Quarterly report pursuant to Section 13 or 15(d)

Stock-Based Compensation - Fair Value of Options Estimated on Date of Grant Using Black-Scholes Option Pricing Model (Details)

v3.19.3
Stock-Based Compensation - Fair Value of Options Estimated on Date of Grant Using Black-Scholes Option Pricing Model (Details)
9 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Minimum    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Range of expected option life 5 years 6 months 5 years 6 months
Expected volatility 74.69% 74.05%
Risk-free interest rate 1.42% 2.32%
Maximum    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Range of expected option life 6 years 6 years
Expected volatility 80.59% 81.47%
Risk-free interest rate 2.66% 2.98%