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Equity - Assumptions used in Valuing the Stock Options Granted under Black-Scholes Valuation Model (Details) - Stock Option
3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Expected dividend yield 0.00% 0.00%
Expected volatility 75.00% 75.00%
Risk-free interest rate 2.52% 2.72%
Expected average life of options 7 years 6 years