v3.26.1
Financial Instruments - Amortized Cost and Fair Value of Securities Available-for-Sale (Details) - USD ($)
$ in Thousands
Jun. 30, 2026
Dec. 31, 2025
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value $ 2,776,216 $ 2,871,931
U.S. government-sponsored enterprises    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 204,386 240,782
U.S. government-sponsored mortgage-backed securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 1,159,938 1,212,948
Private mortgage-backed securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 167,761 145,720
Non-government-sponsored asset backed securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 96,881 157,844
State and political subdivisions    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 905,333 887,838
Other securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 241,917 226,799
Fair Value, Recurring    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 2,776,216 2,871,931
Fair Value, Recurring | Level 1    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 0 0
Fair Value, Recurring | Level 2    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 2,741,530 2,841,820
Fair Value, Recurring | Level 3    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 34,686 30,111
Fair Value, Recurring | U.S. government-sponsored enterprises    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 204,386 240,782
Fair Value, Recurring | U.S. government-sponsored enterprises | Level 1    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 0 0
Fair Value, Recurring | U.S. government-sponsored enterprises | Level 2    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 204,386 240,782
Fair Value, Recurring | U.S. government-sponsored enterprises | Level 3    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 0 0
Fair Value, Recurring | U.S. government-sponsored mortgage-backed securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 1,159,938 1,212,948
Fair Value, Recurring | U.S. government-sponsored mortgage-backed securities | Level 1    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 0 0
Fair Value, Recurring | U.S. government-sponsored mortgage-backed securities | Level 2    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 1,159,938 1,212,948
Fair Value, Recurring | U.S. government-sponsored mortgage-backed securities | Level 3    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 0 0
Fair Value, Recurring | Private mortgage-backed securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 167,761 145,720
Fair Value, Recurring | Private mortgage-backed securities | Level 1    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 0 0
Fair Value, Recurring | Private mortgage-backed securities | Level 2    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 167,761 145,720
Fair Value, Recurring | Private mortgage-backed securities | Level 3    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 0 0
Fair Value, Recurring | Non-government-sponsored asset backed securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 96,881 157,844
Fair Value, Recurring | Non-government-sponsored asset backed securities | Level 1    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 0 0
Fair Value, Recurring | Non-government-sponsored asset backed securities | Level 2    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 96,881 157,844
Fair Value, Recurring | Non-government-sponsored asset backed securities | Level 3    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 0 0
Fair Value, Recurring | State and political subdivisions    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 905,333 887,838
Fair Value, Recurring | State and political subdivisions | Level 1    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 0 0
Fair Value, Recurring | State and political subdivisions | Level 2    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 891,426 872,522
Fair Value, Recurring | State and political subdivisions | Level 3    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 13,907 15,316
Fair Value, Recurring | Other securities    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 241,917 226,799
Fair Value, Recurring | Other securities | Level 1    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 0 0
Fair Value, Recurring | Other securities | Level 2    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value 221,138 212,004
Fair Value, Recurring | Other securities | Level 3    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Estimated Fair Value $ 20,779 $ 14,795