Net Loss Per Common Share - Potential Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Common Share (Detail) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	1,342,221	2,536,891	1,342,221	2,536,891
Outstanding Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	385,974	1,012,833	385,974	1,012,833
Unvested Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	956,247	1,524,058	956,247	1,524,058