Investments - Additional Information (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2022 USD ($) Security	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)
Marketable Securities [Line Items]
Individual fixed maturity held in unrealized loss position | Security	107
Individual fixed maturity held in unrealized loss position longer than 12 months | Security	0
Number of fixed maturity securities, allowance for credit loss | Security	362
Fixed maturity securities, allowance for credit loss	$ 290		$ 195
Available-for-sale, Allowance for Credit Losses	0		0
Net realized gains on investments	738	$ 319
Net unrealized gains on equity securities	1,040	$ 5,511
Corporate Bonds [Member]
Marketable Securities [Line Items]
Fixed maturity securities, allowance for credit loss	$ 241		143
Number of majority securities | Security	26
States and Political Subdivisions [Member]
Marketable Securities [Line Items]
Fixed maturity securities, allowance for credit loss	$ 45		$ 48
Number of majority securities | Security	333
Corporate Fixed Income Securities [Member] | Maximum [Member]
Marketable Securities [Line Items]
Investments maturity period using default rate	20 years