Investment Securities - Analysis of Amortized Cost and Estimated Fair Values of Securities Available for Sale (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Investment Securities [Line Items]
Amortized Cost	$ 1,151,024	$ 1,138,425
Gross Unrealized Gains	3,426	8,182
Gross Unrealized Losses	(130,739)	(125,621)
Debt Securities, Available-for-Sale	1,023,711	1,020,986
US Government Agencies Residential Mortgage-backed Securities [Member]
Investment Securities [Line Items]
Amortized Cost	3,439	3,565
Gross Unrealized Gains	25	47
Gross Unrealized Losses	(183)	(147)
Debt Securities, Available-for-Sale	3,281	3,465
US Government Agency Debt Securities Commercial [Member]
Investment Securities [Line Items]
Amortized Cost	526,472	512,979
Gross Unrealized Gains	1,968	4,935
Gross Unrealized Losses	(54,239)	(52,521)
Debt Securities, Available-for-Sale	474,201	465,393
Residential Mortgage Backed Securities [Member]
Investment Securities [Line Items]
Amortized Cost	543,883	559,769
Gross Unrealized Gains	911	3,052
Gross Unrealized Losses	(70,590)	(68,222)
Debt Securities, Available-for-Sale	474,204	494,599
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	(87)	(85)
Debt Securities, Available-for-Sale	913	915
Obligations of States and Political Subdivisions [Member]
Investment Securities [Line Items]
Amortized Cost	9,223	9,226
Gross Unrealized Gains	0	3
Gross Unrealized Losses	(1,048)	(1,027)
Debt Securities, Available-for-Sale	8,175	8,202
Corporate Debt Securities [Member]
Investment Securities [Line Items]
Amortized Cost	67,007	51,886
Gross Unrealized Gains	522	145
Gross Unrealized Losses	(4,592)	(3,619)
Debt Securities, Available-for-Sale	$ 62,937	$ 48,412