Investment Securities - Analysis of Amortized Cost and Estimated Fair Values of Securities Available for Sale (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Investment Securities [Line Items]
Amortized Cost	$ 956,870	$ 1,045,579
Gross Unrealized Gains	491	9,515
Gross Unrealized Losses	(93,739)	(13,714)
Debt Securities, Available-for-Sale	863,622	1,041,380
US Government Agencies Residential Mortgage-backed Securities [Member]
Investment Securities [Line Items]
Amortized Cost	4,644	5,242
Gross Unrealized Gains	136	420
Gross Unrealized Losses	(86)	0
Debt Securities, Available-for-Sale	4,694	5,662
US Government Agency Debt Securities Commercial [Member]
Investment Securities [Line Items]
Amortized Cost	342,766	365,024
Gross Unrealized Gains	0	1,725
Gross Unrealized Losses	(33,896)	(4,459)
Debt Securities, Available-for-Sale	308,870	362,290
Residential Mortgage Backed Securities [Member]
Investment Securities [Line Items]
Amortized Cost	566,914	632,687
Gross Unrealized Gains	191	6,308
Gross Unrealized Losses	(57,575)	(9,021)
Debt Securities, Available-for-Sale	509,530	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	(81)	(19)
Debt Securities, Available-for-Sale	919	981
Obligations of States and Political Subdivisions [Member]
Investment Securities [Line Items]
Amortized Cost	9,497	9,538
Gross Unrealized Gains	1	89
Gross Unrealized Losses	(907)	(103)
Debt Securities, Available-for-Sale	8,591	9,524
Corporate Debt Securities [Member]
Investment Securities [Line Items]
Amortized Cost	32,049	32,088
Gross Unrealized Gains	163	973
Gross Unrealized Losses	(1,194)	(112)
Debt Securities, Available-for-Sale	$ 31,018	$ 32,949