Securities - Summary of Amortized Cost and Estimated Fair Values of Debt Securities Available for Sale (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 1,264,397	$ 528,689
Gross Unrealized Gains	456	4,625
Gross Unrealized Losses	(61,350)	(1,791)
Estimated Fair Value	1,203,503	531,523
U.S. Treasuries [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,205,842	455,701
Gross Unrealized Gains	3	3,693
Gross Unrealized Losses	(58,987)	(1,766)
Estimated Fair Value	1,146,858	457,628
U.S. Federal Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	18,509	21,609
Gross Unrealized Gains	363	335
Gross Unrealized Losses	(1)	(2)
Estimated Fair Value	18,871	21,942
Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	18,689	28,897
Gross Unrealized Gains	29	400
Gross Unrealized Losses	(1,429)	(14)
Estimated Fair Value	17,289	29,283
States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,994	6,128
Gross Unrealized Gains	61	194
Gross Unrealized Losses	(179)	(3)
Estimated Fair Value	4,876	6,319
Asset backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,363	13,354
Gross Unrealized Gains		3
Gross Unrealized Losses	(486)
Estimated Fair Value	12,877	13,357
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,000	3,000
Gross Unrealized Losses	(268)	(6)
Estimated Fair Value	$ 2,732	$ 2,994