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		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 183	$ 331	$ 300	$ 444
% of Total Class	0.16%	0.27%	0.26%	0.36%
Commercial
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 144	$ 282	$ 226	$ 358
% of Total Class	0.20%	0.37%	0.31%	0.47%
Commercial | Term Extension
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 122	$ 275	$ 191	$ 348
Commercial | Term Extension and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	18	0	18	0
Commercial | Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	4	7	17	7
Commercial | Other
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0	0	3
Commercial | Commercial and industrial loans
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 116	$ 170	$ 183	$ 191
% of Total Class	0.22%	0.30%	0.35%	0.34%
Commercial | Commercial and industrial loans | Term Extension
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 95	$ 163	$ 149	$ 183
Commercial | Commercial and industrial loans | Term Extension and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	18	0	18	0
Commercial | Commercial and industrial loans | Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	3	7	16	7
Commercial | Commercial and industrial loans | Other
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0	0	1
Commercial | Commercial mortgage owner-occupied loans
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 24	$ 40	$ 34	$ 40
% of Total Class	0.44%	0.74%	0.63%	0.74%
Commercial | Commercial mortgage owner-occupied loans | Term Extension
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 23	$ 40	$ 33	$ 40
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 | Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	1	0	1	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	$ 0	$ 2	$ 5	$ 26
% of Total Class	0.00%	0.03%	0.08%	0.44%
Commercial | Commercial mortgage nonowner-occupied loans | Term Extension
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 0	$ 2	$ 5	$ 24
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	0	0	0	2
Commercial | Commercial construction loans
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 4	$ 70	$ 4	$ 101
% of Total Class	0.07%	1.28%	0.07%	1.84%
Commercial | Commercial construction loans | Term Extension
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 4	$ 70	$ 4	$ 101
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	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	$ 29	$ 36	$ 53	$ 59
% of Total Class	0.17%	0.21%	0.31%	0.34%
Residential Mortgage | Term Extension and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 24	$ 29	$ 45	$ 42
% of Total Class	0.14%	0.17%	0.26%	0.24%
Residential Mortgage | Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 3	$ 6	$ 5	$ 14
% of Total Class	0.02%	0.03%	0.03%	0.08%
Residential Mortgage | Term Extension, Interest Rate Reduction and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 2	$ 1	$ 3	$ 3
% of Total Class	0.01%	0.01%	0.02%	0.02%
Consumer
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 10	$ 13	$ 21	$ 27
% of Total Class	0.04%	0.05%	0.08%	0.10%
Consumer | Term Extension and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 0	$ 1	$ 1	$ 2
Consumer | Interest Rate Reduction
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	7	8	13	18
Consumer | Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	1	2	2	3
Consumer | Term Extension, Interest Rate Reduction and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	2	2	5	4
Consumer | Home equity
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 3	$ 3	$ 7	$ 7
% of Total Class	0.08%	0.08%	0.18%	0.18%
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 | Interest Rate Reduction
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 | Term Extension, Interest Rate Reduction and Payment Delay
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	2	2	5	4
Consumer | Credit card
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 6	$ 8	$ 12	$ 17
% of Total Class	0.35%	0.44%	0.69%	0.94%
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 | Interest Rate Reduction
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	6	8	12	17
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, 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	$ 2	$ 2
% of Total Class	0.04%	0.03%	0.08%	0.06%
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 | 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	1	2	2
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	$ 1	$ 0	$ 1
% of Total Class	0.00%	0.03%	0.00%	0.03%
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 | 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	1	0	1
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