Commitments and Contingencies - Financial Instruments with Off-Balance-Sheet Risk (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Standby Letters of Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments with off- balance-sheet risk	$ 433,399	$ 438,635
Deferred Standby Letter Of Credit Fees [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments with off- balance-sheet risk	2,354	2,912
Commitments to Extend Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Financial instruments with off- balance-sheet risk	$ 12,161,223	$ 12,195,073