Net Loss Per Share Attributable to Common Stockholders - Schedule of Antidilutive Common Stock Equivalents Excluded from Calculation of 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 Common Stock Equivalents excluded from Calculation of Diluted Net Loss Per Share	15,718,758	7,857,948	15,718,758	7,857,948
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Common Stock Equivalents excluded from Calculation of Diluted Net Loss Per Share	4,622,600	3,640,000	4,622,600	3,640,000
Warrants to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Common Stock Equivalents excluded from Calculation of Diluted Net Loss Per Share	352,415	264,000	352,415	264,000
Series A and Series B Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Common Stock Equivalents excluded from Calculation of Diluted Net Loss Per Share	10,689,027	3,899,232	10,689,027	3,899,232
Warrants to Purchase Preference Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Common Stock Equivalents excluded from Calculation of Diluted Net Loss Per Share	54,716	54,716	54,716	54,716