Investments - Additional Information (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2025 USD ($) Security	Mar. 31, 2024 USD ($)	Dec. 31, 2024 USD ($)
Marketable Securities [Line Items]
Individual fixed maturity held in unrealized loss position | Security	184
Number of fixed maturity securities, allowance for credit loss | Security	401
Fixed maturity securities, held-to-maturity, allowance for credit losses	$ 100		$ 116
Fixed maturity securities, available-for-sale, allowance for credit losses	0		0
Net realized gains (losses) on investments	2	$ (222)
Net unrealized gains (losses) on equity securities	(3,152)	$ 4,776
Corporate Bonds [Member]
Marketable Securities [Line Items]
Fixed maturity securities, held-to-maturity, allowance for credit losses	$ 71		86
Number of majority securities | Security	13
States and Political Subdivisions [Member]
Marketable Securities [Line Items]
Fixed maturity securities, held-to-maturity, allowance for credit losses	$ 29		$ 30
Number of majority securities | Security	387
Corporate Fixed Income Securities [Member] | Maximum [Member]
Marketable Securities [Line Items]
Investments maturity period using default rate	20 years