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Stockholders' Equity Stockholders' Equity (Four quarterly assumptions for fair value of the right (option) to purchase shares under ESPP) (Details) - Employee Stock Purchase Plan
3 Months Ended 12 Months Ended
Dec. 31, 2021
Sep. 30, 2021
Jun. 30, 2021
Mar. 31, 2021
Dec. 31, 2020
Sep. 30, 2020
Jun. 30, 2020
Mar. 31, 2020
Dec. 31, 2019
Sep. 30, 2019
Jun. 30, 2019
Mar. 31, 2019
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                              
Dividend yield                         0.01% 1.50% 1.40%
Expected volatility                         48.10% 48.60% 36.10%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate 10.00% 10.00% 9.00% 9.00% 156.00% 157.00% 157.00% 154.00% 260.00% 256.00% 251.00% 242.00%      
Expected life (years) 1 year 9 months 6 months 3 months 1 year 9 months 6 months 3 months 1 year 9 months 6 months 3 months