Quarterly report pursuant to sections 13 or 15(d)

Summary of Significant Accounting Policies - Anti-Dilutive Securities Excluded from the Computation of Diluted Net Loss per Share (Detail)

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Summary of Significant Accounting Policies - Anti-Dilutive Securities Excluded from the Computation 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]    
Anti-dilutive securities excluded from the computation of diluted loss per share 2,755,283 786,956
Warrants for common stock [Member]
   
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Anti-dilutive securities excluded from the computation of diluted loss per share 1,848,487 28,210
Common stock options [Member]
   
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Anti-dilutive securities excluded from the computation of diluted loss per share 906,796 97,687
Redeemable convertible preferred stock [Member]
   
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Anti-dilutive securities excluded from the computation of diluted loss per share   661,059