Investments - Carrying Value of Securities Pledged as Collateral to Secure Public Fund Deposits (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Debt Securities, Available-for-Sale [Line Items]
Carrying value of securities pledged as collateral	$ 836,332	$ 748,970
Book Value	894,986	803,361
Fair Value	836,332	748,970
Public Fund Deposits [Member]
Debt Securities, Available-for-Sale [Line Items]
Carrying value of securities pledged as collateral	691,028	488,270
Book Value	728,979	509,010
Fair Value	691,028	488,270
Federal Home Loan Bank Pledging [Member]
Debt Securities, Available-for-Sale [Line Items]
Carrying value of securities pledged as collateral	93,337	72,293
Book Value	109,856	84,421
Fair Value	93,337	72,293
Federal Reserve Bank Borrowings [Member]
Debt Securities, Available-for-Sale [Line Items]
Carrying value of securities pledged as collateral	11,763	141,125
Book Value	12,119	158,382
Fair Value	11,763	141,125
Retail Repurchase Agreements [Member]
Debt Securities, Available-for-Sale [Line Items]
Carrying value of securities pledged as collateral	40,204	47,282
Book Value	44,032	51,548
Fair Value	$ 40,204	$ 47,282