Quarterly report pursuant to Section 13 or 15(d)

Capitalization and Equity Structure - Warrants (Details)

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Capitalization and Equity Structure - Warrants (Details) - $ / shares
 1 Months Ended 2 Months Ended 6 Months Ended
Jun. 30, 2020
Dec. 31, 2019
Feb. 28, 2021
Jun. 30, 2021
Jun. 30, 2020
May 31, 2019
Class Of Warrant Or Right, Outstanding [Roll Forward]            
Beginning balance (in shares)     1,325,000 1,325,000    
Warrants issued (in shares)       273,000    
Expired (in shares)       358,000 (223,000)  
Ending balance (in shares)       1,240,000    
2021 Warrants            
Schedule of Capitalization, Equity [Line Items]            
Exercise price (in dollars per share)     $ 12.81 $ 12.81    
Term (Years)     5 years 5 years    
Class Of Warrant Or Right, Outstanding [Roll Forward]            
Beginning balance (in shares)     0 0    
Warrants issued (in shares)     273,000 273,000    
Expired (in shares)       0    
Ending balance (in shares)       273,000    
June 2020 Investor Warrants            
Schedule of Capitalization, Equity [Line Items]            
Exercise price (in dollars per share) $ 5.18     $ 5.18 $ 5.18  
Term (Years)       5 years 6 months    
Class Of Warrant Or Right, Outstanding [Roll Forward]            
Beginning balance (in shares)     397,000 397,000    
Warrants issued (in shares)       0    
Expired (in shares)       270,000 0  
Ending balance (in shares) 874,000     127,000 874,000  
June 2020 Placement Agent Warrants            
Schedule of Capitalization, Equity [Line Items]            
Exercise price (in dollars per share)       $ 5.64    
Term (Years)       5 years    
Class Of Warrant Or Right, Outstanding [Roll Forward]            
Beginning balance (in shares)     122,000 122,000    
Warrants issued (in shares) 122,000     0    
Expired (in shares)       83,000 0  
Ending balance (in shares)       39,000    
December 2019 Warrants            
Schedule of Capitalization, Equity [Line Items]            
Exercise price (in dollars per share)   $ 8.10   $ 8.10    
Term (Years)   5 years   5 years    
Class Of Warrant Or Right, Outstanding [Roll Forward]            
Beginning balance (in shares)     556,000 556,000 556,000  
Warrants issued (in shares)       0    
Expired (in shares)       0    
Ending balance (in shares)   556,000   556,000    
December 2019 Placement Agent Warrants            
Schedule of Capitalization, Equity [Line Items]            
Exercise price (in dollars per share)   $ 8.44   $ 8.44    
Term (Years)       5 years    
Class Of Warrant Or Right, Outstanding [Roll Forward]            
Beginning balance (in shares)     52,000 52,000 52,000  
Warrants issued (in shares)       0    
Expired (in shares)       0    
Ending balance (in shares)   52,000   52,000    
May 2019 Warrants            
Schedule of Capitalization, Equity [Line Items]            
Exercise price (in dollars per share) $ 3.52     $ 3.52 $ 3.52 $ 3.52
Term (Years)       5 years    
Class Of Warrant Or Right, Outstanding [Roll Forward]            
Beginning balance (in shares)     198,000 198,000    
Warrants issued (in shares)       0    
Expired (in shares)       5,000 0  
Ending balance (in shares)       193,000