Investments - Additional Information (Detail) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023 USD ($) Security	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) Security	Sep. 30, 2022 USD ($)	Jun. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)
Marketable Securities [Line Items]
Individual fixed maturity held in unrealized loss position | Security	202		202
Number of fixed maturity securities, allowance for credit loss | Security	471		471
Fixed maturity securities, held-to-maturity, allowance for credit losses	$ 188		$ 188		$ 204	$ 239
Available-for-sale, Allowance for Credit Losses	0		0			0
Net realized gains on investments	5,133	$ 585	5,466	$ 2,402
Net unrealized gains (losses) on equity securities	(7,309)	$ (4,082)	(3,892)	$ (12,984)
Corporate Bonds [Member]
Marketable Securities [Line Items]
Fixed maturity securities, held-to-maturity, allowance for credit losses	$ 150		$ 150		161	196
Number of majority securities | Security	18		18
States and Political Subdivisions [Member]
Marketable Securities [Line Items]
Fixed maturity securities, held-to-maturity, allowance for credit losses	$ 37		$ 37		$ 41	$ 40
Number of majority securities | Security	450		450
Corporate Fixed Income Securities [Member] | Maximum [Member]
Marketable Securities [Line Items]
Investments maturity period using default rate			20 years