Annual report pursuant to Section 13 and 15(d)

Capitalization and Equity Structure - 2017 Offerings (Details)

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Capitalization and Equity Structure - 2017 Offerings (Details)
$ / shares in Units, shares in Thousands, $ in Thousands
 1 Months Ended 12 Months Ended
Aug. 31, 2017
USD ($)
$ / shares
shares
Apr. 30, 2017
USD ($)
$ / shares
shares
Dec. 31, 2018
USD ($)
$ / shares
shares
Dec. 31, 2017
USD ($)
$ / shares
shares
Sep. 30, 2017
$ / shares
shares
Dec. 31, 2015
$ / shares
shares
Jan. 15, 2014
$ / shares
shares
Class of Warrant or Right [Line Items]              
Class Of Warrant Or Right Issued | shares     0        
Common Stock, par value (in dollars per share) | $ / shares     $ 0.001 $ 0.001      
Number warrants called (in shares) | shares           2,122 89
Proceeds from issuance of common stock, net | $     $ 4,446 $ 42,463      
April 2017 equity financing, net of underwriting discount & issuance costs of $662 | $ $ 34,000   $ 4,446 $ 11,058      
Shares issued (in dollars per share) | $ / shares $ 1.00            
Shares subscription 1.1608            
Issuance of warrants | $ $ 131            
Common Stock              
Class of Warrant or Right [Line Items]              
Issuance of common stock, net of underwriting discount & issuance costs (in shares) | shares   3,732 2,032 3,732      
Common Stock, par value (in dollars per share) | $ / shares   $ 0.001          
Number warrants called (in shares) | shares   1,866 88        
Proceeds from issuance of common stock, net | $   $ 10,919          
April 2017 equity financing, net of underwriting discount & issuance costs of $662 | $     $ 2 $ 4      
Exercise price (in dollars per share) | $ / shares     $ 9.66        
Warrants for common stock              
Class of Warrant or Right [Line Items]              
Number warrants called (in shares) | shares             5,151
Payment of issuance costs | $   $ 185          
Exercise price (in dollars per share) | $ / shares             $ 7.00
Maximum              
Class of Warrant or Right [Line Items]              
Percentage of common stock outstanding 40.00%            
Minimum | Warrants for common stock              
Class of Warrant or Right [Line Items]              
Exercise price (in dollars per share) | $ / shares           $ 3.74  
Puissance Cross-Border Opportunities II LLC              
Class of Warrant or Right [Line Items]              
Issuance of common stock, net of underwriting discount & issuance costs (in shares) | shares 20,535            
Warrant Repurchase Agreement              
Class of Warrant or Right [Line Items]              
Repurchase of shares (in dollars per share) | $ / shares $ 1.23 $ 1.23          
Number of warrants repurchased (in shares) | shares 1,866            
Payments for repurchase of warrants | $ $ 2,245            
Rights Offering              
Class of Warrant or Right [Line Items]              
Issuance of common stock, net of underwriting discount & issuance costs (in shares) | shares 13,465            
Proceeds from issuance of common stock, net | $ $ 13,179            
April 2017 equity financing, net of underwriting discount & issuance costs of $662 | $ 13,465            
Payment of issuance costs | $ 286            
Backstop Investor Offering              
Class of Warrant or Right [Line Items]              
April 2017 equity financing, net of underwriting discount & issuance costs of $662 | $ $ 20,535            
Information Agent Warrants              
Class of Warrant or Right [Line Items]              
Class Of Warrant Or Right Issued | shares     0        
Number warrants called (in shares) | shares         200    
Exercise price (in dollars per share) | $ / shares     $ 1.5   $ 1.50    
Term (Years)     3 years        
2017 Warrants              
Class of Warrant or Right [Line Items]              
Class Of Warrant Or Right Issued | shares   1,866          
Exercise price (in dollars per share) | $ / shares   $ 4.10          
Term (Years)   5 years