Quarterly report pursuant to Section 13 or 15(d)

Organization and Description of Business - Additional Information (Detail)

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Organization and Description of Business - Additional Information (Detail) (USD $)
 0 Months Ended 3 Months Ended 9 Months Ended
Jul. 25, 2014
Nov. 22, 2013
Oct. 31, 2013
Sep. 30, 2013
Sep. 30, 2014
Sep. 30, 2013
Sep. 30, 2014
Sep. 30, 2013
Jul. 25, 2014
Dec. 31, 2013
Jun. 20, 2006
Organization, Consolidation and Presentation of Financial Statements [Abstract]                      
Shares issued in public offering 4,600,000                    
Common stock offering price                 $ 5.50    
Net proceeds from public offering $ 23,000,000                    
Gross proceeds from issuance of common stock and warrants in a private placement   2,700,000   26,800,000              
Additional proceeds from venture debt financing       5,000,000              
Venture debt financing loan agreement amount           10,000,000   10,000,000     30,000,000
Net proceeds after deducting placement agent fees and estimated offering expenses       28,800,000              
Net proceeds from issuance of private placement     2,200,000 22,800,000              
Issued shares of common stock in cancellation of debt       16,900,000              
Net losses         (5,961,000) (1,307,000) (19,195,000) (6,159,000)      
Cash flows from operating activities             (13,642,000)        
Accumulated deficit         $ (368,037,000)   $ (368,037,000)     $ (348,842,000)