Net loss per share - Schedule of Antidilutive Securities Excluded from Computation of Basic and Diluted Net Loss Per Share (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from the computation of basic and diluted net loss per share	817,022	6,039,706	817,022	6,039,706
Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from the computation of basic and diluted net loss per share		5,525,844		5,525,844
Outstanding Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from the computation of basic and diluted net loss per share	805,659	513,862	805,659	513,862
Common Stock Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from the computation of basic and diluted net loss per share	11,363		11,363