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Stock Plans and Stock-Based Compensation - Key Assumptions (Details) - Employees and Officers
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]      
Expected term (years) 5 years 6 months 5 years 6 months 5 years 6 months
Minimum risk-free interest rate (percent) 0.40% 0.40% 1.50%
Maximum risk-free interest rate (percent) 1.40% 1.70% 2.60%
Minimum volatility (percent) 107.00% 80.00% 76.00%
Maximum volatility (percent) 111.00% 81.00% 79.00%
Dividends (percent) 0.00% 0.00% 0.00%