Loss and Loss Adjustment Expenses - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Unpaid Losses And Loss Expenses [Line Items]
Loss and LAE Related to Prior Periods	$ 45,596	$ 34,770	$ 51,306
Accident Year 2014 [Member]
Unpaid Losses And Loss Expenses [Line Items]
Loss and LAE Related to Prior Periods	8,100
Accident Year 2015 [Member]
Unpaid Losses And Loss Expenses [Line Items]
Loss and LAE Related to Prior Periods	17,000
Accident Year 2016 [Member]
Unpaid Losses And Loss Expenses [Line Items]
Loss and LAE Related to Prior Periods	$ 9,100