Securities - Summary of Amortized Cost and Estimated Fair Values of Debt Securities Available for Sale (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 1,247,433	$ 528,689
Gross Unrealized Gains	1,452	4,625
Gross Unrealized Losses	(40,134)	(1,791)
Estimated Fair Value	1,208,751	531,523
U.S. Treasuries [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,184,289	455,701
Gross Unrealized Gains	1,005	3,693
Gross Unrealized Losses	(38,996)	(1,766)
Estimated Fair Value	1,146,298	457,628
U.S. Federal Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	20,216	21,609
Gross Unrealized Gains	320	335
Gross Unrealized Losses	(2)	(2)
Estimated Fair Value	20,534	21,942
Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	21,708	28,897
Gross Unrealized Gains	51	400
Gross Unrealized Losses	(798)	(14)
Estimated Fair Value	20,961	29,283
States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,861	6,128
Gross Unrealized Gains	76	194
Gross Unrealized Losses	(85)	(3)
Estimated Fair Value	4,852	6,319
Asset backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,359	13,354
Gross Unrealized Gains		3
Gross Unrealized Losses	(79)
Estimated Fair Value	13,280	13,357
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,000	3,000
Gross Unrealized Losses	(174)	(6)
Estimated Fair Value	$ 2,826	$ 2,994