Net Loss Per Share - Computation of Basic and Diluted Net Loss Per Share for Continuing and Discontinued Operations (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator:
Net loss, basic and diluted	$ (15,805)	$ (20,722)	$ (12,436)	$ (12,968)	$ (36,527)	$ (25,404)
Denominator:
Weighted average common shares outstanding	63,874		47,143		63,303	46,233
Weighted average unvested common shares subject to repurchase	(161)		(263)		(163)	(276)
Weighted average common shares outstanding—basic and diluted	63,713		46,880		63,140	45,957
Net loss per share, basic and diluted:	$ (0.25)		$ (0.27)		$ (0.58)	$ (0.55)