Securities - Maturity of Debt Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Held for Investment, Contractual maturity of debt securities, Amortized Cost
Amortized cost, Within one year	$ 1,187	$ 577
Amortized cost, After one year but within five years	1,197	2,396
Amortized cost, After five years but within ten years	2	4
Amortized Cost	2,386	2,977
Available for sale, Contractual maturity of debt securities, Amortized Cost
Amortized Cost, Within one year	96,447	58,478
Amortized Cost, After one year but within five years	1,260,280	408,253
Amortized Cost, After five years but within ten years	226,894	10,851
Amortized Cost, After ten years	43,317	51,107
Amortized Cost	1,626,938	528,689
Held for Investment, Contractual maturity of debt securities, Estimated Fair Value
Estimated Fair Value, Within one year	1,187	577
Estimated Fair Value, After one year but within five years	1,197	2,397
Estimated Fair Value, After five years but within ten years	2	4
Estimated Fair Value	2,386	2,978
Available for sale, Contractual maturity of debt securities, Estimated Fair Value
Estimated Fair Value, Within one year	95,552	58,688
Estimated Fair Value, After one year but within five years	1,172,140	410,049
Estimated Fair Value, After five years but within ten years	211,100	11,011
Estimated Fair Value, After ten years	40,467	51,775
Total debt securities	$ 1,519,259	$ 531,523