Potential Common Stock Equivalents Excluded from Calculation of Diluted Net Loss per Share (Detail)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
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	46,233,041	34,735,285
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	2,435,500	2,135,667
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	2,187,158	2,150,000
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	39,089,161	28,160,200
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	2,521,222	2,289,418