CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Comprehensive Income (loss)
Net loss	$ (51,675)	$ (65,772)	$ (82,751)
Other comprehensive loss:
Gain (loss) on short-term investments	6	(5)	2
Reclassification of gains included in net loss			(3)
Total other comprehensive income (loss)	6	(5)	(1)
Comprehensive loss	$ (51,669)	$ (65,777)	$ (82,752)