Losses and Loss Adjustment Expenses Incurred and Paid - Information Regarding the Reserve for Unpaid Losses and Loss Adjustment Expenses (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Insurance [Abstract]
Liability for unpaid losses and LAE at beginning of period, gross	$ 161,079	$ 122,071
Reinsurance balances receivable, beginning balance	(769)	(464)
Liability for unpaid losses and LAE at beginning of period, net	160,310	121,607
Add: Provision for losses and LAE:
Current period	56,812	63,105
Prior periods	(532)	10,314
Net losses and LAE incurred	56,280	73,419
Less: Losses and LAE paid:
Current period	16,137	18,404
Prior periods	44,806	44,463
Net losses and LAE paid	60,943	62,867
Liability for unpaid losses and LAE at end of period, net	155,647	132,159
Reinsurance balances receivable, ending balance	763	491
Liability for unpaid losses and LAE at end of period, gross	$ 156,410	$ 132,650