Credit Quality and the Allowance for Loan and Lease Losses - Summary of Recorded Investment in Portfolio Loans and Leases by Age and Class (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	$ 116,485	$ 117,234
Commercial
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	71,916	72,746
90 Days Past Due and Still Accruing	11	8
Commercial | Current
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	71,645	72,547
Commercial | Total Past Due
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	271	199
Commercial | 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	143	93
Commercial | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	128	106
Commercial | Commercial and industrial loans
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	52,209	53,270
90 Days Past Due and Still Accruing	9	8
Commercial | Commercial and industrial loans | Current
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	52,009	53,107
Commercial | Commercial and industrial loans | Total Past Due
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	200	163
Commercial | Commercial and industrial loans | 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	76	61
Commercial | Commercial and industrial loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	124	102
Commercial | Commercial mortgage owner-occupied loans
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	5,357	5,200
90 Days Past Due and Still Accruing	0	0
Commercial | Commercial mortgage owner-occupied loans | Current
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	5,335	5,196
Commercial | Commercial mortgage owner-occupied loans | Total Past Due
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	22	4
Commercial | Commercial mortgage owner-occupied loans | 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	20	1
Commercial | Commercial mortgage owner-occupied loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	2	3
Commercial | Commercial mortgage nonowner-occupied loans
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	5,989	6,076
90 Days Past Due and Still Accruing	0	0
Commercial | Commercial mortgage nonowner-occupied loans | Current
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	5,985	6,061
Commercial | Commercial mortgage nonowner-occupied loans | Total Past Due
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	4	15
Commercial | Commercial mortgage nonowner-occupied loans | 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	4	14
Commercial | Commercial mortgage nonowner-occupied loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	0	1
Commercial | Commercial construction loans
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	5,789	5,621
90 Days Past Due and Still Accruing	0	0
Commercial | Commercial construction loans | Current
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	5,768	5,621
Commercial | Commercial construction loans | Total Past Due
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	21	0
Commercial | Commercial construction loans | 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	21	0
Commercial | Commercial construction loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	0	0
Commercial | Commercial leases
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	2,572	2,579
90 Days Past Due and Still Accruing	2	0
Commercial | Commercial leases | Current
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	2,548	2,562
Commercial | Commercial leases | Total Past Due
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	24	17
Commercial | Commercial leases | 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	22	17
Commercial | Commercial leases | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	$ 2	$ 0