | Total consumer lending
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	6,357		5,699
Credit Card | Total consumer lending | Current or Less Than 30 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	6,222		5,579
Credit Card | Total consumer lending | 30-59 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	46		43
Credit Card | Total consumer lending | 60-89 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	29		26
Credit Card | Total consumer lending | 90 Days or More Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	53		45
Credit Card | Total consumer lending | Total Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	128		114
Credit Card | Total consumer lending | Nonperforming Loans
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	7		6
Education
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	3,822		4,454
Education | Total consumer lending
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	3,822		4,454
Education | Total consumer lending | Current or Less Than 30 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	3,571		4,154
Education | Total consumer lending | 30-59 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	69		90
Education | Total consumer lending | 60-89 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	41		58
Education | Total consumer lending | 90 Days or More Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	141		152
Education | Total consumer lending | Total Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	251		300
Education | Total consumer lending | Total Past Due | Government Insured or Guaranteed Loans
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	200		300
Other Consumer
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	4,585		4,410
Other Consumer | Total consumer lending
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	4,585		4,410
Other Consumer | Total consumer lending | Current or Less Than 30 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	4,552		4,371
Other Consumer | Total consumer lending | 30-59 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	12		15
Other Consumer | Total consumer lending | 60-89 Days Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	5		6
Other Consumer | Total consumer lending | 90 Days or More Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	8		7
Other Consumer | Total consumer lending | Total Past Due
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	25		28
Other Consumer | Total consumer lending | Nonperforming Loans
Financing Receivable. Recorded Investment, Past Due [Line Items]
Total Loans	$ 8		$ 11

[1] Our consolidated assets included the following for which we have elected the fair value option: Loans held for sale of $.9 billion, Loans of $.8 billion, and Other assets of $.2 billion at December 31, 2018 and Loans held for sale of $1.7 billion, Loans of $.9 billion, and Other assets of $.3 billion at December 31, 2017.