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Fair Value (Carrying Amount And Estimated Fair Values Of Financial Instruments) (Details) - USD ($)
$ in Millions
Dec. 31, 2020
Dec. 31, 2019
Fair Value Disclosures [Abstract]    
Long-term debt (including current portion), Carrying Amount $ 9,243.1 $ 7,869.6
Long-term debt (including current portion), Estimated Fair Value $ 11,034.2 $ 8,764.4