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Stock-Based Compensation - Schedule of Assumptions Used to Determine Fair Value of Options Granted (Details)
6 Months Ended
Jun. 30, 2019
Jun. 30, 2018
Risk-free interest rate, minimum 2.42% 308.50%
Risk-free interest rate, maximum 2.65%  
Expected volatility, minimum 101.30% 99.90%
Expected volatility, maximum 106.20% 100.00%
Expected dividend yield 0.00% 0.00%
Minimum [Member]    
Expected life (in years) 7 years 6 months 9 years 6 months
Maximum [Member]    
Expected life (in years) 9 years 3 months 19 days 10 years