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Stock Plans - Black-Scholes Assumptions (Details) - Stock options - $ / shares
12 Months Ended
Dec. 31, 2022
Dec. 31, 2021
Dec. 31, 2020
Weighted-average assumptions      
Expected stock price volatility 74.10% 82.30% 74.50%
Risk-free interest rate 3.10% 0.70% 1.00%
Expected life of options (in years) 4 years 1 month 24 days 4 years 2 months 23 days 4 years 5 months 19 days
Expected dividend yield 0.00% 0.00% 0.00%
Weighted-average fair value (PSV) of the options (in dollars per share) $ 0.71 $ 1.83 $ 2.79