Fair Value Measurements - Summary of Carrying Amounts and Corresponding Fair Values for Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities-held-to-maturity	$ 463,814	$ 468,144
Fixed maturity securities-available-for-sale	345,088	321,121
Equity securities	63,357	62,058
Short-term investments	31,269	14,120
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities-held-to-maturity	480,142	491,688
Fixed maturity securities-available-for-sale	345,088	321,121
Equity securities	63,357	62,058
Short-term investments	31,269	14,120
Cash and cash equivalents	41,210	61,469
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities-held-to-maturity	463,814	468,144
Fixed maturity securities-available-for-sale	345,088	321,121
Equity securities	63,357	62,058
Short-term investments	31,269	14,120
Cash and cash equivalents	$ 41,210	$ 61,469