Investments - Major Categories of the Company's Net Investment Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Total gross investment income	$ 32,269	$ 28,225	$ 26,422
Investment expenses	(930)	(1,002)	(987)
Net investment income	31,339	27,223	25,435
Fixed Maturity Securities Available for Sale [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Total gross investment income	26,357	24,399	24,882
Equity Securities [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Total gross investment income	1,456	1,566	1,236
Short-term Investments [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Total gross investment income	$ 4,456	$ 2,260	$ 304