Annual report pursuant to Section 13 and 15(d)

Capitalization and Equity Structure - Warrant Share Activity (Details)

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Capitalization and Equity Structure - Warrant Share Activity (Details) - $ / shares
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Sep. 30, 2017
Class Of Warrant Or Right, Outstanding [Roll Forward]        
Merger/PPO Warrant Shares Outstanding (in shares) 3,396,000      
Merger/PPO Warrant Shares Issued (in shares) 0      
Merger/PPO Warrant Shares Expired (in shares) 0      
Merger/PPO Warrant Shares Exercised (in shares) 0      
Merger/PPO Warrant Shares Outstanding (in shares) 3,396,000 3,396,000    
Information Agent Warrants        
Schedule of Capitalization, Equity [Line Items]        
Exercise price (in dollars per share) $ 1.5     $ 1.50
Term (Years) 3 years      
Class Of Warrant Or Right, Outstanding [Roll Forward]        
Merger/PPO Warrant Shares Outstanding (in shares) 200,000      
Merger/PPO Warrant Shares Issued (in shares) 0      
Merger/PPO Warrant Shares Expired (in shares) 0      
Merger/PPO Warrant Shares Exercised (in shares) 0      
Merger/PPO Warrant Shares Outstanding (in shares) 200,000 200,000    
2015 Warrants        
Schedule of Capitalization, Equity [Line Items]        
Exercise price (in dollars per share) $ 3.74      
Term (Years) 5 years      
Class Of Warrant Or Right, Outstanding [Roll Forward]        
Merger/PPO Warrant Shares Outstanding (in shares) 1,604,000      
Merger/PPO Warrant Shares Issued (in shares) 0      
Merger/PPO Warrant Shares Expired (in shares) 0      
Merger/PPO Warrant Shares Exercised (in shares) 0 30,000 488,000  
Merger/PPO Warrant Shares Outstanding (in shares) 1,604,000 1,604,000    
Placement agent warrants        
Schedule of Capitalization, Equity [Line Items]        
Exercise price (in dollars per share) $ 7      
Term (Years) 5 years      
Class Of Warrant Or Right, Outstanding [Roll Forward]        
Merger/PPO Warrant Shares Outstanding (in shares) 426,000      
Merger/PPO Warrant Shares Issued (in shares) 0      
Merger/PPO Warrant Shares Expired (in shares) 0      
Merger/PPO Warrant Shares Exercised (in shares) 0      
Merger/PPO Warrant Shares Outstanding (in shares) 426,000 426,000    
PPO warrants        
Schedule of Capitalization, Equity [Line Items]        
Exercise price (in dollars per share) $ 14      
Term (Years) 5 years      
Class Of Warrant Or Right, Outstanding [Roll Forward]        
Merger/PPO Warrant Shares Outstanding (in shares) 1,078,000      
Merger/PPO Warrant Shares Issued (in shares) 0      
Merger/PPO Warrant Shares Expired (in shares) 0      
Merger/PPO Warrant Shares Exercised (in shares) 0      
Merger/PPO Warrant Shares Outstanding (in shares) 1,078,000 1,078,000    
Pre 2014 warrants        
Schedule of Capitalization, Equity [Line Items]        
Exercise price (in dollars per share) $ 9.66      
Class Of Warrant Or Right, Outstanding [Roll Forward]        
Merger/PPO Warrant Shares Outstanding (in shares) 88,000      
Merger/PPO Warrant Shares Issued (in shares) 0      
Merger/PPO Warrant Shares Expired (in shares) 0      
Merger/PPO Warrant Shares Exercised (in shares) 0      
Merger/PPO Warrant Shares Outstanding (in shares) 88,000 88,000    
Pre 2014 warrants | Minimum        
Schedule of Capitalization, Equity [Line Items]        
Term (Years) 9 years      
Pre 2014 warrants | Maximum        
Schedule of Capitalization, Equity [Line Items]        
Term (Years) 10 years