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Stockholders' Equity - Summary of Fair Value of Option Grant on Grant Date Using Black-Scholes Option Pricing Model (Details) - Share-based Payment Arrangement, Option
9 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Risk-free interest rate 2.10% 2.80%
Dividend yield 0.00% 0.00%
Volatility 67.40% 70.50%
Expected life 6 years 6 years