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Retirement Plans And Other Postretirement Benefits (Schedule Of Amounts Recognized Before Related Deferred Income Taxes In Accumulated Other Comprehensive Income) (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Pension Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Prior service cost (benefit) $ 5 $ 10 $ 18
Net actuarial (gain) loss 144,377 145,782 153,570
Other Post-Retirement Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Prior service cost (benefit) 0 0 0
Net actuarial (gain) loss $ (1,238) $ (1,756) $ (1,616)