Net Loss per Share - Computation of Basic and Diluted Net Loss per Share Available to Common Stockholders (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Net loss	$ (9,530)	$ (4,787)	$ (5,684)	$ (4,689)	$ (4,172)	$ (6,545)	$ (3,645)	$ (3,383)	$ (24,690)	$ (17,745)	$ (3,963)
Add back: extinguishment of preferred shares											891
Net loss available to common stockholders - Basic and Diluted									$ (24,690)	$ (17,745)	$ (3,072)
Weighted-average common shares outstanding available to common stockholders
Basic and Diluted									24,620,372	20,965,935	4,133,138
Net loss per share available to common stockholders:
Basic and Diluted									$ (1.00)	$ (0.85)	$ (0.74)