Loans and ACL - Nonperforming Loans (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Financing Receivable, Nonperforming [Line Items]
Financing Receivable, Excluding Accrued Interest, Nonaccrual, No Allowance	$ 127	$ 109
Financing Receivable, Excluding Accrued Interest, Nonaccrual, With Related Allowance	1,361	1,320
Commercial: \| Commercial and industrial
Financing Receivable, Nonperforming [Line Items]
Financing Receivable, Excluding Accrued Interest, Nonaccrual, No Allowance	101	52
Financing Receivable, Excluding Accrued Interest, Nonaccrual, With Related Allowance	485	469
Commercial: \| CRE
Financing Receivable, Nonperforming [Line Items]
Financing Receivable, Excluding Accrued Interest, Nonaccrual, No Allowance	23	32
Financing Receivable, Excluding Accrued Interest, Nonaccrual, With Related Allowance	271	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	2	3
Consumer: \| Residential mortgage
Financing Receivable, Nonperforming [Line Items]
Financing Receivable, Excluding Accrued Interest, Nonaccrual, No Allowance	2	1
Financing Receivable, Excluding Accrued Interest, Nonaccrual, With Related Allowance	177	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	113	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	248	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	$ 65	$ 66