Credit Quality and the Allowance for Loan and Lease Losses - Summary of Amortized Cost Basis of Loans Modified for Borrowers Experiencing Financial Difficulty (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 349	$ 184	$ 609	$ 373
% of Total Class	0.28%	0.16%	0.49%	0.32%
Commercial
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 308	$ 150	$ 507	$ 268
% of Total Class	0.43%	0.22%	0.71%	0.39%
Commercial | Term Extension
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 266	$ 129	$ 404	$ 223
Commercial | Term Extension and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	11	2	14	20
Commercial | Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	28	19	85	24
Commercial | Other
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	3	0	4	1
Commercial | Commercial and industrial loans
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 137	$ 105	$ 237	$ 208
% of Total Class	0.25%	0.21%	0.44%	0.41%
Commercial | Commercial and industrial loans | Term Extension
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 137	$ 84	$ 193	$ 164
Commercial | Commercial and industrial loans | Term Extension and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	2	3	20
Commercial | Commercial and industrial loans | Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	19	40	23
Commercial | Commercial and industrial loans | Other
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0	1	1
Commercial | Commercial mortgage owner-occupied loans
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 75	$ 11	$ 112	$ 26
% of Total Class	1.24%	0.20%	1.85%	0.48%
Commercial | Commercial mortgage owner-occupied loans | Term Extension
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 64	$ 11	$ 100	$ 25
Commercial | Commercial mortgage owner-occupied loans | Term Extension and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	11	0	11	0
Commercial | Commercial mortgage owner-occupied loans | Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0	1	1
Commercial | Commercial mortgage owner-occupied loans | Other
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0	0	0
Commercial | Commercial mortgage nonowner-occupied loans
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 68	$ 28	$ 68	$ 28
% of Total Class	1.15%	0.47%	1.15%	0.47%
Commercial | Commercial mortgage nonowner-occupied loans | Term Extension
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 65	$ 28	$ 65	$ 28
Commercial | Commercial mortgage nonowner-occupied loans | Term Extension and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0	0	0
Commercial | Commercial mortgage nonowner-occupied loans | Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0	0	0
Commercial | Commercial mortgage nonowner-occupied loans | Other
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	3	0	3	0
Commercial | Commercial construction loans
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 28	$ 6	$ 90	$ 6
% of Total Class	0.53%	0.10%	1.69%	0.10%
Commercial | Commercial construction loans | Term Extension
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 0	$ 6	$ 46	$ 6
Commercial | Commercial construction loans | Term Extension and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0	0	0
Commercial | Commercial construction loans | Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	28	0	44	0
Commercial | Commercial construction loans | Other
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0	0	0
Residential Mortgage
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 29	$ 22	$ 72	$ 74
% of Total Class	0.16%	0.13%	0.41%	0.43%
Residential Mortgage | Term Extension and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 21	$ 17	$ 57	$ 61
% of Total Class	0.12%	0.10%	0.32%	0.36%
Residential Mortgage | Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 0	$ 1	$ 1	$ 5
% of Total Class	0.00%	0.01%	0.01%	0.03%
Residential Mortgage | Term Extension, Interest Rate Reduction and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 8	$ 4	$ 14	$ 8
% of Total Class	0.05%	0.02%	0.08%	0.05%
Consumer
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 12	$ 12	$ 30	$ 31
% of Total Class	0.04%	0.04%	0.10%	0.11%
Consumer | Term Extension and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 0	$ 0	$ 1	$ 1
Consumer | Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	1	1	5	3
Consumer | Interest Rate Reduction
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	6	8	15	20
Consumer | Term Extension, Interest Rate Reduction and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	4	3	9	7
Consumer | Home equity
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 5	$ 4	$ 11	$ 11
% of Total Class	0.11%	0.10%	0.24%	0.27%
Consumer | Home equity | Term Extension and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 1	$ 0	$ 1	$ 1
Consumer | Home equity | Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0	0	0
Consumer | Home equity | Interest Rate Reduction
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	1	1	3
Consumer | Home equity | Term Extension, Interest Rate Reduction and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	4	3	9	7
Consumer | Credit card
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 6	$ 7	$ 14	$ 17
% of Total Class	0.35%	0.41%	0.83%	1.00%
Consumer | Credit card | Term Extension and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 0	$ 0	$ 0	$ 0
Consumer | Credit card | Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0	0	0
Consumer | Credit card | Interest Rate Reduction
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	6	7	14	17
Consumer | Credit card | Term Extension, Interest Rate Reduction and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0	0	0
Consumer | Other consumer loans
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 1	$ 1	$ 3	$ 3
% of Total Class	0.04%	0.04%	0.13%	0.12%
Consumer | Other consumer loans | Term Extension and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 0	$ 0	$ 0	$ 0
Consumer | Other consumer loans | Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	1	1	3	3
Consumer | Other consumer loans | Interest Rate Reduction
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0	0	0
Consumer | Other consumer loans | Term Extension, Interest Rate Reduction and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0	0	0
Consumer | Solar energy installation loans
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 0	$ 0	$ 2	$ 0
% of Total Class	0.00%	0.00%	0.05%	0.00%
Consumer | Solar energy installation loans | Term Extension and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 0	$ 0	$ 0	$ 0
Consumer | Solar energy installation loans | Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0	2	0
Consumer | Solar energy installation loans | Interest Rate Reduction
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0	0	0
Consumer | Solar energy installation loans | Term Extension, Interest Rate Reduction and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 0	$ 0	$ 0	$ 0