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Stockholders' Equity Stockholders' Equity (Status of stock based compensation plans) (Details) - shares
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Options Outstanding (in shares) 912,000 1,078,000 1,523,000 1,934,000
2017 Plan [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant 1,782,824