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, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 184	$ 171	$ 373	$ 484
% of Total Class	0.16%	0.14%	0.32%	0.40%
Commercial
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 150	$ 124	$ 268	$ 355
% of Total Class	0.22%	0.17%	0.39%	0.47%
Commercial | Term Extension
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 129	$ 115	$ 223	$ 337
Commercial | Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	19	0	24	5
Commercial | Term Extension and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	2	8	20	8
Commercial | Other
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	1	1	5
Commercial | Commercial and industrial loans
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 105	$ 101	$ 208	$ 191
% of Total Class	0.21%	0.18%	0.41%	0.34%
Commercial | Commercial and industrial loans | Term Extension
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 84	$ 92	$ 164	$ 176
Commercial | Commercial and industrial loans | Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	19	0	23	5
Commercial | Commercial and industrial loans | Term Extension and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	2	8	20	8
Commercial | Commercial and industrial loans | Other
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	1	1	2
Commercial | Commercial mortgage owner-occupied loans
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 11	$ 3	$ 26	$ 24
% of Total Class	0.20%	0.06%	0.48%	0.45%
Commercial | Commercial mortgage owner-occupied loans | Term Extension
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 11	$ 3	$ 25	$ 24
Commercial | Commercial mortgage owner-occupied loans | Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0	1	0
Commercial | Commercial mortgage owner-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 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	$ 28	$ 1	$ 28	$ 24
% of Total Class	0.47%	0.02%	0.47%	0.42%
Commercial | Commercial mortgage nonowner-occupied loans | Term Extension
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 28	$ 1	$ 28	$ 21
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 | 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 | Other
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0	0	3
Commercial | Commercial construction loans
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 6	$ 19	$ 6	$ 116
% of Total Class	0.10%	0.34%	0.10%	2.08%
Commercial | Commercial construction loans | Term Extension
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 6	$ 19	$ 6	$ 116
Commercial | Commercial construction loans | Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0	0	0
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 | 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	$ 22	$ 31	$ 74	$ 89
% of Total Class	0.13%	0.18%	0.43%	0.51%
Residential Mortgage | Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 1	$ 3	$ 5	$ 16
% of Total Class	0.01%	0.02%	0.03%	0.09%
Residential Mortgage | Term Extension and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 17	$ 27	$ 61	$ 69
% of Total Class	0.10%	0.15%	0.36%	0.40%
Residential Mortgage | Term Extension, Interest Rate Reduction and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 4	$ 1	$ 8	$ 4
% of Total Class	0.02%	0.01%	0.05%	0.02%
Consumer
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 12	$ 16	$ 31	$ 40
% of Total Class	0.04%	0.06%	0.11%	0.14%
Consumer | Interest Rate Reduction
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 8	$ 11	$ 20	$ 26
Consumer | Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	1	2	3	5
Consumer | Term Extension and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	1	1	2
Consumer | Term Extension, Interest Rate Reduction and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	3	2	7	7
Consumer | Home equity
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 4	$ 5	$ 11	$ 12
% of Total Class	0.10%	0.13%	0.27%	0.31%
Consumer | Home equity | Interest Rate Reduction
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 1	$ 2	$ 3	$ 3
Consumer | Home equity | Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0	0	0
Consumer | Home equity | Term Extension and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	1	1	2
Consumer | Home equity | Term Extension, Interest Rate Reduction and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	3	2	7	7
Consumer | Credit card
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 7	$ 9	$ 17	$ 23
% of Total Class	0.41%	0.50%	1.00%	1.27%
Consumer | Credit card | Interest Rate Reduction
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 7	$ 9	$ 17	$ 23
Consumer | Credit card | Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0	0	0
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 | 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	$ 2	$ 3	$ 4
% of Total Class	0.04%	0.06%	0.12%	0.13%
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 | Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	1	2	3	4
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 | 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	$ 0	$ 1
% of Total Class	0.00%	0.00%	0.00%	0.03%
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 | Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0	0	1
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 | Term Extension, Interest Rate Reduction and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 0	$ 0	$ 0	$ 0