CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (17,562)	$ (13,282)	$ (36,354)	$ (27,167)
Other comprehensive income (loss)
Unrealized gains (losses) on available-for-sale investments, net of taxes	161	9	372	(320)
Comprehensive loss	$ (17,401)	$ (13,273)	$ (35,982)	$ (27,487)

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

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