Securities - Summary of Amortized Cost and Estimated Fair Values of Debt Securities Available for Sale (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 1,626,938	$ 528,689
Gross Unrealized Gains	266	4,625
Gross Unrealized Losses	(107,945)	(1,791)
Estimated Fair Value	1,519,259	531,523
U.S. Treasuries [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,563,520	455,701
Gross Unrealized Gains		3,693
Gross Unrealized Losses	(104,430)	(1,766)
Estimated Fair Value	1,459,090	457,628
U.S. Federal Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	16,353	21,609
Gross Unrealized Gains	229	335
Gross Unrealized Losses	(5)	(2)
Estimated Fair Value	16,577	21,942
Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	17,866	28,897
Gross Unrealized Gains	13	400
Gross Unrealized Losses	(2,259)	(14)
Estimated Fair Value	15,620	29,283
States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	7,832	6,128
Gross Unrealized Gains	24	194
Gross Unrealized Losses	(256)	(3)
Estimated Fair Value	7,600	6,319
Asset backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,367	13,354
Gross Unrealized Gains		3
Gross Unrealized Losses	(399)
Estimated Fair Value	12,968	13,357
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	8,000	3,000
Gross Unrealized Losses	(596)	(6)
Estimated Fair Value	$ 7,404	$ 2,994