Net Loss Per Share - Basic and Diluted Loss Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share [Abstract]
Net loss	$ (8,805)	$ (12,007)	$ (12,269)	$ (28,223)
Weighted average common shares outstanding, basic and diluted (in shares)	59,715	57,844	59,430	57,635
Net loss per share, basic and diluted (USD per share)	$ (0.15)	$ (0.21)	$ (0.21)	$ (0.49)