Net Loss Per Share - Computation of Company's Basic and Diluted Net Loss Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Net loss	$ (10,260)	$ (7,569)	$ (30,889)	$ (24,180)
Gain due to repurchase of Series A preferred stock				9
Net loss attributable to common stockholders	$ (10,260)	$ (7,569)	$ (30,889)	$ (24,171)
Weighted-average common shares used in computing net loss per share, basic and diluted	29,157,069	900,062	10,433,051	887,189
Net loss per share, basic and diluted	$ (0.35)	$ (8.41)	$ (2.96)	$ (27.25)