Net Loss Per Share - Potentially Dilutive Securities Excluded from Diluted Net Loss Per Share (Detail) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities excluded from diluted net loss per share attributable to common stockholders, Total	5,406,712	2,204,050	5,406,712	2,204,050
Shares of common stock subject to outstanding options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities excluded from diluted net loss per share attributable to common stockholders, Total	1,842,110	1,515,154	1,842,110	1,515,154
Shares of common stock subject to outstanding common stock warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities excluded from diluted net loss per share attributable to common stockholders, Total	3,279,157	576,096	3,279,157	576,096
Restricted Stock Units (RSUs) [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities excluded from diluted net loss per share attributable to common stockholders, Total	285,445	112,800	285,445	112,800