Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (17,418)	$ (4,807)	$ (47,214)	$ (15,895)
Other comprehensive income (loss):
Unrealized gains (losses) related to short-term investments	(13)		38
Total other comprehensive loss	(13)		38
Comprehensive loss	$ (17,431)	$ (4,807)	$ (47,176)	$ (15,895)

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

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