Securities - Maturity of Debt Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Held for Investment, Contractual maturity of debt securities, Amortized Cost
Amortized cost, Within one year	$ 560	$ 776
Amortized cost, After one year but within five years	1	61
Amortized Cost	561	837
Available for sale, Contractual maturity of debt securities, Amortized Cost
Amortized Cost, Within one year	340,445	335,108
Amortized Cost, After one year but within five years	757,598	888,721
Amortized Cost, After five years but within ten years	13,414	13,369
Amortized Cost, After ten years	15,591	16,770
Amortized Cost	1,127,048	1,253,968
Held for Investment, Contractual maturity of debt securities, Estimated Fair Value
Estimated Fair Value, Within one year	560	776
Estimated Fair Value, After one year but within five years	1	61
Estimated Fair Value	561	837
Available for sale, Contractual maturity of debt securities, Estimated Fair Value
Estimated Fair Value, Within one year	336,476	330,076
Estimated Fair Value, After one year but within five years	741,045	853,508
Estimated Fair Value, After five years but within ten years	12,423	12,354
Estimated Fair Value, After ten years	14,099	14,979
Total debt securities	$ 1,104,043	$ 1,210,917