Comprehensive Income and Accumulated Other Comprehensive Loss - Reclassification Out of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net realized gains (losses) on investments	$ 3,034	$ (576)	$ 6,579
Income before income taxes	58,851	69,056	77,377
Income tax expense	(11,706)	(13,620)	(15,269)
Net income	47,145	55,436	62,108
Unrealized losses on Available-for-Sale Securities [Member] | Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net realized gains (losses) on investments	(396)	(302)	(547)
Income before income taxes	(396)	(302)	(547)
Income tax expense	83	64	115
Net income	$ (313)	$ (238)	$ (432)