Asset Quality (Analysis of Loan Portfolio) (Details) - USD ($) $ in Millions	Sep. 30, 2018		Dec. 31, 2017		Sep. 30, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 223,053	[1]	$ 220,458	[1]	$ 221,109
% of 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 [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 217,652		$ 214,480
% of Loans	97.58%		97.29%
30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 551		$ 545
% of Loans	0.25%		0.25%
60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 258		$ 238
% of Loans	0.12%		0.11%
90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 619		$ 737
% of Loans	0.28%		0.33%
Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 1,428		$ 1,520
% of Loans	0.64%		0.69%
Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 1,694		$ 1,865
% of Loans	0.76%		0.85%
Fair Value Option Nonaccrual Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 177		$ 197
% of Loans	0.08%		0.09%
Purchased Impaired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 2,102		$ 2,396
% of Loans	0.94%		1.08%
Total commercial lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 149,448		$ 147,439		148,527
Total commercial lending [Member] | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	148,837		146,729
Total commercial lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	97		89
Total commercial lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	54		28
Total commercial lending [Member] | 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	67		39
Total commercial lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	218		156
Total commercial lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	393		554
Total consumer lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	73,605		73,019		$ 72,582
Total consumer lending [Member] | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	68,815		67,751
Total consumer lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	454		456
Total consumer lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	204		210
Total consumer lending [Member] | 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	552		698
Total consumer lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,210		1,364
Total consumer lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,301		1,311
Total consumer lending [Member] | Fair Value Option Nonaccrual Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	177		197
Total consumer lending [Member] | Purchased Impaired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	2,102		2,396
Commercial [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	113,671		110,527
Commercial [Member] | Total commercial lending [Member] | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	113,189		109,989
Commercial [Member] | Total commercial lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	60		45
Commercial [Member] | Total commercial lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	35		25
Commercial [Member] | Total commercial lending [Member] | 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	67		39
Commercial [Member] | Total commercial lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	162		109
Commercial [Member] | Total commercial lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	320		429
Commercial Real Estate [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	28,563		28,978
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	28,484		28,826
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		27
Commercial Real Estate [Member] | Total commercial lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	3		2
Commercial Real Estate [Member] | Total commercial lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	11		29
Commercial Real Estate [Member] | Total commercial lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	68		123
Equipment Lease Financing [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	7,214		7,934
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	7,164		7,914
Equipment Lease Financing [Member] | Total commercial lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	29		17
Equipment Lease Financing [Member] | Total commercial lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	16		1
Equipment Lease Financing [Member] | Total commercial lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	45		18
Equipment Lease Financing [Member] | Total commercial lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	5		2
Home Equity [Member] | Total consumer lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	26,628		28,364
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	24,967		26,561
Home Equity [Member] | Total consumer lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	77		78
Home Equity [Member] | Total consumer lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	30		26
Home Equity [Member] | Total consumer lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	107		104
Home Equity [Member] | Total consumer lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	828		818
Home Equity [Member] | Total consumer lending [Member] | Purchased Impaired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	726		881
Residential Real Estate [Member] | Total consumer lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	18,203		17,212
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	15,733		14,389
Residential Real Estate [Member] | Total consumer lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	130		151
Residential Real Estate [Member] | Total consumer lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	67		74
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	357		486
Residential Real Estate [Member] | Total consumer lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	554		711
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	363		400
Residential Real Estate [Member] | Total consumer lending [Member] | Fair Value Option Nonaccrual Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	177		197
Residential Real Estate [Member] | Total consumer lending [Member] | Purchased Impaired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,376		1,515
Credit Card [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	5,979		5,699
Credit Card [Member] | Total consumer lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	5,979		5,699
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	5,852		5,579
Credit Card [Member] | Total consumer lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	45		43
Credit Card [Member] | Total consumer lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	28		26
Credit Card [Member] | Total consumer lending [Member] | 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	48		45
Credit Card [Member] | Total consumer lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	121		114
Credit Card [Member] | Total consumer lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	6		6
Automobile [Member] | Total consumer lending [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	14,309		12,880
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	14,077		12,697
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	104		79
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	25		20
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	8		8
Automobile [Member] | Total consumer lending [Member] | Total Past Due [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	137		107
Automobile [Member] | Total consumer lending [Member] | Nonperforming Loans [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	95		76
Education and Other [Member] | Total consumer lending [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	8,486		8,864
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	8,186		8,525
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	98		105
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	54		64
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	139		159
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	291		328
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	200		300
Education and Other [Member] | Total consumer lending [Member] | Nonperforming Loans [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 9		$ 11

[1] Our consolidated assets included the following for which we have elected the fair value option: Loans held for sale of $1.0 billion, Loans of $.8 billion and Other assets of $.2 billion at September 30, 2018 and Loans held for sale of $1.7 billion, Loans of $.9 billion and Other assets of $.3 billion at December 31, 2017.