Annual report pursuant to Section 13 and 15(d)

Stock-based Compensation - Option Valuation Method (Details)

v3.20.1
Stock-based Compensation - Option Valuation Method (Details)
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]    
Weighted average expected volatility, employees 66.47% 52.31%
Weighted average expected volatility, non-employees directors 65.36% 58.65%
Weighted average risk-free interest rate, employees 2.47% 2.64%
Weighted average risk-free interest rate, non-employees directors 2.11% 2.44%
Weighted average expected term (in years), employees 6 years 10 days 6 years 7 days
Weighted average expected term (in years), non-employees directors 5 years 6 months 14 days 5 years 3 months 10 days