Net Loss Per Share Available to Common Stockholders - Calculation of Basic and Diluted Net Loss Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Numerator:
Net loss available to common stockholders	$ (16,480)	$ (33,349)	$ (33,171)
Denominator:
Weighted average number of shares, basic and diluted	38,318	36,580	34,210
Net loss per share available to common stockholders:
Basic and diluted net loss per common share available to common stockholders	$ (0.43)	$ (0.91)	$ (0.97)