Securities - Maturity of Debt Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Held for Investment, Contractual maturity of debt securities, Amortized Cost
Amortized cost, Within one year	$ 581	$ 577
Amortized cost, After one year but within five years	2,332	2,396
Amortized cost, After five years but within ten years	4	4
Amortized Cost	2,917	2,977
Available for sale, Contractual maturity of debt securities, Amortized Cost
Amortized Cost, Within one year	52,902	58,478
Amortized Cost, After one year but within five years	956,577	408,253
Amortized Cost, After five years but within ten years	189,828	10,851
Amortized Cost, After ten years	48,126	51,107
Amortized Cost	1,247,433	528,689
Held for Investment, Contractual maturity of debt securities, Estimated Fair Value
Estimated Fair Value, Within one year	581	577
Estimated Fair Value, After one year but within five years	2,332	2,397
Estimated Fair Value, After five years but within ten years	4	4
Estimated Fair Value	2,917	2,978
Available for sale, Contractual maturity of debt securities, Estimated Fair Value
Estimated Fair Value, Within one year	53,213	58,688
Estimated Fair Value, After one year but within five years	917,966	410,049
Estimated Fair Value, After five years but within ten years	190,010	11,011
Estimated Fair Value, After ten years	47,562	51,775
Total debt securities	$ 1,208,751	$ 531,523