Asset Quality (Analysis of Loan Portfolio) (Details) - USD ($) $ in Millions	Mar. 31, 2018		Dec. 31, 2017		Mar. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 221,614	[1]	$ 220,458	[1]	$ 212,826
% 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	$ 215,880		$ 214,480
% of Loans	97.41%		97.29%
30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 527		$ 545
% of Loans	0.24%		0.25%
60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 234		$ 238
% of Loans	0.11%		0.11%
90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 628		$ 737
% of Loans	0.28%		0.33%
Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 1,389		$ 1,520
% of Loans	0.63%		0.69%
Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 1,842		$ 1,865
% of Loans	0.83%		0.85%
Fair Value Option Nonaccrual Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 189		$ 197
% of Loans	0.09%		0.09%
Purchased Impaired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 2,314		$ 2,396
% of Loans	1.04%		1.08%
Total commercial lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 148,945		$ 147,439		140,662
Total commercial lending [Member] | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	148,228		146,729
Total commercial lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	92		89
Total commercial lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	35		28
Total commercial lending [Member] | 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	53		39
Total commercial lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	180		156
Total commercial lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	537		554
Total consumer lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	72,669		73,019		$ 72,164
Total consumer lending [Member] | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	67,652		67,751
Total consumer lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	435		456
Total consumer lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	199		210
Total consumer lending [Member] | 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	575		698
Total consumer lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,209		1,364
Total consumer lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,305		1,311
Total consumer lending [Member] | Fair Value Option Nonaccrual Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	189		197
Total consumer lending [Member] | Purchased Impaired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	2,314		2,396
Commercial Loan [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	112,308		110,527
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	111,754		109,989
Commercial Loan [Member] | Total commercial lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	53		45
Commercial Loan [Member] | Total commercial lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	22		25
Commercial Loan [Member] | Total commercial lending [Member] | 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	53		39
Commercial Loan [Member] | Total commercial lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	128		109
Commercial Loan [Member] | Total commercial lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	426		429
Commercial Real Estate [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	28,835		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	28,695		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	21		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	12		2
Commercial Real Estate [Member] | Total commercial lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	33		29
Commercial Real Estate [Member] | Total commercial lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	107		123
Equipment Lease Financing [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	7,802		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	7,779		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	18		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	1		1
Equipment Lease Financing [Member] | Total commercial lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	19		18
Equipment Lease Financing [Member] | Total commercial lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	4		2
Home Equity [Member] | Total consumer lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	27,699		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	25,919		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	94		78
Home Equity [Member] | Total consumer lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	31		26
Home Equity [Member] | Total consumer lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	125		104
Home Equity [Member] | Total consumer lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	820		818
Home Equity [Member] | Total consumer lending [Member] | Purchased Impaired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	835		881
Residential Real Estate [Member] | Total consumer lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	17,456		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	14,824		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	70		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	373		486
Residential Real Estate [Member] | Total consumer lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	573		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	391		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	189		197
Residential Real Estate [Member] | Total consumer lending [Member] | Purchased Impaired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,479		1,515
Credit Card [Member] | Total consumer lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	5,657		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	5,540		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	40		43
Credit Card [Member] | Total consumer lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	26		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	45		45
Credit Card [Member] | Total consumer lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	111		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	13,295		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	13,112		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	77		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	18		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	9		8
Automobile [Member] | Total consumer lending [Member] | Total Past Due [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	104		107
Automobile [Member] | Total consumer lending [Member] | Nonperforming Loans [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	79		76
Education and Other [Member] | Total consumer lending [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	8,562		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	8,257		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	94		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	148		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	296		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	300		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 $.9 billion, Loans of $.8 billion and Other assets of $.3 billion at March 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.