Loss and Loss Adjustment Expenses - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Unpaid Losses And Loss Expenses [Line Items]
Loss and LAE Related to Prior Periods	$ 65,002	$ 45,596	$ 34,770
Minimum period of underwriting workers’ compensation insurance from which historical loss data utilize	34 years
Accident Year 2015 [Member]
Unpaid Losses And Loss Expenses [Line Items]
Loss and LAE Related to Prior Periods	$ 14,500
Accident Year 2016 [Member]
Unpaid Losses And Loss Expenses [Line Items]
Loss and LAE Related to Prior Periods	$ 23,400