Fair Values of Financial Instruments - Summary of Carrying Amounts and Corresponding Fair Values for Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities, fair value	$ 364,386	$ 399,721
Fixed maturity securities-available-for-sale	314,604	307,750
Equity securities	56,568	58,629
Short-term investments	19,090	9,338
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities, fair value	372,018	413,061
Fixed maturity securities-available-for-sale	314,604	307,750
Equity securities	56,568	58,629
Short-term investments	19,090	9,338
Cash and cash equivalents	54,747	44,045
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities, fair value	364,386	399,721
Fixed maturity securities-available-for-sale	314,604	307,750
Equity securities	56,568	58,629
Short-term investments	19,090	9,338
Cash and cash equivalents	$ 54,747	$ 44,045