Financial Instruments - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value Of Financial Instruments [Line Items]
Fair value of note payable	$ 5,300	$ 5,300
Cash and cash equivalents	29,902	45,824	$ 34,194	$ 18,162
Cash held outside United States, principally in Netherlands, United Kingdom, China, and Canada	19,700	25,600
Credit Facility [Member]
Fair Value Of Financial Instruments [Line Items]
Fair value of debt issued	$ 114,900	$ 125,100