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The ranges of assumptions used in the Black-Scholes Model during the years ended December 31, 2019, 2018, and 2017 are set forth in the table below. (Details) - Share-based Payment Arrangement, Option [Member] - $ / shares
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Weighted average exercise price $ 3.10 $ 5.45 $ 6.60
Weighted average grant date fair value $ 1.82 $ 3.24 $ 3.82
Risk-free interest rate - minimum 1.64% 2.38% 1.84%
Risk-free interest rate - maximum 2.54% 2.89% 2.05%
Volatility - minimum 61.25% 59.45% 61.56%
Volatility - maximum 64.49% 64.04% 64.25%
Dividend yield 0.00% 0.00% 0.00%
Minimum [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Term 5 years 6 months 5 years 1 month 6 days 5 years 6 months
Maximum [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Term 6 years 6 months 6 years 3 months 6 years 3 months