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Investment Securities - Analysis of Amortized Cost and Estimated Fair Values of Securities Available for Sale (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Investment Securities [Line Items]
Amortized Cost	$ 1,234,213	$ 1,138,425
Gross Unrealized Gains	10,278	8,182
Gross Unrealized Losses	(103,691)	(125,621)
Debt Securities, Available-for-Sale	1,140,800	1,020,986
US Government Agencies Residential Mortgage-backed Securities [Member]
Investment Securities [Line Items]
Amortized Cost	3,209	3,565
Gross Unrealized Gains	33	47
Gross Unrealized Losses	(126)	(147)
Debt Securities, Available-for-Sale	3,116	3,465
US Government Agency Debt Securities Commercial [Member]
Investment Securities [Line Items]
Amortized Cost	724,019	512,979
Gross Unrealized Gains	6,683	4,935
Gross Unrealized Losses	(45,868)	(52,521)
Debt Securities, Available-for-Sale	684,834	465,393
Residential Mortgage Backed Securities [Member]
Investment Securities [Line Items]
Amortized Cost	434,676	559,769
Gross Unrealized Gains	2,236	3,052
Gross Unrealized Losses	(53,457)	(68,222)
Debt Securities, Available-for-Sale	383,455	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	(53)	(85)
Debt Securities, Available-for-Sale	947	915
Obligations of States and Political Subdivisions [Member]
Investment Securities [Line Items]
Amortized Cost	8,962	9,226
Gross Unrealized Gains	2	3
Gross Unrealized Losses	(785)	(1,027)
Debt Securities, Available-for-Sale	8,179	8,202
Corporate Debt Securities [Member]
Investment Securities [Line Items]
Amortized Cost	62,347	51,886
Gross Unrealized Gains	1,324	145
Gross Unrealized Losses	(3,402)	(3,619)
Debt Securities, Available-for-Sale	$ 60,269	$ 48,412

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Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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