Loans and ACL - Delinquency Status of Loans that Were Modified During the Period (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	$ 855	$ 2,200
Financial Asset, Not Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	766
Financing Receivables 30 To 89 Days Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	36
Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	53
Nonperforming
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	180	$ 214
Nonperforming | Financial Asset, Not Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	131
Nonperforming | Financing Receivables 30 To 89 Days Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	10
Nonperforming | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	39
Commercial: | Commercial and industrial
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	441
Commercial: | Commercial and industrial | Financial Asset, Not Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	406
Commercial: | Commercial and industrial | Financing Receivables 30 To 89 Days Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	1
Commercial: | Commercial and industrial | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	34
Commercial: | CRE
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	174
Commercial: | CRE | Financial Asset, Not Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	174
Commercial: | CRE | Financing Receivables 30 To 89 Days Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	0
Commercial: | CRE | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	0
Commercial: | Commercial construction
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	1
Commercial: | Commercial construction | Financial Asset, Not Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	1
Commercial: | Commercial construction | Financing Receivables 30 To 89 Days Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	0
Commercial: | Commercial construction | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	0
Consumer: | Residential mortgage
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	203
Consumer: | Residential mortgage | Financial Asset, Not Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	153
Consumer: | Residential mortgage | Financing Receivables 30 To 89 Days Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	33
Consumer: | Residential mortgage | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	17
Consumer: | Home equity
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	3
Consumer: | Home equity | Financial Asset, Not Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	3
Consumer: | Home equity | Financing Receivables 30 To 89 Days Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	0
Consumer: | Home equity | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	0
Consumer: | Indirect auto
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	21
Consumer: | Indirect auto | Financial Asset, Not Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	19
Consumer: | Indirect auto | Financing Receivables 30 To 89 Days Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	1
Consumer: | Indirect auto | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	1
Consumer: | Other consumer
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	7
Consumer: | Other consumer | Financial Asset, Not Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	7
Consumer: | Other consumer | Financing Receivables 30 To 89 Days Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	0
Consumer: | Other consumer | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	0
Credit card
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	5
Credit card | Financial Asset, Not Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	3
Credit card | Financing Receivables 30 To 89 Days Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	1
Credit card | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Modified, Past Due [Line Items]
Financing Receivable, Modified, Accumulated	$ 1