Asset Quality - Breakdown of Nonperforming TDRs by Loans Category (Details) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2022 USD ($) loan	Dec. 31, 2021 USD ($) loan
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	4,275	4,429
Pre-modification Outstanding Recorded Investment	$ 340	$ 308
Post-modification Outstanding Recorded Investment	$ 254	$ 220
Prior-Year Accruing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	2,982	3,049
Pre-modification Outstanding Recorded Investment	$ 159	$ 160
Post-modification Outstanding Recorded Investment	$ 120	$ 121
Prior-Year Accruing | Total commercial loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	17	12
Pre-modification Outstanding Recorded Investment	$ 1	$ 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	2,965	3,037
Pre-modification Outstanding Recorded Investment	$ 158	$ 160
Post-modification Outstanding Recorded Investment	$ 120	$ 121
Non-performing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	1,293	1,380
Pre-modification Outstanding Recorded Investment	$ 181	$ 148
Post-modification Outstanding Recorded Investment	$ 134	$ 99
Non-performing Loans | Total commercial loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	41	39
Pre-modification Outstanding Recorded Investment	$ 114	$ 80
Post-modification Outstanding Recorded Investment	$ 75	$ 39
Non-performing Loans | Total consumer loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	1,252	1,341
Pre-modification Outstanding Recorded Investment	$ 67	$ 68
Post-modification Outstanding Recorded Investment	$ 59	$ 60
Total commercial real estate loans | Prior-Year Accruing | Commercial Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	0	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	4	3
Pre-modification Outstanding Recorded Investment	$ 50	$ 50
Post-modification Outstanding Recorded Investment	$ 23	$ 25
Commercial and Industrial | Prior-Year Accruing | Total commercial loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	17	11
Pre-modification Outstanding Recorded Investment	$ 1	$ 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	37	36
Pre-modification Outstanding Recorded Investment	$ 64	$ 30
Post-modification Outstanding Recorded Investment	$ 52	$ 14
Commercial mortgage | Prior-Year Accruing | Commercial Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	0	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	4	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	443	455
Pre-modification Outstanding Recorded Investment	$ 41	$ 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	234	220
Pre-modification Outstanding Recorded Investment	$ 29	$ 26
Post-modification Outstanding Recorded Investment	$ 26	$ 24
Home equity loans | Prior-Year Accruing | Total consumer loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	1,563	1,628
Pre-modification Outstanding Recorded Investment	$ 97	$ 97
Post-modification Outstanding Recorded Investment	$ 74	$ 75
Home equity loans | Non-performing Loans | Total consumer loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	478	531
Pre-modification Outstanding Recorded Investment	$ 32	$ 36
Post-modification Outstanding Recorded Investment	$ 28	$ 31
Consumer direct loans | Prior-Year Accruing | Total consumer loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	257	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	180	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	595	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	343	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	107	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	17	23
Pre-modification Outstanding Recorded Investment	$ 2	$ 1
Post-modification Outstanding Recorded Investment	$ 1	$ 1