XML 45 R35.htm IDEA: XBRL DOCUMENT v3.21.1
Share-Based Compensation - Weighted-average Assumptions (Details) - Options to purchase common stock - $ / shares
3 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected stock price volatility 66.70% 75.20%
Risk free interest rate 0.40% 1.70%
Expected life of options (years) 5 years 4 months 24 days 5 years 8 months 1 day
Expected annual dividend per share (in dollars per share) $ 0 $ 0