Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (11,100)	$ (15,448)
Other comprehensive loss:
Foreign currency translation adjustment	(304)	298
Changes in unrealized gain (loss) on investments, net of income taxes of $113 thousand for the three months ended March 31, 2019 and $0 for the three months ended March 31, 2018, respectively	426	(379)
Comprehensive loss	$ (10,978)	$ (15,529)