Loans and ACL - Nonperforming Loans (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Financing Receivable, Nonperforming [Line Items]
Financing Receivable, Excluding Accrued Interest, Nonaccrual, No Allowance	$ 88	$ 109
Financing Receivable, Excluding Accrued Interest, Nonaccrual, With Related Allowance	1,163	1,320
Commercial: | Commercial and industrial
Financing Receivable, Nonperforming [Line Items]
Financing Receivable, Excluding Accrued Interest, Nonaccrual, No Allowance	76	52
Financing Receivable, Excluding Accrued Interest, Nonaccrual, With Related Allowance	444	469
Commercial: | CRE
Financing Receivable, Nonperforming [Line Items]
Financing Receivable, Excluding Accrued Interest, Nonaccrual, No Allowance	7	32
Financing Receivable, Excluding Accrued Interest, Nonaccrual, With Related Allowance	121	266
Commercial: | Commercial construction
Financing Receivable, Nonperforming [Line Items]
Financing Receivable, Excluding Accrued Interest, Nonaccrual, No Allowance	0	0
Financing Receivable, Excluding Accrued Interest, Nonaccrual, With Related Allowance	1	3
Consumer: | Residential mortgage
Financing Receivable, Nonperforming [Line Items]
Financing Receivable, Excluding Accrued Interest, Nonaccrual, No Allowance	4	1
Financing Receivable, Excluding Accrued Interest, Nonaccrual, With Related Allowance	187	165
Consumer: | Home equity
Financing Receivable, Nonperforming [Line Items]
Financing Receivable, Excluding Accrued Interest, Nonaccrual, No Allowance	1	1
Financing Receivable, Excluding Accrued Interest, Nonaccrual, With Related Allowance	106	115
Consumer: | Indirect auto
Financing Receivable, Nonperforming [Line Items]
Financing Receivable, Excluding Accrued Interest, Nonaccrual, No Allowance	0	23
Financing Receivable, Excluding Accrued Interest, Nonaccrual, With Related Allowance	240	236
Consumer: | Other consumer
Financing Receivable, Nonperforming [Line Items]
Financing Receivable, Excluding Accrued Interest, Nonaccrual, No Allowance	0	0
Financing Receivable, Excluding Accrued Interest, Nonaccrual, With Related Allowance	$ 64	$ 66