Comprehensive Income (Loss) - Components of Other Comprehensive Income (Loss) and Related Tax Effects (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Accumulated Other Comprehensive Income (Loss) [Line Items]
Realized gain (loss) on debt securities andTotal amounts reclassified out of accumulated other comprehensive income (loss)	$ (4)	$ 0	$ 1,142	$ 0
Unrealized holding gains (losses) on available for sale securities, net of tax	9,008	2,852	31,106	(8,346)
Amortization of actuarial losses and Total amounts reclassified out of accumulated other comprehensive loss	(164)	(115)	(328)	(230)
Total other comprehensive income (loss)	9,008	2,852	31,106	(8,346)
Unrealized holding gains (losses) on available for sale securities before reclassifications
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrealized holding gains (losses) on available for sale securities before reclassifications	12,792	1,106	43,018	(14,793)
Realized gain (loss) on debt securities andTotal amounts reclassified out of accumulated other comprehensive income (loss)	(4)	2,945	1,142	2,945
Unrealized holding gains (losses) on available for sale securities after reclassifications	12,788	4,051	44,160	(11,848)
Tax effect	(3,780)	(1,199)	(13,054)	3,502
Unrealized holding gains (losses) on available for sale securities, net of tax	9,008	2,852	31,106	(8,346)
Unfunded status of the supplemental retirement plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Change in unfunded status of the supplemental retirement plans before reclassifications	164	115	328	230
Amortization of actuarial losses
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amortization of actuarial losses and Total amounts reclassified out of accumulated other comprehensive loss	$ (164)	$ (115)	$ (328)	$ (230)

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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