Losses and Loss Adjustment Expenses - Liability for Unpaid Losses and Loss Adjustment Expenses (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Balance, beginning of year	$ 51,690	$ 48,908	$ 43,686
Incurred related to:
Current year	104,128	78,325	75,810
Prior years	20,539	8,899	3,658
Total incurred	124,667	87,224	79,468
Paid related to:
Current year	(64,812)	(51,095)	(47,650)
Prior years	(41,053)	(33,347)	(26,596)
Total paid	(105,865)	(84,442)	(74,246)
Balance, end of year	$ 70,492	$ 51,690	$ 48,908