v2.4.0.6
Exclusion of Potentially Dilutive Securities From Calculation of Diluted Net Loss Per Share (Detail)
3 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Dec. 31, 2012
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]      
Convertible notes 3,782,857 0  
Series A non-voting preferred stock 287,324 0 0
Shares underlying outstanding warrants 8,610,665 4,807,534  
Shares underlying outstanding stock options 3,298,297 1,547,122  
Total 15,979,143 6,354,656