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Stock-Based Compensation (Schedule of Fair Value of the Stock Options Granted) (Details) - Stock Options [Member] - $ / shares
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]    
Expected dividend yield over expected term 0.00% 0.00%
Resulting weighted average grant date fair value $ 3.47 $ 14.20
Minimum [Member]    
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]    
Expected term (years) 5 years 5 years
Risk free interest rate 0.41% 2.105%
Volatility 96.00% 103.00%
Maximum [Member]    
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]    
Expected term (years) 6 years 6 years
Risk free interest rate 0.57% 2.61%
Volatility 115.00% 110.00%