Consolidated Statements of Comprehensive Loss - 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	$ (14,987)	$ (18,663)	$ (43,444)	$ (52,336)
Other comprehensive loss:
Foreign currency translation adjustment	(947)	(127)	(997)	(548)
Changes in unrealized gain (loss) on investments, net of income taxes of $(12) thousand and $257 thousand for the three and nine months ended September 30, 2019, respectively, and $0 for the three and nine months ended September 30, 2018.	(203)	72	811	(164)
Comprehensive loss	$ (16,137)	$ (18,718)	$ (43,630)	$ (53,048)