Goodwill and Intangible Assets - Change in the Carrying Value of Goodwill (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Balance, Beginning Balance	$ 61,044	$ 61,074
Adjustments	323	(30)	[1]
Goodwill from distributor acquisitions	3,247
Balance, Ending Balance	$ 64,614	$ 61,044

[1] The adjustments to goodwill during the period were related to foreign currency translation and/or purchase accounting adjustments within the measurement period.