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Stock-based Compensation - Summary of Valuation Assumptions Used (Details)
3 Months Ended
Mar. 31, 2020
Mar. 31, 2019
Weighted-average assumptions used in the Black-Scholes option pricing model to determine the fair value of the employee stock option grants    
Risk-free interest rate 1.50% 2.60%
Volatility 65.50% 63.30%
Expected term (in years) 6 years 1 month 6 days 6 years 1 month 6 days