Net Loss Per Share - Potentially Dilutive Securities Excluded from Calculation of Net Loss per Share (Detail)	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	78,770,335	65,184,376
Common Shares Issuable Upon Conversion of all Series Preferred [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	75,402,332	61,796,890
Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	2,856,905	2,876,388
Warrant [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	511,098	511,098