Net Loss Per Share - Computation of 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	$ (4,787)	$ (6,545)	$ (15,160)	$ (13,573)
Weighted-average common shares outstanding:
Basic and Diluted	25,545,164	22,713,040	23,737,443	20,351,005
Net loss per share, Basic and Diluted	$ (0.19)	$ (0.29)	$ (0.64)	$ (0.67)