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The weighted average fair value per share of warrants issued and the 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) - Warrant [Member] - $ / shares
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Class of Warrant or Right [Line Items]      
Weighted average exercise price $ 5.63 $ 5.16 $ 6.83
Weighted average grant date fair value $ 3.00 $ 2.79 $ 3.67
Risk-free interest rate 2.52% 2.36% 1.47%
Volatility 60.80% 62.12% 63.24%
Term 5 years 5 years 5 years
Dividend yield 0.00% 0.00% 0.00%