Investments - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2022 USD ($) Security	Dec. 31, 2021 USD ($)
Marketable Securities [Line Items]
Individual fixed maturity held in unrealized loss position | Security	185
Individual fixed maturity held in unrealized loss position longer than 12 months | Security	48
Number of fixed maturity securities, allowance for credit loss | Security	464
Fixed maturity securities, held-to-maturity, allowance for credit losses	$ 239,000	$ 195,000
Available-for-sale, Allowance for Credit Losses	0	0
Held-to-Maturity Securities [Member]
Marketable Securities [Line Items]
Investments on deposit with regulatory agencies	24,000,000.0
Corporate Bonds [Member]
Marketable Securities [Line Items]
Short-term investments	9,900,000	55,800,000
Fixed maturity securities, held-to-maturity, allowance for credit losses	$ 196,000	143,000
Number of majority securities | Security	22
States and Political Subdivisions [Member]
Marketable Securities [Line Items]
Short-term investments	$ 1,200,000	1,600,000
Fixed maturity securities, held-to-maturity, allowance for credit losses	$ 40,000	$ 48,000
Number of majority securities | Security	439
U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member]
Marketable Securities [Line Items]
Short-term investments	$ 3,000,000.0
Corporate Fixed Income Securities [Member] | Maximum [Member]
Marketable Securities [Line Items]
Investments maturity period using default rate	20 years