Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net loss	$ (28,578)	$ (13,844)	$ (14,193)
Other comprehensive income (loss):
Unrealized income (loss) on marketable securities, net of tax	48	(27)	0
Gains on marketable securities reclassified into earnings, net of tax	(27)	0	0
Total	21	(27)	0
Unrealized income (loss) on short-term investments, net of tax	(7,531)	3,291	184
Losses (gains) on derivative instruments reclassified into earnings, net of tax	3,741	(2,649)	(332)
Total	(3,790)	642	(148)
Total other comprehensive income (loss)	(3,769)	615	(148)
Comprehensive loss	$ (32,347)	$ (13,229)	$ (14,341)