Investments - Summary of Amortized Cost and Fair Value of Investments in Fixed Maturity Securities, Classified as Available-for-Sale (Detail) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Schedule Of Available For Sale Securities [Line Items]
Within one year, Amortized Cost	$ 29,594	$ 23,944
After one year through five years, Amortized Cost	86,600	97,996
After five years through ten years, Amortized Cost	73,902	71,233
After ten years, Amortized Cost	$ 125,062	$ 121,257
Investment, Type [Extensible Enumeration]	Mortgage-Backed Security, Issued by US Government-Sponsored Enterprise [Member]	Mortgage-Backed Security, Issued by US Government-Sponsored Enterprise [Member]
Without single maturity date, Amortized Cost	$ 4,097	$ 4,545
Available-for-sale, Amortized Cost	319,255	318,975
Within one year, Fair Value	29,404	23,806
After one year through five years, Fair Value	86,290	95,500
After five years through ten years, Fair Value	73,265	68,494
After ten years, Fair Value	121,885	115,891
Without single maturity date, Fair value	3,760	4,059
Available-for-sale, Fair Value	$ 314,604	$ 307,750