Income Taxes - Summary of Changes in Deferred Tax Valuation Allowance (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Deferred tax valuation allowance, Beginning Balance	$ 2,193	$ 1,534	$ 1,565
Additions	1,439	1,256	150
Deductions	(70)	(455)	(134)
Change in tax legislation	(954)
Translation adjustments	78	(142)	(47)
Deferred tax valuation allowance, Ending Balance	$ 2,686	$ 2,193	$ 1,534