Loans and ACL - Delinquency Status of Loans that Were Modified During the Period (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	$ 3,692	$ 3,257
Financial Asset, Not Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	3,160	2,731
Financing Receivables 30 To 89 Days Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	340	365
Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	192	161
Nonperforming
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	305	401
Nonperforming | Financial Asset, Not Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	166	232
Nonperforming | Financing Receivables 30 To 89 Days Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	35	78
Nonperforming | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	104	91
Commercial: | Commercial and industrial
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	948	1,036
Commercial: | Commercial and industrial | Financial Asset, Not Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	922	974
Commercial: | Commercial and industrial | Financing Receivables 30 To 89 Days Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	3	44
Commercial: | Commercial and industrial | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	23	18
Commercial: | CRE
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	679	323
Commercial: | CRE | Financial Asset, Not Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	678	313
Commercial: | CRE | Financing Receivables 30 To 89 Days Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	0	7
Commercial: | CRE | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	1	3
Commercial: | Commercial construction
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	143	79
Commercial: | Commercial construction | Financial Asset, Not Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	143	79
Commercial: | Commercial construction | Financing Receivables 30 To 89 Days Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	0	0
Commercial: | Commercial construction | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	0	0
Consumer: | Residential mortgage
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	586	476
Consumer: | Residential mortgage | Financial Asset, Not Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	343	279
Consumer: | Residential mortgage | Financing Receivables 30 To 89 Days Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	111	95
Consumer: | Residential mortgage | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	132	102
Consumer: | Home equity
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	4	9
Consumer: | Home equity | Financial Asset, Not Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	4	9
Consumer: | Home equity | Financing Receivables 30 To 89 Days Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	0	0
Consumer: | Home equity | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	0	0
Consumer: | Indirect auto
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	1,273	1,273
Consumer: | Indirect auto | Financial Asset, Not Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	1,021	1,025
Consumer: | Indirect auto | Financing Receivables 30 To 89 Days Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	220	213
Consumer: | Indirect auto | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	32	35
Consumer: | Other consumer
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	34	36
Consumer: | Other consumer | Financial Asset, Not Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	31	32
Consumer: | Other consumer | Financing Receivables 30 To 89 Days Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	2	3
Consumer: | Other consumer | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	1	1
Credit card
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	25	25
Credit card | Financial Asset, Not Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	18	20
Credit card | Financing Receivables 30 To 89 Days Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	4	3
Credit card | Financial Asset, Equal to or Greater than 90 Days Past Due
Financing Receivable, Modified
Financing Receivable, Modified, Accumulated	$ 3	$ 2