Investments - Summary of Amortized Cost and Fair Value of Investments in Fixed Maturity Securities, Classified as Available-for-Sale (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Schedule Of Available For Sale Securities [Line Items]
Within one year, Amortized Cost	$ 17,265	$ 25,995
After one year through five years, Amortized Cost	108,489	106,178
After five years through ten years, Amortized Cost	71,967	82,664
After ten years, Amortized Cost	$ 97,070	$ 106,144
Investment, Type [Extensible Enumeration]	Mortgage-Backed Securities, Issued by US Government Sponsored Enterprises [Member]	Mortgage-Backed Securities, Issued by US Government Sponsored Enterprises [Member]
Without single maturity date, Amortized Cost	$ 4,861	$ 5,190
Available-for-sale, Amortized Cost	299,652	326,171
Within one year, Fair Value	17,071	25,875
After one year through five years, Fair Value	104,174	102,201
After five years through ten years, Fair Value	69,051	80,911
After ten years, Fair Value	92,947	103,332
Without single maturity date, Fair value	4,346	4,745
Available-for-sale, Fair Value	$ 287,589	$ 317,064