Asset Quality - Aging Analysis of Past Due and Current Loans (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Past Due [Line Items]
Total loans	$ 101,854	$ 101,185
Nonperforming
Financing Receivable, Past Due [Line Items]
Total loans	454	785
Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	76	148
Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	89	93
Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	68	86
Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Total loans	101,167	100,073
Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Total loans	687	1,112
Commercial Loans
Financing Receivable, Past Due [Line Items]
Total loans	70,836	71,980
Accrued interest	113
Commercial Loans | Nonperforming
Financing Receivable, Past Due [Line Items]
Total loans	239	497
Commercial Loans | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total loans	50,525	52,907
Accrued interest	198	241
Commercial Loans | Commercial and industrial | Nonperforming
Financing Receivable, Past Due [Line Items]
Total loans	191	385
Commercial Loans | Commercial mortgage
Financing Receivable, Past Due [Line Items]
Total loans	14,244	12,687
Commercial Loans | Commercial mortgage | Nonperforming
Financing Receivable, Past Due [Line Items]
Total loans	44	104
Commercial Loans | Commercial Real Estate : Construction
Financing Receivable, Past Due [Line Items]
Total loans	1,996	1,987
Commercial Loans | Commercial Real Estate : Construction | Nonperforming
Financing Receivable, Past Due [Line Items]
Total loans	0	0
Commercial Loans | Commercial real estate loans
Financing Receivable, Past Due [Line Items]
Total loans	16,240	14,674
Commercial Loans | Commercial real estate loans | Nonperforming
Financing Receivable, Past Due [Line Items]
Total loans	44	104
Commercial Loans | Commercial lease financing
Financing Receivable, Past Due [Line Items]
Total loans	4,071	4,399
Commercial Loans | Commercial lease financing | Nonperforming
Financing Receivable, Past Due [Line Items]
Total loans	4	8
Commercial Loans | Commercial credit card
Financing Receivable, Past Due [Line Items]
Total loans	139	127
Commercial Loans | Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	35	66
Commercial Loans | Financial Asset, 30 to 59 Days Past Due | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total loans	19	36
Commercial Loans | Financial Asset, 30 to 59 Days Past Due | Commercial mortgage
Financing Receivable, Past Due [Line Items]
Total loans	10	9
Commercial Loans | Financial Asset, 30 to 59 Days Past Due | Commercial Real Estate : Construction
Financing Receivable, Past Due [Line Items]
Total loans	0	0
Commercial Loans | Financial Asset, 30 to 59 Days Past Due | Commercial real estate loans
Financing Receivable, Past Due [Line Items]
Total loans	10	9
Commercial Loans | Financial Asset, 30 to 59 Days Past Due | Commercial lease financing
Financing Receivable, Past Due [Line Items]
Total loans	6	21
Commercial Loans | Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	75	56
Commercial Loans | Financial Asset, 60 to 89 Days Past Due | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total loans	49	50
Commercial Loans | Financial Asset, 60 to 89 Days Past Due | Commercial mortgage
Financing Receivable, Past Due [Line Items]
Total loans	9	5
Commercial Loans | Financial Asset, 60 to 89 Days Past Due | Commercial Real Estate : Construction
Financing Receivable, Past Due [Line Items]
Total loans	17	0
Commercial Loans | Financial Asset, 60 to 89 Days Past Due | Commercial real estate loans
Financing Receivable, Past Due [Line Items]
Total loans	26	5
Commercial Loans | Financial Asset, 60 to 89 Days Past Due | Commercial lease financing
Financing Receivable, Past Due [Line Items]
Total loans	0	1
Commercial Loans | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	48	62
