Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (4,538)	$ (6,803)	$ (6,669)	$ (11,755)
Other comprehensive loss:
Effect of foreign currency translation		(7)		(26)
Comprehensive net loss	$ (4,538)	$ (6,810)	$ (6,669)	$ (11,781)

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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