Summary of Significant Accounting Policies - Schedule of Potentially Dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total	2,438,653	11,090,513	2,438,653	11,090,513
Convertible Notes [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total		3,304,252		3,304,252
Common Stock Options [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total	2,373,996	1,324,297	2,373,996	1,324,297
Warrants to Purchase Preferred Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total	64,657	901,987	64,657	901,987
Convertible Preferred Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total		5,559,977		5,559,977