Summary of Significant Accounting Policies (Potential Common Stock Equivalents Excluded from Calculation of Diluted Net Loss per Share) (Detail)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 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	43,260,925	46,233,041
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	5,991,800	2,435,500
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	2,187,158
Convertible Preferred Stock [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	0	39,089,161
Convertible Debt [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	0	2,521,222