Losses and Loss Adjustment Reserve - Effects of Reinsurance on Premiums Written and Earned (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Written
Direct premiums	$ 591,142	$ 599,828
Assumed premiums	0	0
Ceded premiums	591,124	599,807
Net premiums	18	21
Earned
Direct premiums	592,123	610,753
Assumed premiums	0	18
Ceded premiums	592,105	610,750
Net premiums	$ 18	$ 21