Potentially Dilutive Securities Not Included in Calculation of Diluted Net Loss per Share (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities not included in calculation of diluted net loss per share	1,949,096	3,041,033	3,762,394	3,875,462
Common Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities not included in calculation of diluted net loss per share	1,949,096	3,041,033	2,313,182	2,474,614
Convertible Note Payable
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities not included in calculation of diluted net loss per share			1,449,212	1,400,848