Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Assumptions (Details)

v3.20.4
Summary of Significant Accounting Policies - Assumptions (Details)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Weighted Average Fair Value of Stock Grants Using Black-Scholes Valuation Model [Abstract]      
Expected dividend yield 0.00% 0.00% 0.00%
Risk-free interest rate 0.50% 1.90% 2.60%
Expected volatility 87.30% 73.60% 50.20%
Expected life (in years) 3 years 3 months 18 days 3 years 3 months 18 days 3 years 3 months 18 days