Investments - Scheduled Contractual Maturities of Fixed-Maturity Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Investments, Debt and Equity Securities [Abstract]
Due in one year or less, Cost or Amortized Cost	$ 357,645	$ 266,170
Due after one year through five years, Cost or Amortized Cost	170,850	223,153
Due after five years through ten years, Cost or Amortized Cost	2,910	4,380
Due after ten years, Cost or Amortized Cost	494	494
Fixed-maturity securities, Cost or Amortized Cost	531,899	494,197
Due in one year or less, Estimated Fair Value	355,922	265,353
Due after one year through five years, Estimated Fair Value	165,769	214,307
Due after five years through ten years, Estimated Fair Value	2,583	3,797
Due after ten years, Estimated Fair Value	482	444
Estimated Fair Value Total	$ 524,756	$ 483,901