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				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share [Abstract]
Net loss	$ (25,683)	$ (21,940)	$ (22,219)	$ (21,356)	$ (47,623)	$ (43,575)
Weighted average shares outstanding, basic and diluted	45,814		42,836		45,526	42,441
Net loss per share, basic and diluted	$ (0.56)		$ (0.52)		$ (1.05)	$ (1.03)