Quarterly report pursuant to sections 13 or 15(d)

Stockholders' Equity - Reserved Shares of Authorized but Unissued Common Stock (Detail)

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Stockholders' Equity - Reserved Shares of Authorized but Unissued Common Stock (Detail)
Mar. 31, 2014
Dec. 31, 2013
Class of Stock [Line Items]    
Total reserved shares of common stock 2,898,534 2,320,021
Outstanding common stock warrants [Member]
   
Class of Stock [Line Items]    
Total reserved shares of common stock 1,848,487 1,742,727
Equity incentive plans [Member]
   
Class of Stock [Line Items]    
Total reserved shares of common stock 1,050,047 577,294