Schedule II - Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance, beginning of year	$ 1,719	$ 2,239	$ 2,703
Provision	49	32	7
Write-offs, recoveries and discounts allowed	(29)	(497)	(275)
Other	218	(55)	(196)
Balance, end of year	1,957	1,719	2,239
Allowance for Sales Discounts and Deductions [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance, beginning of year	1,462	1,593	1,809
Provision	4,610	4,283	3,856
Write-offs, recoveries and discounts allowed	(4,697)	(4,368)	(3,649)
Other	68	(46)	(423)
Balance, end of year	$ 1,443	$ 1,462	$ 1,593