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Financial Instruments (Carrying Value, Fair Value And Hierarchy Of Financial Instruments) (Details) - USD ($)
$ in Thousands
Sep. 30, 2021
Dec. 31, 2020
Carrying Value [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Mutual fund investments of deferred compensation plans held in trust $ 102,045 $ 86,865
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Mutual fund investments of deferred compensation plans held in trust $ 102,045 $ 86,865