Net Loss per Share - Outstanding Options, Warrants and Preferred Stock Excluded from Computation of Diluted Net Loss per Share (Detail) - shares	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Convertible preferred stock (as converted)
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share		2,353,163
Options to purchase common stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	610,090	553,622
Warrant | Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	170,587	931
Warrant | Convertible preferred stock (as converted)
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share		27,534