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, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	$ 150,267	$ 150,047	$ 132,751
Other Post-Retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	$ 86	$ (824)	$ (1,821)

Amount, before tax, after reclassification adjustment, of increase (decrease) in accumulated other comprehensive income from gain (loss) of defined benefit plan.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 20
-Section 50
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