Loss Per Share - Schedule of Basic and Diluted Net Loss Per Share (Detail) - 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
Earnings Per Share [Abstract]
Net loss	$ (27,840)	$ (32,393)	$ (31,806)	$ (23,634)	$ (25,683)	$ (21,940)	$ (92,039)	$ (71,257)
Weighted average shares outstanding, basic and diluted	58,754			48,554			54,218	46,547
Net loss per share, basic and diluted	$ (0.47)			$ (0.49)			$ (1.70)	$ (1.53)