Commercial Loans | Financial Asset, Equal to or Greater than 90 Days Past Due | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total loans	40	40
Commercial Loans | Financial Asset, Equal to or Greater than 90 Days Past Due | Commercial mortgage
Financing Receivable, Past Due [Line Items]
Total loans	7	21
Commercial Loans | Financial Asset, Equal to or Greater than 90 Days Past Due | Commercial Real Estate : Construction
Financing Receivable, Past Due [Line Items]
Total loans	1	1
Commercial Loans | Financial Asset, Equal to or Greater than 90 Days Past Due | Commercial real estate loans
Financing Receivable, Past Due [Line Items]
Total loans	8	22
Commercial Loans | Financial Asset, Equal to or Greater than 90 Days Past Due | Commercial lease financing
Financing Receivable, Past Due [Line Items]
Total loans	0	0
Commercial Loans | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Total loans	70,439	71,299
Commercial Loans | Financial Asset, Not Past Due | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total loans	50,226	52,396
Commercial Loans | Financial Asset, Not Past Due | Commercial mortgage
Financing Receivable, Past Due [Line Items]
Total loans	14,174	12,548
Commercial Loans | Financial Asset, Not Past Due | Commercial Real Estate : Construction
Financing Receivable, Past Due [Line Items]
Total loans	1,978	1,986
Commercial Loans | Financial Asset, Not Past Due | Commercial real estate loans
Financing Receivable, Past Due [Line Items]
Total loans	16,152	14,534
Commercial Loans | Financial Asset, Not Past Due | Commercial lease financing
Financing Receivable, Past Due [Line Items]
Total loans	4,061	4,369
Commercial Loans | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Total loans	397	681
Commercial Loans | Financial Asset, Past Due | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Total loans	299	511
Commercial Loans | Financial Asset, Past Due | Commercial mortgage
Financing Receivable, Past Due [Line Items]
Total loans	70	139
Commercial Loans | Financial Asset, Past Due | Commercial Real Estate : Construction
Financing Receivable, Past Due [Line Items]
Total loans	18	1
Commercial Loans | Financial Asset, Past Due | Commercial real estate loans
Financing Receivable, Past Due [Line Items]
Total loans	88	140
Commercial Loans | Financial Asset, Past Due | Commercial lease financing
Financing Receivable, Past Due [Line Items]
Total loans	10	30
Consumer Loans
Financing Receivable, Past Due [Line Items]
Total loans	31,018	29,205
Accrued interest	85
Consumer Loans | Nonperforming
Financing Receivable, Past Due [Line Items]
Total loans	215	288
Consumer Loans | Real estate — residential mortgage
Financing Receivable, Past Due [Line Items]
Total loans	15,756	9,298
Consumer Loans | Real estate — residential mortgage | Nonperforming
Financing Receivable, Past Due [Line Items]
Total loans	72	110
Consumer Loans | Home equity loans
Financing Receivable, Past Due [Line Items]
Total loans	8,467	9,360
Consumer Loans | Home equity loans | Nonperforming
Financing Receivable, Past Due [Line Items]
Total loans	135	154
Consumer Loans | Consumer direct loans
Financing Receivable, Past Due [Line Items]
Total loans	5,753	4,714
Consumer Loans | Consumer direct loans | Nonperforming
Financing Receivable, Past Due [Line Items]
Total loans	4	5
Consumer Loans | Commercial credit card
Financing Receivable, Past Due [Line Items]
Total loans	972	989
Consumer Loans | Commercial credit card | Nonperforming
Financing Receivable, Past Due [Line Items]
Total loans	3	2
Consumer Loans | Consumer indirect loans
Financing Receivable, Past Due [Line Items]
Total loans	70	4,844
Consumer Loans | Consumer indirect loans | Nonperforming
Financing Receivable, Past Due [Line Items]
Total loans	1	17
Consumer Loans | Financial Asset, 30 to 59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	41	82
Consumer Loans | Financial Asset, 30 to 59 Days Past Due | Real estate — residential mortgage
