Retirement Plans (Schedule Of Allocation Of Plan Assets) (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Percentage of Plan Assets	100.00%	100.00%
Weighted Average Expected Long-term Rates of Return	5.50%	5.50%	5.50%
Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted Average Expected Long-term Rates of Return	4.10%	4.20%
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted Average Expected Long-term Rates of Return	5.50%	5.60%
Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of Plan Assets	0.20%	0.20%
Cash Equivalents [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	0.00%	0.00%
Cash Equivalents [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	1.00%	1.00%
Equity Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of Plan Assets	26.40%	18.10%
Equity Mutual Funds [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	20.00%	15.00%
Weighted Average Expected Long-term Rates of Return	6.20%	5.90%
Equity Mutual Funds [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	30.00%	25.00%
Weighted Average Expected Long-term Rates of Return	8.70%	8.30%
Fixed Income Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of Plan Assets	73.40%	81.70%
Fixed Income Mutual Funds [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	70.00%	75.00%
Weighted Average Expected Long-term Rates of Return	3.30%	3.80%
Fixed Income Mutual Funds [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	80.00%	85.00%
Weighted Average Expected Long-term Rates of Return	4.40%	5.00%