Fair Values of Financial Instruments - Summary of Carrying or Reported Values and Corresponding Fair Values for Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities—held-to-maturity	$ 575,850	$ 621,654
Fixed maturity securities—available-for-sale	341,769	414,279
Equity securities	64,140	43,437
Short-term investments	57,431	45,898
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities—held-to-maturity	549,231	585,130
Fixed maturity securities—available-for-sale	341,769	414,279
Equity securities	64,140	43,437
Short-term investments	57,431	45,898
Cash and cash equivalents	70,722	61,757
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities—held-to-maturity	575,850	621,654
Fixed maturity securities—available-for-sale	341,769	414,279
Equity securities	64,140	43,437
Short-term investments	57,431	45,898
Cash and cash equivalents	$ 70,722	$ 61,757