CONDENSED 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 Comprehensive Income [Abstract]
Net loss	$ (40,853)	$ (37,989)	$ (77,673)	$ (70,477)
Other comprehensive income (loss):
Change in unrealized gain (loss) on investments, net of tax	7	(2)	130	40
Other comprehensive income (loss)	7	(2)	130	40
Comprehensive loss	$ (40,846)	$ (37,991)	$ (77,543)	$ (70,437)