Quarterly report pursuant to Section 13 or 15(d)

Capital Stock - Biotechnology Value Fund Financing - Additional Information (Details)

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Capital Stock - Biotechnology Value Fund Financing - Additional Information (Details) - USD ($)
$ / shares in Units, $ in Millions
 1 Months Ended 3 Months Ended
Feb. 28, 2017
Mar. 31, 2018
Dec. 31, 2017
Class Of Warrant Or Right [Line Items]      
Cash proceeds from issuance of common stock and convertible preferred stock $ 24.8    
Preferred stock, stated value   $ 0.05 $ 0.05
Ownership percentage on outstanding shares   18.00%  
Convertible Preferred Stock (as Converted) [Member]      
Class Of Warrant Or Right [Line Items]      
Sale of shares 5,003    
Preferred stock, stated value $ 4,030    
Conversion of preferred stock into registered common stock 1,000    
Preferred stock conversion price per share $ 4.03    
Total number of shares of common stock issued upon conversion 5,003,000    
Percentage of convertible preferred stock conversion blocker provision 19.99%    
Convertible preferred stock voting rights description   Shares of Series X convertible preferred stock will generally have no voting rights, except as required by law and except that the consent of the holders of the outstanding Series X convertible preferred stock will be required to amend the terms of the Series X preferred stock and to approve certain corporate actions.  
Ownership percentage on outstanding shares upon conversion   48.80%  
Preferred shares converted   0  
Fair value of common stock amount exceeded purchase price of convertible preferred stock $ 5.6    
Common Stock [Member]      
Class Of Warrant Or Right [Line Items]      
Sale of shares 1,200,000    
Common stock share price $ 4.03