Loss and Loss Adjustment Expenses - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Unpaid Losses And Loss Expenses [Line Items]
Loss and LAE Related to Prior Periods	$ (51,306)	$ (47,814)	$ (23,717)
Accident Year 2012 [Member]
Unpaid Losses And Loss Expenses [Line Items]
Loss and LAE Related to Prior Periods	9,100
Accident Year 2013 [Member]
Unpaid Losses And Loss Expenses [Line Items]
Loss and LAE Related to Prior Periods	13,200
Accident Year 2014 [Member]
Unpaid Losses And Loss Expenses [Line Items]
Loss and LAE Related to Prior Periods	$ 19,700