Premiums Receivable - Summarizes the Activity in the Allowance for Doubtful Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Premiums Receivable, Allowance for Doubtful Accounts [Roll Forward]
Balance, beginning of year	$ 4,852	$ 5,211	$ 5,458
Provision for bad debts	1,646	806	673
Write-offs	(1,286)	(1,165)	(920)
Balance, end of year	$ 5,212	$ 4,852	$ 5,211