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Stock-Based And Long-Term Incentive Compensation (Summary Of The Valuation Assumptions Used To Calculate The Fair Value Of Stock Option Grants) (Details) - $ / shares
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]      
Weighted average fair value of stock options granted $ 24.60 $ 56.12 $ 83.60
Black-Scholes-Merton Assumptions:      
Risk free interest rate 2.57% 2.43% 1.96%
Expected life (years) 6 years 6 years 6 years
Volatility 56.62% 51.21% 48.22%