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, 2026	Dec. 31, 2025
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	$ 176,250	$ 122,651
Commercial
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	122,859	73,562
90 Days Past Due and Still Accruing	25	3
Commercial \| Current
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	122,180	73,264
Commercial \| Total Past Due
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	679	298
Commercial \| 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	504	188
Commercial \| 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	175	110
Commercial \| Commercial and industrial loans
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	83,864	52,749
90 Days Past Due and Still Accruing	3	2
Commercial \| Commercial and industrial loans \| Current
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	83,403	52,481
Commercial \| Commercial and industrial loans \| Total Past Due
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	461	268
Commercial \| Commercial and industrial loans \| 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	322	173
Commercial \| Commercial and industrial loans \| 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	139	95
Commercial \| Commercial mortgage owner-occupied loans
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	12,260	6,142
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	12,193	6,127
Commercial \| Commercial mortgage owner-occupied loans \| Total Past Due
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	67	15
Commercial \| Commercial mortgage owner-occupied loans \| 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	58	3
Commercial \| Commercial mortgage owner-occupied loans \| 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	9	12
Commercial \| Commercial mortgage nonowner-occupied loans
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	14,883	6,086
90 Days Past Due and Still Accruing	19	0
Commercial \| Commercial mortgage nonowner-occupied loans \| Current
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	14,788	6,083
Commercial \| Commercial mortgage nonowner-occupied loans \| Total Past Due
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	95	3
Commercial \| Commercial mortgage nonowner-occupied loans \| 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	71	1
Commercial \| Commercial mortgage nonowner-occupied loans \| 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	24	2
Commercial \| Commercial construction loans
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	8,329	5,316
90 Days Past Due and Still Accruing	2	1
Commercial \| Commercial construction loans \| Current
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	8,280	5,315
Commercial \| Commercial construction loans \| Total Past Due
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	49	1
Commercial \| Commercial construction loans \| 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	47	0
Commercial \| Commercial construction loans \| 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	2	1
Commercial \| Commercial leases
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	3,523	3,269
90 Days Past Due and Still Accruing	1	0
Commercial \| Commercial leases \| Current
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	3,516	3,258
Commercial \| Commercial leases \| Total Past Due
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	7	11
Commercial \| Commercial leases \| 30 to 89 Days
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	6	11
Commercial \| Commercial leases \| 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Total portfolio loans and leases	$ 1	$ 0