Investments - Summary of Net Investment Income (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Investment [Line Items]
Investment expense									$ (365)	$ (296)	$ (139)
Interest Income, Debt Securities, Available-for-Sale, Operating									14,563	12,687	4,369
Net investment income	$ 3,557	$ 3,488	$ 3,763	$ 3,640	$ 3,588	$ 3,663	$ 3,027	$ 2,881	14,448	13,159	4,503
Fixed income securities										3,696	2,163
Available-for-sale Securities [Member]
Investment [Line Items]
Fixed income securities									4,895
Short-term Investments [Member]
Investment [Line Items]
Fixed income securities									10,033	9,287	2,345
Other Investments [Member]
Investment [Line Items]
Fixed income securities									(115)	472	134
Debt Securities, Trading
Investment [Line Items]
Fixed income securities									$ 0	$ 0	$ 0