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Fair Value Measurements - Estimated Fair Value of Warrant Liability (Details)
1 Months Ended 3 Months Ended 6 Months Ended
Jan. 08, 2021
shares
Jul. 21, 2020
USD ($)
shares
Jan. 31, 2021
USD ($)
shares
May 31, 2020
$ / shares
shares
Jun. 30, 2021
USD ($)
$ / shares
shares
Jun. 30, 2021
USD ($)
$ / shares
shares
Dec. 31, 2020
USD ($)
$ / shares
Apr. 30, 2020
$ / shares
Jul. 23, 2019
$ / shares
Series A Warrants                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Change in fair value         $ 0 $ 0      
Series A Warrants | Stock price                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Warrant liability | $ / shares         1.58 1.58 0.82    
Series A Warrants | Strike price                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Warrant liability | $ / shares         787.50 787.50 787.50    
Series A Warrants | Expected life                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Weighted-average expected term (years)         10 months 28 days 10 months 28 days 1 year 4 months 28 days    
Series A Warrants | Volatility                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Warrant liability         199 199 148    
Series A Warrants | Risk free rate                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Warrant liability         0.07 0.07 0.13    
Series 3 warrants                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Weighted-average expected term (years)       5 years          
Number of warrants purchase common stock exchanged | shares 406,250     4,005,062          
Warrants exercised | shares   8,456,352     620,750 620,750      
Warrants conversion | shares       1          
Aggregate fair value of the common stocks issued by the exercise of Warrants   $ 6,100,000       $ 1,800,000      
Series 3 warrants | Stock price                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Warrant liability | $ / shares       0.05     0.82    
Series 3 warrants | Strike price                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Warrant liability | $ / shares       0.44     0.00    
Series 3 warrants | Expected life                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Weighted-average expected term (years)       5 years 6 months     4 years 10 months 20 days    
Series 3 warrants | Volatility                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Warrant liability       141     142    
Series 3 warrants | Risk free rate                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Warrant liability       0.34     0.36    
Underwriter Warrants                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Fair value of warrant         $ 7,000 $ 7,000      
Underwriter Warrants | Stock price                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Warrant liability | $ / shares         1.58 1.58 0.82 2.50  
Underwriter Warrants | Strike price                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Warrant liability | $ / shares         52.50 52.50 52.50 0.45  
Underwriter Warrants | Expected life                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Weighted-average expected term (years)         2 years 3 months 3 days 2 years 3 months 3 days 2 years 9 months 3 days 4 years 3 months  
Underwriter Warrants | Volatility                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Warrant liability         157 157 156 141  
Underwriter Warrants | Risk free rate                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Warrant liability         0.25 0.25 0.17 0.29  
2019 Bridge Note Warrants                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Warrants exercised | shares 406,250                
2019 Bridge Note Warrants | Strike price                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Warrant liability | $ / shares                 2.00
2019 Bridge Note Warrants | Expected life                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Weighted-average expected term (years)                 4 years 9 months 18 days
2019 Bridge Note Warrants | Volatility                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Warrant liability                 145.84
2019 Bridge Note Warrants | Risk free rate                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Warrant liability                 1.76
Warrant liability | Recurring | Level 3                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Fair value of warrant         $ 7,000 $ 7,000 $ 179,000    
Change in fair value           141,000      
Warrant liability | Series A Warrants                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Fair value of warrant         0 0 $ 0    
Warrant liability             0    
Warrant liability | Series 3 warrants                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Fair value of warrant             $ 175,000    
Change in fair value         $ 0 $ 138,000      
Number of warrants purchase common stock exchanged | shares     406,250            
Warrants exercised | shares         620,750 620,750      
Warrants conversion | shares           1      
Aggregate fair value of the common stocks issued by the exercise of Warrants     $ 1,500,000     $ 1,800,000      
Warrant liability | Underwriter Warrants                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Fair value of warrant         $ 7,000 7,000 $ 4,000    
Change in fair value         $ 5,000 $ 3,000      
Warrant liability | 2019 Bridge Note Warrants                  
Fair Value Assumptions and Methodology for Assets and Liabilities                  
Warrants exercised | shares     406,250