Net Loss per Share of Common Stock - Summary of Potentially Dilutive Securities Excluded from Computation of Diluted Shares Outstanding (Detail)	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Convertible preferred stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted shares outstanding		8,945,252
Warrants to purchase convertible preferred stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted shares outstanding		173,910
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	2,477,446	828,382
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	104,821