Net Loss per Share - Summary of Reconciliation of Denominator Used in Calculation 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, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Earnings Per Share Basic And Diluted [Abstract]
Net loss	$ (11,064)	$ (11,392)	$ (21,218)	$ (22,250)
Weighted-average common shares outstanding — basic	35,023	33,208	34,858	32,432
Weighted-average common shares, outstanding — diluted	35,023	33,208	34,858	32,432
Net loss per share, basic and diluted	$ (0.32)	$ (0.34)	$ (0.61)	$ (0.69)