Financing Receivable, Past Due [Line Items]
Total loans	7	11
Consumer Loans | Financial Asset, 30 to 59 Days Past Due | Home equity loans
Financing Receivable, Past Due [Line Items]
Total loans	21	34
Consumer Loans | Financial Asset, 30 to 59 Days Past Due | Consumer direct loans
Financing Receivable, Past Due [Line Items]
Total loans	8	7
Consumer Loans | Financial Asset, 30 to 59 Days Past Due | Commercial credit card
Financing Receivable, Past Due [Line Items]
Total loans	4	5
Consumer Loans | Financial Asset, 30 to 59 Days Past Due | Consumer indirect loans
Financing Receivable, Past Due [Line Items]
Total loans	1	25
Consumer Loans | Financial Asset, 60 to 89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	14	37
Consumer Loans | Financial Asset, 60 to 89 Days Past Due | Real estate — residential mortgage
Financing Receivable, Past Due [Line Items]
Total loans	3	3
Consumer Loans | Financial Asset, 60 to 89 Days Past Due | Home equity loans
Financing Receivable, Past Due [Line Items]
Total loans	6	20
Consumer Loans | Financial Asset, 60 to 89 Days Past Due | Consumer direct loans
Financing Receivable, Past Due [Line Items]
Total loans	2	4
Consumer Loans | Financial Asset, 60 to 89 Days Past Due | Commercial credit card
Financing Receivable, Past Due [Line Items]
Total loans	3	3
Consumer Loans | Financial Asset, 60 to 89 Days Past Due | Consumer indirect loans
Financing Receivable, Past Due [Line Items]
Total loans	0	7
Consumer Loans | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans	20	24
Consumer Loans | Financial Asset, Equal to or Greater than 90 Days Past Due | Real estate — residential mortgage
Financing Receivable, Past Due [Line Items]
Total loans	5	1
Consumer Loans | Financial Asset, Equal to or Greater than 90 Days Past Due | Home equity loans
Financing Receivable, Past Due [Line Items]
Total loans	6	9
Consumer Loans | Financial Asset, Equal to or Greater than 90 Days Past Due | Consumer direct loans
Financing Receivable, Past Due [Line Items]
Total loans	3	4
Consumer Loans | Financial Asset, Equal to or Greater than 90 Days Past Due | Commercial credit card
Financing Receivable, Past Due [Line Items]
Total loans	6	7
Consumer Loans | Financial Asset, Equal to or Greater than 90 Days Past Due | Consumer indirect loans
Financing Receivable, Past Due [Line Items]
Total loans	0	3
Consumer Loans | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Total loans	30,728	28,774
Consumer Loans | Financial Asset, Not Past Due | Real estate — residential mortgage
Financing Receivable, Past Due [Line Items]
Total loans	15,669	9,173
Consumer Loans | Financial Asset, Not Past Due | Home equity loans
Financing Receivable, Past Due [Line Items]
Total loans	8,299	9,143
Consumer Loans | Financial Asset, Not Past Due | Consumer direct loans
Financing Receivable, Past Due [Line Items]
Total loans	5,736	4,694
Consumer Loans | Financial Asset, Not Past Due | Commercial credit card
Financing Receivable, Past Due [Line Items]
Total loans	956	972
Consumer Loans | Financial Asset, Not Past Due | Consumer indirect loans
Financing Receivable, Past Due [Line Items]
Total loans	68	4,792
Consumer Loans | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Total loans	290	431
Consumer Loans | Financial Asset, Past Due | Real estate — residential mortgage
Financing Receivable, Past Due [Line Items]
Total loans	87	125
Consumer Loans | Financial Asset, Past Due | Home equity loans
Financing Receivable, Past Due [Line Items]
Total loans	168	217
Consumer Loans | Financial Asset, Past Due | Consumer direct loans
Financing Receivable, Past Due [Line Items]
Total loans	17	20
Consumer Loans | Financial Asset, Past Due | Commercial credit card
Financing Receivable, Past Due [Line Items]
Total loans	16	17
Consumer Loans | Financial Asset, Past Due | Consumer indirect loans
Financing Receivable, Past Due [Line Items]
Total loans	$ 2	$ 52