Condensed Consolidated Statements of Loss and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net loss	$ (22,929)	$ (15,871)	$ (63,328)	$ (47,371)
Other comprehensive income (loss);
Unrealized gain (loss) on fair value of investments	(99)	(41)	101	48
Unrealized loss on currency translation		(2)		(1)
Comprehensive loss	$ (23,028)	$ (15,914)	$ (63,227)	$ (47,324)