Loss and Loss Adjustment Expenses - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Unpaid Losses And Loss Expenses [Line Items]
Loss and LAE Related to Prior Periods	$ 63,484	$ 65,002	$ 45,596
Minimum period of underwriting workers’ compensation insurance from which historical loss data utilize	35 years
Accident Year 2017 [Member]
Unpaid Losses And Loss Expenses [Line Items]
Loss and LAE Related to Prior Periods	$ 14,500
Accident Year 2018 [Member]
Unpaid Losses And Loss Expenses [Line Items]
Loss and LAE Related to Prior Periods	$ 14,800