Investments - Fair Value and Amortized Cost of Debt Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Available-for-Sale, Amortized Cost, Within one year	$ 89,422
Available-for-Sale, Amortized Cost, One to five years	52,916
Available-for-Sale, Amortized Cost, Five to ten years	129,925
Available-for-Sale, Amortized Cost, After ten years	37,790
Available-for-Sale, Amortized Cost, Mortgage-backed securities	769,199
Available-for-Sale, Amortized Cost	1,079,252	$ 997,196
Available-for-Sale, Fair Value, Within one year	89,390
Available-for-Sale, Fair Value, One to five years	52,734
Available-for-Sale, Fair Value, Five to ten years	117,105
Available-for-Sale, Fair Value, After ten years	31,390
Available-for-Sale, Fair Value, Mortgage-backed securities	713,836
Available-for-Sale, Fair Value, Total debt securities	1,004,455	919,648
Held-to-Maturity, Amortized Cost, Five to ten years	172
Held-to-Maturity, Amortized Cost, After ten years	1,113
Held-to-Maturity, Amortized Cost, Mortgage-backed securities	3,932
Held-to-Maturity, Amortized Cost	5,217	2,209
Held-to-Maturity, Fair Value, Five to ten years	167
Held-to-Maturity, Fair Value, After ten years	1,138
Held-to-Maturity, Fair Value, Mortgage-backed securities	3,909
Held-to-Maturity, Fair Value, Total debt securities	$ 5,214	$ 2,250