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, 2023	Sep. 30, 2023
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 171	$ 484
Commercial
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 124	$ 355
% of Total Class	0.17%	0.47%
Commercial | Term Extension
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 115	$ 337
Commercial | Term Extension and Interest Rate Reduction
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	1	4
Commercial | Interest Rate Reduction
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount		1
Commercial | Term Extension and Payment Deferral
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	8	8
Commercial | Payment Deferral
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount		5
Commercial | Commercial and industrial loans
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 101	$ 191
% of Total Class	0.18%	0.34%
Commercial | Commercial and industrial loans | Term Extension
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 92	$ 176
Commercial | Commercial and industrial loans | Term Extension and Interest Rate Reduction
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	1	1
Commercial | Commercial and industrial loans | Interest Rate Reduction
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount		1
Commercial | Commercial and industrial loans | Term Extension and Payment Deferral
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	8	8
Commercial | Commercial and industrial loans | Payment Deferral
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount		5
Commercial | Commercial mortgage owner-occupied loans
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 3	$ 24
% of Total Class	0.06%	0.45%
Commercial | Commercial mortgage owner-occupied loans | Term Extension
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 3	$ 24
Commercial | Commercial mortgage owner-occupied loans | Term Extension and Interest Rate Reduction
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0
Commercial | Commercial mortgage owner-occupied loans | Interest Rate Reduction
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount		0
Commercial | Commercial mortgage owner-occupied loans | Term Extension and Payment Deferral
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0
Commercial | Commercial mortgage owner-occupied loans | Payment Deferral
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount		0
Commercial | Commercial mortgage nonowner-occupied loans
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 1	$ 24
% of Total Class	0.02%	0.42%
Commercial | Commercial mortgage nonowner-occupied loans | Term Extension
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 1	$ 21
Commercial | Commercial mortgage nonowner-occupied loans | Term Extension and Interest Rate Reduction
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	3
Commercial | Commercial mortgage nonowner-occupied loans | Interest Rate Reduction
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount		0
Commercial | Commercial mortgage nonowner-occupied loans | Term Extension and Payment Deferral
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0
Commercial | Commercial mortgage nonowner-occupied loans | Payment Deferral
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount		0
Commercial | Commercial construction loans
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 19	$ 116
% of Total Class	0.34%	2.08%
Commercial | Commercial construction loans | Term Extension
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 19	$ 116
Commercial | Commercial construction loans | Term Extension and Interest Rate Reduction
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0
Commercial | Commercial construction loans | Interest Rate Reduction
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount		0
Commercial | Commercial construction loans | Term Extension and Payment Deferral
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0
Commercial | Commercial construction loans | Payment Deferral
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount		0
Residential Mortgage
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 31	$ 89
% of Total Class	0.18%	0.51%
Residential Mortgage | Term Extension and Payment Deferral
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 27	$ 69
% of Total Class	0.15%	0.40%
Residential Mortgage | Payment Deferral
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 3	$ 16
% of Total Class	0.02%	0.09%
Residential Mortgage | Term Extension, Interest Rate Reduction and Payment Deferral
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 1	$ 4
% of Total Class	0.01%	0.02%
Consumer
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 16	$ 40
% of Total Class	0.06%	0.14%
Consumer | Interest Rate Reduction
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 11	$ 26
Consumer | Term Extension and Payment Deferral
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	1	2
Consumer | Payment Deferral
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	2	5
Consumer | Term Extension, Interest Rate Reduction and Payment Deferral
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	2	7
Consumer | Home equity
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 5	$ 12
% of Total Class	0.13%	0.31%
Consumer | Home equity | Interest Rate Reduction
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 2	$ 3
Consumer | Home equity | Term Extension and Payment Deferral
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	1	2
Consumer | Home equity | Payment Deferral
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0
Consumer | Home equity | Term Extension, Interest Rate Reduction and Payment Deferral
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	2	7
Consumer | Credit card
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 9	$ 23
% of Total Class	0.50%	1.27%
Consumer | Credit card | Interest Rate Reduction
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 9	$ 23
Consumer | Credit card | Term Extension and Payment Deferral
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0
Consumer | Credit card | Payment Deferral
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0
Consumer | Credit card | Term Extension, Interest Rate Reduction and Payment Deferral
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0
Consumer | Other consumer loans
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 2	$ 5
% of Total Class	0.03%	0.08%
Consumer | Other consumer loans | Interest Rate Reduction
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 0	$ 0
Consumer | Other consumer loans | Term Extension and Payment Deferral
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	0	0
Consumer | Other consumer loans | Payment Deferral
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	2	5
Consumer | Other consumer loans | Term Extension, Interest Rate Reduction and Payment Deferral
Financing Receivable, Modifications
Financing receivable, excluding accrued interest, modified in period, amount	$ 0	$ 0