Fair Value Measurements - Summary of Carrying Amounts and Corresponding Fair Values for Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities-held-to-maturity	$ 452,019	$ 468,144
Fixed maturity securities-available-for-sale	306,040	321,121
Equity securities	54,926	62,058
Short-term investments	40,887	14,120
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities-held-to-maturity	487,166	491,688
Fixed maturity securities-available-for-sale	306,040	321,121
Equity securities	54,926	62,058
Short-term investments	40,887	14,120
Cash and cash equivalents	59,249	61,469
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities-held-to-maturity	452,019	468,144
Fixed maturity securities-available-for-sale	306,040	321,121
Equity securities	54,926	62,058
Short-term investments	40,887	14,120
Cash and cash equivalents	$ 59,249	$ 61,469