Investments - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($) Security	Dec. 31, 2020 USD ($)
Marketable Securities [Line Items]
Individual fixed maturity held in unrealized loss position | Security	42
Individual fixed maturity held in unrealized loss position longer than 12 months | Security	0
Number of fixed maturity securities, allowance for credit loss | Security	372
Fixed maturity securities, allowance for credit loss	$ 195	$ 274
Held-to-Maturity Securities [Member]
Marketable Securities [Line Items]
Investments on deposit with regulatory agencies	23,200
Corporate Bonds [Member]
Marketable Securities [Line Items]
Short-term investments	55,800	6,100
Fixed maturity securities, allowance for credit loss	$ 143	225
Number of majority securities | Security	347
States and Political Subdivisions [Member]
Marketable Securities [Line Items]
Short-term investments	$ 1,600	9,100
Fixed maturity securities, allowance for credit loss	$ 48	42
Number of majority securities | Security	22
U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member]
Marketable Securities [Line Items]
Short-term investments	$ 55,800	$ 30,700
Corporate Fixed Income Securities [Member] | Maximum [Member]
Marketable Securities [Line Items]
Investments maturity period using default rate	20 years