Fair Value of Assets and Liabilities - Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	$ 1,812	$ 1,904
Loans held for sale (elected fair value)	167	151
Total securities available for sale	8,146	8,165
Government agency issued MBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total securities available for sale	3,525	3,641
Government agency issued CMO
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total securities available for sale	2,792	2,869
States and municipalities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total securities available for sale	329	338
Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	1,812	1,904
Loans held for sale (elected fair value)	167	151
Total securities available for sale	8,146	8,165
Total other assets	459	474
Total assets	10,584	10,694
Total trading liabilities	666	607
Total other liabilities	414	402
Total liabilities	1,080	1,009
Recurring | Derivatives, forwards and futures
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other liabilities	19	9
Recurring | Derivatives, interest rate contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other liabilities	377	368
Recurring | Derivatives, other
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other liabilities	18	25
Recurring | Deferred compensation mutual funds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	106	110
Recurring | Equity, mutual funds, and other
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	17	37
Recurring | Derivatives, forwards and futures
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	26	7
Recurring | Derivatives, interest rate contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	310	320
Recurring | U.S. treasuries
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	7	8
Total trading liabilities	580	492
Recurring | Government agency issued MBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	296	352
Total securities available for sale	3,525	3,641
Recurring | Government agency issued CMO
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	406	326
Total securities available for sale	2,792	2,869
Recurring | Other U.S. government agencies
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	317	157
Total securities available for sale	1,500	1,317
Recurring | States and municipalities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	35	86
Total securities available for sale	329	338
Recurring | Corporate and other debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	710	930
Total trading liabilities	85	115
Recurring | Equity, mutual funds, and other
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	6
Total trading liabilities	1
Recurring | SBA interest-only strips
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	35	45
Level 1 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	0	0
Loans held for sale (elected fair value)	0	0
Total securities available for sale	0	0
Total other assets	149	154
Total assets	149	154
Total trading liabilities	0	0
Total other liabilities	19	9
Total liabilities	19	9
Level 1 | Recurring | Derivatives, forwards and futures
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other liabilities	19	9
Level 1 | Recurring | Derivatives, interest rate contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other liabilities	0	0
Level 1 | Recurring | Derivatives, other
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other liabilities	0	0
Level 1 | Recurring | Deferred compensation mutual funds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	106	110
Level 1 | Recurring | Equity, mutual funds, and other
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	17	37
Level 1 | Recurring | Derivatives, forwards and futures
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	26	7
Level 1 | Recurring | Derivatives, interest rate contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	0	0
Level 1 | Recurring | U.S. treasuries
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	0	0
Total trading liabilities	0	0
Level 1 | Recurring | Government agency issued MBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	0	0
Total securities available for sale	0	0
Level 1 | Recurring | Government agency issued CMO
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	0	0
Total securities available for sale	0	0
Level 1 | Recurring | Other U.S. government agencies
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	0	0
Total securities available for sale	0	0
Level 1 | Recurring | States and municipalities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	0	0
Total securities available for sale	0	0
Level 1 | Recurring | Corporate and other debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	0	0
Total trading liabilities	0	0
Level 1 | Recurring | Equity, mutual funds, and other
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	0
Total trading liabilities	0
Level 1 | Recurring | SBA interest-only strips
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	0	0
Level 2 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	1,777	1,859
Loans held for sale (elected fair value)	153	137
Total securities available for sale	8,146	8,165
Total other assets	310	320
Total assets	10,386	10,481
Total trading liabilities	666	607
Total other liabilities	377	368
Total liabilities	1,043	975
Level 2 | Recurring | Derivatives, forwards and futures
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other liabilities	0	0
Level 2 | Recurring | Derivatives, interest rate contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other liabilities	377	368
Level 2 | Recurring | Derivatives, other
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other liabilities	0	0
Level 2 | Recurring | Deferred compensation mutual funds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	0	0
Level 2 | Recurring | Equity, mutual funds, and other
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	0	0
Level 2 | Recurring | Derivatives, forwards and futures
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	0	0
Level 2 | Recurring | Derivatives, interest rate contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	310	320
Level 2 | Recurring | U.S. treasuries
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	7	8
Total trading liabilities	580	492
Level 2 | Recurring | Government agency issued MBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	296	352
Total securities available for sale	3,525	3,641
Level 2 | Recurring | Government agency issued CMO
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	406	326
Total securities available for sale	2,792	2,869
Level 2 | Recurring | Other U.S. government agencies
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	317	157
Total securities available for sale	1,500	1,317
Level 2 | Recurring | States and municipalities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	35	86
Total securities available for sale	329	338
Level 2 | Recurring | Corporate and other debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	710	930
Total trading liabilities	85	115
Level 2 | Recurring | Equity, mutual funds, and other
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	6
Total trading liabilities	1
Level 2 | Recurring | SBA interest-only strips
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	0	0
Level 3 | SBA interest-only strips
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total securities available for sale	35	45
Level 3 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	35	45
Loans held for sale (elected fair value)	14	14
Total securities available for sale	0	0
Total other assets	0	0
Total assets	49	59
Total trading liabilities	0	0
Total other liabilities	18	25
Total liabilities	18	25
Level 3 | Recurring | Derivatives, forwards and futures
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other liabilities	0	0
Level 3 | Recurring | Derivatives, interest rate contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other liabilities	0	0
Level 3 | Recurring | Derivatives, other
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other liabilities	18	25
Level 3 | Recurring | Deferred compensation mutual funds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	0	0
Level 3 | Recurring | Equity, mutual funds, and other
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	0	0
Level 3 | Recurring | Derivatives, forwards and futures
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	0	0
Level 3 | Recurring | Derivatives, interest rate contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	0	0
Level 3 | Recurring | U.S. treasuries
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	0	0
Total trading liabilities	0	0
Level 3 | Recurring | Government agency issued MBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	0	0
Total securities available for sale	0	0
Level 3 | Recurring | Government agency issued CMO
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	0	0
Total securities available for sale	0	0
Level 3 | Recurring | Other U.S. government agencies
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	0	0
Total securities available for sale	0	0
Level 3 | Recurring | States and municipalities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	0	0
Total securities available for sale	0	0
Level 3 | Recurring | Corporate and other debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	0	0
Total trading liabilities	0	0
Level 3 | Recurring | Equity, mutual funds, and other
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	0
Total trading liabilities	0
Level 3 | Recurring | SBA interest-only strips
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total trading securities	$ 35	$ 45