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Stock Options And Restricted Stock Awards (Weighted-Average Estimated Fair Value of Employee Stock Options Granted) (Details) - Stock Options [Member] - $ / shares
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Weighted average fair value $ 29.78 $ 14.72
Risk-free discount rate, minimum 1.72% 2.32%
Risk-free discount rate, maximum 2.29% 2.84%
Volatility 43.00% 45.00%
Minimum [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected life 4 years 2 months 12 days 4 years 1 month 6 days
Maximum [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Expected life 4 years 4 months 24 days 4 years 2 months 12 days