Investments - Major Categories of the Company's Net Investment Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Total gross investment income	$ 26,422	$ 30,317	$ 33,449
Investment expenses	(987)	(953)	(966)
Net investment income	25,435	29,364	32,483
Fixed Maturity Securities Available for Sale [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Total gross investment income	24,882	28,414	30,343
Equity Securities [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Total gross investment income	1,236	1,006	628
Short-term Investments [Member]
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Total gross investment income	$ 304	$ 897	$ 2,478