Losses and Loss Adjustment Expenses Incurred and Paid - Information Regarding the Reserve for Unpaid Losses and Loss Adjustment Expenses (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Insurance [Abstract]
Liability for unpaid losses and LAE at beginning of period, gross	$ 122,071	$ 96,613
Reinsurance balances receivable, beginning balance	(464)	(362)
Liability for unpaid losses and LAE at beginning of period, net	121,607	96,251
Add: Provision for losses and LAE:
Current period	217,802	159,686
Prior periods	27,460	618
Net losses and LAE incurred	245,262	160,304
Less: Losses and LAE paid:
Current period	111,307	87,280
Prior periods	91,703	54,697
Net losses and LAE paid	203,010	141,977
Liability for unpaid losses and LAE at end of period, net	163,859	114,578
Reinsurance balances receivable, ending balance	841	431
Liability for unpaid losses and LAE at end of period, gross	$ 164,700	$ 115,009