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Stock-Based Compensation - Option Pricing Assumptions (Details)
3 Months Ended
Mar. 31, 2020
Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected dividend yield 0.00% 0.00%
Expected term 6 years 3 months 6 years 3 months
Minimum    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected volatility 67.30% 73.70%
Risk-free interest rate 0.60% 2.30%
Maximum    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected volatility 69.50% 74.40%
Risk-free interest rate 1.80% 2.60%