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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	2,236,895	2,776,490	2,236,895	2,776,490
Outstanding Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	849,953	1,303,007	849,953	1,303,007
Unvested Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	1,386,942	1,473,483	1,386,942	1,473,483