Investments - Major Categories of the Company's Net Investment Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Total gross investment income	$ 28,225	$ 26,422	$ 30,317
Investment expenses	(1,002)	(987)	(953)
Net investment income	27,223	25,435	29,364
Fixed Maturity Securities Available for Sale [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Total gross investment income	24,399	24,882	28,414
Equity Securities [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Total gross investment income	1,566	1,236	1,006
Short-term Investments [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Total gross investment income	$ 2,260	$ 304	$ 897