Comprehensive Income and Accumulated Other Comprehensive Loss - Reclassification Out of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net realized gains (losses) on investments	$ (117)	$ 75	$ (339)	$ 333
Income before income taxes	13,744	19,568	34,489	41,103
Income tax expense	(2,751)	(3,941)	(6,571)	(8,137)
Net income	10,993	15,627	27,918	32,966
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	(58)	(189)	(174)	(195)
Income before income taxes	(58)	(189)	(174)	(195)
Income tax expense	12	40	37	41
Net income	$ (46)	$ (149)	$ (137)	$ (154)