Summary of Significant Accounting Policies (Potential Common Stock Equivalents Excluded from Calculation of Diluted Net Loss per Share) (Detail)	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common stock equivalents excluded from the calculation of diluted net loss per share	42,079,800	38,872,275
Stock Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common stock equivalents excluded from the calculation of diluted net loss per share	4,810,675	1,603,150
Warrant [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common stock equivalents excluded from the calculation of diluted net loss per share	37,269,125	37,269,125