Losses and Loss Adjustment Expenses Incurred and Paid - Information Regarding the Reserve for Unpaid Losses and Loss Adjustment Expenses (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Insurance [Abstract]
Liability for unpaid losses and LAE at beginning of year, gross	$ 122,071	$ 96,613	$ 84,286
Reinsurance balances receivable, beginning balance	(464)	(362)	(305)
Liability for unpaid losses and LAE at beginning of year, net	121,607	96,251	83,981
Add: Provision for losses and LAE:
Current year	278,366	218,186	166,179
Prior year	30,636	845	(4,877)
Net losses and LAE incurred	309,002	219,031	161,302
Less: Losses and LAE paid:
Current year	163,792	129,216	98,437
Prior year	106,507	64,459	50,595
Net losses and LAE paid	270,299	193,675	149,032
Liability for unpaid losses and LAE at end of year, net	160,310	121,607	96,251
Reinsurance balances receivable, ending balance	769	464	362
Liability for unpaid losses and LAE at end of year, gross	$ 161,079	$ 122,071	$ 96,613