Investment Securities - Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Amortized Cost
Due in one year	$ 57,685
Due after one year through five years	125,533
Due after five years through ten years	418,008
Due after ten years	2,141,761
Amortized Cost	2,742,987	$ 2,208,330
Estimated Fair Value
Due in one year	56,111
Due after one year through five years	120,116
Due after five years through ten years	395,462
Due after ten years	1,880,749
Totals	2,452,438	2,207,938
Amortized Cost
Due in one year	0
Due after one year through five years	3,730
Due after five years through ten years	14,721
Due after ten years	142,532
Amortized Cost	160,983	199,759
Estimated Fair Value
Due in one year	0
Due after one year through five years	3,616
Due after five years through ten years	13,998
Due after ten years	132,324
Totals	$ 149,938	$ 208,140