Investment Securities - Analysis of Amortized Cost and Estimated Fair Values of Securities Available for Sale (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Investment Securities [Line Items]
Amortized Cost	$ 926,875	$ 1,045,579
Gross Unrealized Gains	250	9,515
Gross Unrealized Losses	(139,710)	(13,714)
Debt Securities, Available-for-Sale	787,415	1,041,380
US Government Agencies Residential Mortgage-backed Securities [Member]
Investment Securities [Line Items]
Amortized Cost	4,456	5,242
Gross Unrealized Gains	65	420
Gross Unrealized Losses	(232)	0
Debt Securities, Available-for-Sale	4,289	5,662
US Government Agency Debt Securities Commercial [Member]
Investment Securities [Line Items]
Amortized Cost	334,730	365,024
Gross Unrealized Gains	0	1,725
Gross Unrealized Losses	(51,477)	(4,459)
Debt Securities, Available-for-Sale	283,253	362,290
Residential Mortgage Backed Securities [Member]
Investment Securities [Line Items]
Amortized Cost	545,165	632,687
Gross Unrealized Gains	24	6,308
Gross Unrealized Losses	(83,676)	(9,021)
Debt Securities, Available-for-Sale	461,513	629,974
US Government-sponsored Enterprises Debt Securities [Member]
Investment Securities [Line Items]
Amortized Cost	1,000	1,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(127)	(19)
Debt Securities, Available-for-Sale	873	981
Obligations of States and Political Subdivisions [Member]
Investment Securities [Line Items]
Amortized Cost	9,494	9,538
Gross Unrealized Gains	0	89
Gross Unrealized Losses	(1,322)	(103)
Debt Securities, Available-for-Sale	8,172	9,524
Corporate Debt Securities [Member]
Investment Securities [Line Items]
Amortized Cost	32,030	32,088
Gross Unrealized Gains	161	973
Gross Unrealized Losses	(2,876)	(112)
Debt Securities, Available-for-Sale	$ 29,315	$ 32,949