v3.26.1
Fair Value of Assets and Liabilities - Schedule of The Balances Of Assets And Liabilities Measured At Fair Value On A Recurring Basis (Details) - USD ($)
$ in Thousands
Jun. 30, 2026
Dec. 31, 2025
Assets    
Securities available for sale: $ 4,047,828 $ 3,825,569
Derivative asset 51,806 55,048
Liabilities    
Derivative liability 75,512 74,719
Government-sponsored residential mortgage-backed securities    
Assets    
Securities available for sale: 2,794,837 2,533,309
Government-sponsored commercial mortgage-backed securities    
Assets    
Securities available for sale: 1,024,510 1,060,331
U.S. Treasury securities    
Assets    
Securities available for sale: 50,066 50,350
Fair Value, Recurring    
Assets    
Investments for employee retirement benefits 110,648 106,534
Deferred compensation investments 2,354 2,384
Loans held for sale 42,649 22,761
Mortgage servicing rights 39,642 40,709
Total 4,295,328 4,053,463
Liabilities    
Total 75,578 74,819
Fair Value, Recurring | Risk participation agreements    
Assets    
Derivative asset 8 10
Liabilities    
Derivative liability 6 7
Fair Value, Recurring | Foreign currency exchange contracts - matched customer book    
Assets    
Derivative asset 1,358 434
Liabilities    
Derivative liability 1,318 330
Fair Value, Recurring | Foreign currency exchange contracts - foreign currency loan    
Assets    
Derivative asset 13 13
Liabilities    
Derivative liability 8  
Fair Value, Recurring | Mortgage Derivative    
Assets    
Derivative asset 401 458
Liabilities    
Derivative liability 66 100
Fair Value, Recurring | Designated as Hedging Instrument | Interest rate swaps    
Assets    
Derivative asset 1 30
Liabilities    
Derivative liability 55 24
Fair Value, Recurring | Not Designated as Hedging Instrument | Interest rate swaps    
Assets    
Derivative asset 50,426 54,561
Liabilities    
Derivative liability 74,125 74,358
Fair Value, Recurring | Government-sponsored residential mortgage-backed securities    
Assets    
Securities available for sale: 2,794,837 2,533,309
Fair Value, Recurring | Government-sponsored commercial mortgage-backed securities    
Assets    
Securities available for sale: 1,024,510 1,060,331
Fair Value, Recurring | U.S. Treasury securities    
Assets    
Securities available for sale: 50,066 50,350
Fair Value, Recurring | State and municipal bonds and obligations    
Assets    
Securities available for sale: 178,415 181,579
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)    
Assets    
Investments for employee retirement benefits 95,488 94,736
Deferred compensation investments 2,354 2,384
Loans held for sale 0 0
Mortgage servicing rights 0 0
Total 147,908 147,470
Liabilities    
Total 0 0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Risk participation agreements    
Assets    
Derivative asset 0 0
Liabilities    
Derivative liability 0 0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign currency exchange contracts - matched customer book    
Assets    
Derivative asset 0 0
Liabilities    
Derivative liability 0 0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign currency exchange contracts - foreign currency loan    
Assets    
Derivative asset 0 0
Liabilities    
Derivative liability 0  
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Mortgage Derivative    
Assets    
Derivative asset 0 0
Liabilities    
Derivative liability 0 0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Designated as Hedging Instrument | Interest rate swaps    
Assets    
Derivative asset 0 0
Liabilities    
Derivative liability 0 0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Not Designated as Hedging Instrument | Interest rate swaps    
Assets    
Derivative asset 0 0
Liabilities    
Derivative liability 0 0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Government-sponsored residential mortgage-backed securities    
Assets    
Securities available for sale: 0 0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Government-sponsored commercial mortgage-backed securities    
Assets    
Securities available for sale: 0 0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Treasury securities    
Assets    
Securities available for sale: 50,066 50,350
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | State and municipal bonds and obligations    
Assets    
Securities available for sale: 0 0
Fair Value, Recurring | Significant Other Observable Inputs (Level 2)    
Assets    
Investments for employee retirement benefits 15,160 11,798
Deferred compensation investments 0 0
Loans held for sale 42,649 22,761
Mortgage servicing rights 0 0
Total 4,107,778 3,865,284
Liabilities    
Total 75,578 74,819
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Risk participation agreements    
Assets    
Derivative asset 8 10
Liabilities    
Derivative liability 6 7
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Foreign currency exchange contracts - matched customer book    
Assets    
Derivative asset 1,358 434
Liabilities    
Derivative liability 1,318 330
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Foreign currency exchange contracts - foreign currency loan    
Assets    
Derivative asset 13 13
Liabilities    
Derivative liability 8  
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Mortgage Derivative    
Assets    
Derivative asset 401 458
Liabilities    
Derivative liability 66 100
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Designated as Hedging Instrument | Interest rate swaps    
Assets    
Derivative asset 1 30
Liabilities    
Derivative liability 55 24
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Not Designated as Hedging Instrument | Interest rate swaps    
Assets    
Derivative asset 50,426 54,561
Liabilities    
Derivative liability 74,125 74,358
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Government-sponsored residential mortgage-backed securities    
Assets    
Securities available for sale: 2,794,837 2,533,309
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Government-sponsored commercial mortgage-backed securities    
Assets    
Securities available for sale: 1,024,510 1,060,331
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | U.S. Treasury securities    
Assets    
Securities available for sale: 0 0
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | State and municipal bonds and obligations    
Assets    
Securities available for sale: 178,415 181,579
Fair Value, Recurring | Significant Unobservable Inputs (Level 3)    
Assets    
Investments for employee retirement benefits 0 0
Deferred compensation investments 0 0
Loans held for sale 0 0
Mortgage servicing rights 39,642 40,709
Total 39,642 40,709
Liabilities    
Total 0 0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | Risk participation agreements    
Assets    
Derivative asset 0 0
Liabilities    
Derivative liability 0 0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | Foreign currency exchange contracts - matched customer book    
Assets    
Derivative asset 0 0
Liabilities    
Derivative liability 0 0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | Foreign currency exchange contracts - foreign currency loan    
Assets    
Derivative asset 0 0
Liabilities    
Derivative liability 0  
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | Mortgage Derivative    
Assets    
Derivative asset 0 0
Liabilities    
Derivative liability 0 0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | Designated as Hedging Instrument | Interest rate swaps    
Assets    
Derivative asset 0 0
Liabilities    
Derivative liability 0 0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | Not Designated as Hedging Instrument | Interest rate swaps    
Assets    
Derivative asset 0 0
Liabilities    
Derivative liability 0 0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | Government-sponsored residential mortgage-backed securities    
Assets    
Securities available for sale: 0 0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | Government-sponsored commercial mortgage-backed securities    
Assets    
Securities available for sale: 0 0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | U.S. Treasury securities    
Assets    
Securities available for sale: 0 0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | State and municipal bonds and obligations    
Assets    
Securities available for sale: $ 0 $ 0