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Fair Value Measurements (Schedule Of Financial Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($)
Sep. 30, 2020
Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Supplemental executive retirement plan assets $ 21,900,000 $ 26,000,000.0
Derivative Asset   5,400,000
Total Financial Assets 21,900,000 31,400,000
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Supplemental executive retirement plan assets   26,000,000.0
Derivative Asset   0
Total Financial Assets 21,900,000 26,000,000.0
Fair Value, Inputs, Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Supplemental executive retirement plan assets 0 0
Derivative Asset   5,400,000
Total Financial Assets 0 5,400,000
Significant Unobservable Inputs (Level 3) [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Supplemental executive retirement plan assets 0 0
Derivative Asset   0
Total Financial Assets $ 0 $ 0