Net Loss per Common Share - Potential Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Common Share (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	2,770,909	3,084,076	2,770,909	3,084,076
Common Stock Options Outstanding [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	1,825,633	2,718,335	1,825,633	2,718,335
Unvested Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	945,276	365,741	945,276	365,741