Asset Quality - Breakdown of Nonperforming TDRs by Loans Category (Details) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2022 USD ($) loan	Dec. 31, 2021 USD ($) loan
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	4,344	4,429
Pre-modification Outstanding Recorded Investment	$ 301	$ 308
Post-modification Outstanding Recorded Investment	$ 216	$ 220
Prior-Year Accruing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	3,054	3,049
Pre-modification Outstanding Recorded Investment	$ 161	$ 160
Post-modification Outstanding Recorded Investment	$ 122	$ 121
Prior-Year Accruing | Total commercial loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	12	12
Pre-modification Outstanding Recorded Investment	$ 0	$ 0
Post-modification Outstanding Recorded Investment	$ 0	$ 0
Prior-Year Accruing | Total consumer loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	3,042	3,037
Pre-modification Outstanding Recorded Investment	$ 161	$ 160
Post-modification Outstanding Recorded Investment	$ 122	$ 121
Non-performing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	1,290	1,380
Pre-modification Outstanding Recorded Investment	$ 140	$ 148
Post-modification Outstanding Recorded Investment	$ 94	$ 99
Non-performing Loans | Total commercial loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	43	39
Pre-modification Outstanding Recorded Investment	$ 75	$ 80
Post-modification Outstanding Recorded Investment	$ 35	$ 39
Non-performing Loans | Total consumer loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	1,247	1,341
Pre-modification Outstanding Recorded Investment	$ 65	$ 68
Post-modification Outstanding Recorded Investment	$ 59	$ 60
Commercial and Industrial | Prior-Year Accruing | Total commercial loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	11	11
Pre-modification Outstanding Recorded Investment	$ 0	$ 0
Post-modification Outstanding Recorded Investment	$ 0	$ 0
Commercial and Industrial | Non-performing Loans | Total commercial loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	40	36
Pre-modification Outstanding Recorded Investment	$ 25	$ 30
Post-modification Outstanding Recorded Investment	$ 12	$ 14
Commercial mortgage | Prior-Year Accruing | Commercial Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	1	1
Pre-modification Outstanding Recorded Investment	$ 0	$ 0
Post-modification Outstanding Recorded Investment	$ 0	$ 0
Commercial mortgage | Non-performing Loans | Commercial Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	3	3
Pre-modification Outstanding Recorded Investment	$ 50	$ 50
Post-modification Outstanding Recorded Investment	$ 23	$ 25
Total commercial real estate loans | Prior-Year Accruing | Commercial Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	1	1
Pre-modification Outstanding Recorded Investment	$ 0	$ 0
Post-modification Outstanding Recorded Investment	$ 0	$ 0
Total commercial real estate loans | Non-performing Loans | Commercial Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	3	3
Pre-modification Outstanding Recorded Investment	$ 50	$ 50
Post-modification Outstanding Recorded Investment	$ 23	$ 25
Real estate — residential mortgage | Prior-Year Accruing | Total consumer loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	457	455
Pre-modification Outstanding Recorded Investment	$ 42	$ 39
Post-modification Outstanding Recorded Investment	$ 35	$ 33
Real estate — residential mortgage | Non-performing Loans | Total consumer loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	224	220
Pre-modification Outstanding Recorded Investment	$ 27	$ 26
Post-modification Outstanding Recorded Investment	$ 25	$ 24
Home equity loans | Prior-Year Accruing | Total consumer loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	1,612	1,628
Pre-modification Outstanding Recorded Investment	$ 99	$ 97
Post-modification Outstanding Recorded Investment	$ 76	$ 75
Home equity loans | Non-performing Loans | Total consumer loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	486	531
Pre-modification Outstanding Recorded Investment	$ 32	$ 36
Post-modification Outstanding Recorded Investment	$ 29	$ 31
Consumer direct loans | Prior-Year Accruing | Total consumer loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	253	236
Pre-modification Outstanding Recorded Investment	$ 4	$ 5
Post-modification Outstanding Recorded Investment	$ 3	$ 3
Consumer direct loans | Non-performing Loans | Total consumer loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	172	207
Pre-modification Outstanding Recorded Investment	$ 2	$ 3
Post-modification Outstanding Recorded Investment	$ 2	$ 2
Credit cards | Prior-Year Accruing | Total consumer loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	607	579
Pre-modification Outstanding Recorded Investment	$ 4	$ 4
Post-modification Outstanding Recorded Investment	$ 2	$ 2
Credit cards | Non-performing Loans | Total consumer loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	345	360
Pre-modification Outstanding Recorded Investment	$ 2	$ 2
Post-modification Outstanding Recorded Investment	$ 2	$ 2
Consumer indirect loans | Prior-Year Accruing | Total consumer loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	113	139
Pre-modification Outstanding Recorded Investment	$ 12	$ 15
Post-modification Outstanding Recorded Investment	$ 6	$ 8
Consumer indirect loans | Non-performing Loans | Total consumer loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	20	23
Pre-modification Outstanding Recorded Investment	$ 2	$ 1
Post-modification Outstanding Recorded Investment	$ 1	$ 1