v3.26.1
Investments - Carrying Value of Securities Pledged as Collateral to Secure Public Fund Deposits (Detail) - USD ($)
$ in Thousands
Mar. 31, 2026
Dec. 31, 2025
Debt Securities, Available-for-Sale [Line Items]    
Book Value $ 768,579 $ 828,100
Fair Value 771,156 836,537
Public Fund Deposits [Member]    
Debt Securities, Available-for-Sale [Line Items]    
Book Value 728,693 785,200
Fair Value 730,822 793,014
Federal Reserve Bank Borrowings [Member]    
Debt Securities, Available-for-Sale [Line Items]    
Book Value 501 2,002
Fair Value 508 2,042
Retail Repurchase Agreements [Member]    
Debt Securities, Available-for-Sale [Line Items]    
Book Value 39,385 40,898
Fair Value $ 39,826 $ 41,481