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3. Accounting for Stock-based Compensation - Valuation Assumptions (Details) - $ / shares
3 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Share-based Payment Arrangement [Abstract]    
Weighted average grant date fair value $ 13.88
Weighted average assumptions used:    
Expected dividend yield 0.00%
Risk-free interest rate 0.67%
Expected volatility 73.00%
Expected life (in years) (Year) 5 years