Investments - Scheduled Contractual Maturities of Fixed-Maturity Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Investments Debt And Equity Securities [Abstract]
Due in one year or less, Amortized Cost	$ 50,836	$ 50,659
Due after one year through five years, Amortized Cost	144,989	117,826
Due after five years through ten years, Amortized Cost	8,068	11,602
Due after ten years, Amortized Cost	4,090	4,583
Fixed-maturity securities, Cost or Amortized Cost	207,983	184,670
Due in one year or less, Fair Value	51,056	50,574
Due after one year through five years, Fair Value	146,773	116,498
Due after five years through ten years, Fair Value	8,518	11,253
Due after ten years, Fair Value	4,406	4,398
Fair Value Total	$ 210,753	$ 182,723