Comprehensive Income and Accumulated Other Comprehensive Loss - Reclassification Out of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net realized gains (losses) on investments		$ 158	$ 3,118	$ (181)
Income before income taxes	$ 17,481	17,793	46,157	52,282
Income tax expense	(3,663)	(3,469)	(9,435)	(10,040)
Net income	13,818	14,324	36,722	42,242
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	(86)	37	(545)	(136)
Income before income taxes	(86)	37	(545)	(136)
Income tax expense	18	(8)	115	28
Net income	$ (68)	$ 29	$ (430)	$ (108)