v3.26.1
Investments - Carrying Value of Securities Pledged as Collateral to Secure Public Fund Deposits (Detail) - USD ($)
$ in Thousands
Jun. 30, 2026
Dec. 31, 2025
Debt Securities, Available-for-Sale [Line Items]    
Book Value $ 772,803 $ 828,100
Fair Value 770,708 836,537
Public Fund Deposits [Member]    
Debt Securities, Available-for-Sale [Line Items]    
Book Value 727,061 785,200
Fair Value 724,934 793,014
Federal Reserve Bank Borrowings [Member]    
Debt Securities, Available-for-Sale [Line Items]    
Book Value 982 2,002
Fair Value 993 2,042
Retail Repurchase Agreements [Member]    
Debt Securities, Available-for-Sale [Line Items]    
Book Value 44,760 40,898
Fair Value $ 44,781 $ 41,481