Net Loss per Share of Common Stock - Summary of Potentially Dilutive Securities Excluded from Computation of Diluted Shares Outstanding (Detail)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Options to purchase common stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted shares outstanding	2,761,967	2,188,896
Restricted stock units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted shares outstanding	185,514