Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity - Additional Information (Detail)

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Stockholders' Equity - Additional Information (Detail) (USD $)
 0 Months Ended 9 Months Ended
Jul. 25, 2014
Nov. 22, 2013
Oct. 31, 2013
Sep. 30, 2013
Sep. 30, 2013
Sep. 30, 2014
Jul. 25, 2014
Dec. 31, 2013
Nov. 22, 2013
Oct. 31, 2013
Class of Stock [Line Items]                    
Issuance of common stock upon conversion of redeemable convertible preferred stock       2,793,281            
Conversion of preferred stock to common stock       $ 320,000,000 $ 323,155,000          
Convertible preferred stock issued           0   0    
Convertible preferred stock outstanding           0   0    
Common stock, shares authorized           100,000,000   100,000,000    
Common stock, par value           $ 0.0001   $ 0.0001    
Common stock shares sold       5,366,669 5,366,669 14,684,788   9,455,064 604,000 664,300
Warrants to purchase shares of common stock in 2013 financing       1,073,338 1,073,338       120,800 132,860
Net proceeds from issuance of 2013 financing     2,200,000 22,800,000            
Loan facility extinguished in exchange of common stock       624,944            
Amount of debt cancelled upon issuance of common stock shares       16,900,000            
Net proceeds from issuance of 2013 financing   2,700,000   26,800,000            
Shares issued in public offering 4,600,000                  
Common stock offering price             $ 5.50      
Net proceeds from public offering $ 23,000,000                  
Series B-1 Preferred [Member]
                    
Class of Stock [Line Items]                    
Common stock, shares authorized           100,000,000        
Common stock, par value           $ 0.0001