Other Comprehensive Income (Loss) - Changes in Each Component of Accumulated Other Comprehensive Income (Loss), Net of Tax (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	$ 372,002	$ 334,835	$ 355,212
Net current-period other comprehensive income (loss)	(5,827)	10,515	(66,865)
Ending balance	388,502	372,002	334,835
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(43,024)	(52,771)	14,675
Other comprehensive income (loss) before classifications	(5,801)	9,747	(67,438)
Amounts reclassified from accumulated other comprehensive income (loss)	(26)	0	(8)
Net current-period other comprehensive income (loss)	(5,827)	9,747	(67,446)
Ending balance	(48,851)	(43,024)	(52,771)
Defined Benefit Pension Items [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(4,506)	(5,274)	(5,855)
Other comprehensive income (loss) before classifications	0	768	581
Amounts reclassified from accumulated other comprehensive income (loss)	0	0	0
Net current-period other comprehensive income (loss)	0	768	581
Ending balance	(4,506)	(4,506)	(5,274)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(47,530)	(58,045)	8,820
Other comprehensive income (loss) before classifications	(5,801)	10,515	(66,857)
Amounts reclassified from accumulated other comprehensive income (loss)	(26)	0	(8)
Net current-period other comprehensive income (loss)	(5,827)	10,515	(66,865)
Ending balance	$ (53,357)	$ (47,530)	$ (58,045)