Credit Quality and the Allowance for Loan and Lease Losses - Summary of Amortized Cost Basis of Commercial Loans Modified for Borrowers Experiencing Financial Difficulty (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2026	Mar. 31, 2025
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 362	$ 254
Loan modification program, percentage of modifications to total portfolio	0.21%	0.21%
Commercial
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 334	$ 224
Loan modification program, percentage of modifications to total portfolio	0.28%	0.31%
Commercial \| Term Extension
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 302	$ 87
Commercial \| Term Extension and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	13	30
Commercial \| Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	107
Commercial \| Other
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	19	0
Commercial \| Commercial and industrial loans
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 289	$ 121
Loan modification program, percentage of modifications to total portfolio	0.34%	0.23%
Commercial \| Commercial and industrial loans \| Term Extension
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 258	$ 50
Commercial \| Commercial and industrial loans \| Term Extension and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	12	6
Commercial \| Commercial and industrial loans \| Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	65
Commercial \| Commercial and industrial loans \| Other
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	19	0
Commercial \| Commercial mortgage owner-occupied loans
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 9	$ 29
Loan modification program, percentage of modifications to total portfolio	0.07%	0.47%
Commercial \| Commercial mortgage owner-occupied loans \| Term Extension
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 9	$ 5
Commercial \| Commercial mortgage owner-occupied loans \| Term Extension and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	24
Commercial \| Commercial mortgage owner-occupied loans \| Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0
Commercial \| Commercial mortgage owner-occupied loans \| Other
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0
Commercial \| Commercial mortgage nonowner-occupied loans
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 4	$ 24
Loan modification program, percentage of modifications to total portfolio	0.03%	0.39%
Commercial \| Commercial mortgage nonowner-occupied loans \| Term Extension
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 3	$ 24
Commercial \| Commercial mortgage nonowner-occupied loans \| Term Extension and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	1	0
Commercial \| Commercial mortgage nonowner-occupied loans \| Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0
Commercial \| Commercial mortgage nonowner-occupied loans \| Other
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0
Commercial \| Commercial construction loans
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 32	$ 50
Loan modification program, percentage of modifications to total portfolio	0.38%	0.84%
Commercial \| Commercial construction loans \| Term Extension
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 32	$ 8
Commercial \| Commercial construction loans \| Term Extension and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0
Commercial \| Commercial construction loans \| Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	42
Commercial \| Commercial construction loans \| Other
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 0	$ 0

Credit Quality and the Allowance for Loan and Lease Losses - Summary of Amortized Cost Basis of Commercial Loans Modified for Borrowers Experiencing Financial Difficulty (Details) - USD ($)
$ in Millions