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						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator:
Net loss, basic and diluted	$ (15,669)	$ (15,805)	$ (20,722)	$ (14,567)	$ (12,436)	$ (12,968)	$ (52,196)	$ (39,971)
Denominator:
Weighted average common shares outstanding	64,884			56,010			63,845	49,528
Weighted average unvested common shares subject to repurchase	(123)			(274)			(176)	(276)
Weighted average common shares outstanding - basic and diluted	64,761			55,736			63,669	49,252
Net loss per share, basic and diluted:	$ (0.24)			$ (0.26)			$ (0.82)	$ (0.81)