Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (5,663)	$ (2,080)	$ (17,385)	$ (6,217)
Other comprehensive (loss) income, net of tax:
Foreign currency translation adjustments	(14)	(3)	(23)	42
Unrealized loss on marketable securities	(26)		(26)
Total other comprehensive (loss) income, net of tax	(40)	(3)	(49)	42
Comprehensive loss	$ (5,703)	$ (2,083)	$ (17,434)	$ (6,175)

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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