Comprehensive Income and Accumulated Other Comprehensive Loss - Reclassification Out of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net realized gains (losses) on investments	$ (222)	$ 258
Income before income taxes	20,745	21,535
Income tax expense	(3,820)	(4,196)
Net income	16,925	17,339
Unrealized Gains (Losses) On Debt Securities, Net Of Tax [Member] | Reclassification Out of Accumulated Other Comprehensive Loss [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net realized gains (losses) on investments	(115)	(6)
Income before income taxes	(115)	(6)
Income tax expense	24	1
Net income	$ (91)	$ (5)