Comprehensive Income and Accumulated Other Comprehensive Loss - Reclassification Out of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net realized gains (losses) on investments	$ 3,116	$ (117)	$ 3,118	$ (339)
Income before income taxes	17,455	13,744	28,676	34,489
Income tax expense	(3,500)	(2,751)	(5,772)	(6,571)
Net income	13,955	10,993	22,904	27,918
Unrealized 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	(453)	(58)	(459)	(174)
Income before income taxes	(453)	(58)	(459)	(174)
Income tax expense	95	12	96	37
Net income	$ (358)	$ (46)	$ (363)	$ (137)