Asset Quality (Analysis of Loan Portfolio) (Details) - USD ($) $ in Millions	Jun. 30, 2019		Dec. 31, 2018		Jun. 30, 2018
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 237,215	[1]	$ 226,245	[1]	$ 222,855
% 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	$ 232,138		$ 220,867
% of Loans	97.86%		97.62%
30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 550		$ 585
% of Loans	0.23%		0.26%
60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 235		$ 271
% of Loans	0.10%		0.12%
90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 524		$ 629
% of Loans	0.22%		0.28%
Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 1,309		$ 1,485
% of Loans	0.55%		0.66%
Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 1,724		$ 1,694
% of Loans	0.73%		0.75%
Fair Value Option Nonaccrual Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 173		$ 182
% of Loans	0.07%		0.08%
Purchased Impaired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 1,871		$ 2,017
% of Loans	0.79%		0.89%
Total commercial lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 161,603		$ 152,282		149,636
Total commercial lending [Member] | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	160,846		151,585
Total commercial lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	121		144
Total commercial lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	37		69
Total commercial lending [Member] | 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	59		52
Total commercial lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	217		265
Total commercial lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	540		432
Total consumer lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	75,612		73,963		$ 73,219
Total consumer lending [Member] | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	71,292		69,282
Total consumer lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	429		441
Total consumer lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	198		202
Total consumer lending [Member] | 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	465		577
Total consumer lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,092		1,220
Total consumer lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,184		1,262
Total consumer lending [Member] | Fair Value Option Nonaccrual Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	173		182
Total consumer lending [Member] | Purchased Impaired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,871		2,017
Commercial [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	125,624		116,834
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	124,986		116,300
Commercial [Member] | Total commercial lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	105		82
Commercial [Member] | Total commercial lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	33		54
Commercial [Member] | Total commercial lending [Member] | 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	59		52
Commercial [Member] | Total commercial lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	197		188
Commercial [Member] | Total commercial lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	441		346
Commercial Real Estate [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	28,570		28,140
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	28,467		28,056
Commercial Real Estate [Member] | Total commercial lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	9		6
Commercial Real Estate [Member] | Total commercial lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1		3
Commercial Real Estate [Member] | Total commercial lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	10		9
Commercial Real Estate [Member] | Total commercial lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	93		75
Equipment Lease Financing [Member] | Total commercial lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	7,409		7,308
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	7,393		7,229
Equipment Lease Financing [Member] | Total commercial lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	7		56
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		12
Equipment Lease Financing [Member] | Total commercial lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	10		68
Equipment Lease Financing [Member] | Total commercial lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	6		11
Home Equity [Member] | Total consumer lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	25,132		26,123
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	23,730		24,556
Home Equity [Member] | Total consumer lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	56		66
Home Equity [Member] | Total consumer lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	20		25
Home Equity [Member] | Total consumer lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	76		91
Home Equity [Member] | Total consumer lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	712		797
Home Equity [Member] | Total consumer lending [Member] | Purchased Impaired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	614		679
Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	20,092		18,657
Residential Real Estate [Member] | Government Insured or Guaranteed Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	593		685
Residential Real Estate [Member] | Total consumer lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	20,092		18,657
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	17,808		16,216
Residential Real Estate [Member] | Total consumer lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	134		135
Residential Real Estate [Member] | Total consumer lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	75		73
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	306		363
Residential Real Estate [Member] | Total consumer lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	515		571
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	400		500
Residential Real Estate [Member] | Total consumer lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	339		350
Residential Real Estate [Member] | Total consumer lending [Member] | Fair Value Option Nonaccrual Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	173		182
Residential Real Estate [Member] | Total consumer lending [Member] | Purchased Impaired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	1,257		1,338
Automobile [Member] | Total consumer lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	15,612		14,419
Automobile [Member] | Total consumer lending [Member] | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	15,338		14,165
Automobile [Member] | Total consumer lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	119		113
Automobile [Member] | Total consumer lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	29		29
Automobile [Member] | Total consumer lending [Member] | 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	8		12
Automobile [Member] | Total consumer lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	156		154
Automobile [Member] | Total consumer lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	118		100
Credit Card [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	6,511		6,357
Credit Card [Member] | Total consumer lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	6,511		6,357
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	6,379		6,222
Credit Card [Member] | Total consumer lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	47		46
Credit Card [Member] | Total consumer lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	29		29
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		53
Credit Card [Member] | Total consumer lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	124		128
Credit Card [Member] | Total consumer lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	8		7
Education [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	3,555		3,822
Education [Member] | Total consumer lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	3,555		3,822
Education [Member] | Total consumer lending [Member] | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	3,364		3,571
Education [Member] | Total consumer lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	60		69
Education [Member] | Total consumer lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	36		41
Education [Member] | Total consumer lending [Member] | 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	95		141
Education [Member] | Total consumer lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	191		251
Education [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	200		200
Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	4,710		4,585
Other Consumer [Member] | Total consumer lending [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	4,710		4,585
Other Consumer [Member] | Total consumer lending [Member] | Current or Less Than 30 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	4,673		4,552
Other Consumer [Member] | Total consumer lending [Member] | 30-59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	13		12
Other Consumer [Member] | Total consumer lending [Member] | 60-89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	9		5
Other Consumer [Member] | Total consumer lending [Member] | 90 Days or More Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	8		8
Other Consumer [Member] | Total consumer lending [Member] | Total Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	30		25
Other Consumer [Member] | Total consumer lending [Member] | Nonperforming Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans	$ 7		$ 8

[1] Our consolidated assets included the following for which we have elected the fair value option: Loans held for sale of $1.1 billion, Loans of $.8 billion and Other assets of $.1 billion at June 30, 2019 and Loans held for sale of $.9 billion, Loans of $.8 billion and Other assets of $.2 billion at December 31, 2018.