Securities - Maturity of Debt Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Held for Investment, Contractual maturity of debt securities, Amortized Cost
Amortized cost, Within one year	$ 1,186	$ 577
Amortized cost, After one year but within five years	1,201	2,396
Amortized cost, After five years but within ten years	4	4
Amortized Cost	2,391	2,977
Available for sale, Contractual maturity of debt securities, Amortized Cost
Amortized Cost, Within one year	61,131	58,478
Amortized Cost, After one year but within five years	1,025,359	408,253
Amortized Cost, After five years but within ten years	132,089	10,851
Amortized Cost, After ten years	45,818	51,107
Amortized Cost	1,264,397	528,689
Held for Investment, Contractual maturity of debt securities, Estimated Fair Value
Estimated Fair Value, Within one year	1,186	577
Estimated Fair Value, After one year but within five years	1,202	2,397
Estimated Fair Value, After five years but within ten years	4	4
Estimated Fair Value	2,392	2,978
Available for sale, Contractual maturity of debt securities, Estimated Fair Value
Estimated Fair Value, Within one year	61,108	58,688
Estimated Fair Value, After one year but within five years	976,452	410,049
Estimated Fair Value, After five years but within ten years	121,770	11,011
Estimated Fair Value, After ten years	44,173	51,775
Total debt securities	$ 1,203,503	$ 531,523