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Retirement, Other Postretirement Benefits, And Defined Contribution Plans (Plan Assets, Asset Allocations Targets) (Details)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Domestic Equity Securities [Member] | Other Postretirement Taxable and Non-Taxable Assets [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Target 27.00%  
Range, Minimum 22.00%  
Range, Maximum 32.00%  
Postretirement Asset Allocation 30.00% 40.00%
International Equity Securities [Member] | Other Postretirement Taxable and Non-Taxable Assets [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Target 18.00%  
Range, Minimum 13.00%  
Range, Maximum 23.00%  
Postretirement Asset Allocation 20.00% 27.00%
Fixed Income Securities [Member] | Other Postretirement Taxable and Non-Taxable Assets [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Target 55.00%  
Range, Minimum 50.00%  
Range, Maximum 60.00%  
Postretirement Asset Allocation 50.00% 33.00%
Other Securities [Member] | Other Postretirement Taxable and Non-Taxable Assets [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Target 0.00%  
Range, Minimum 0.00%  
Range, Maximum 5.00%  
Postretirement Asset Allocation 0.00% 0.00%
Qualified Pension Plans [Member] | Domestic Equity Securities [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Target 45.00%  
Range, Minimum 37.00%  
Range, Maximum 53.00%  
Postretirement Asset Allocation 45.00% 46.00%
Qualified Pension Plans [Member] | International Equity Securities [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Target 20.00%  
Range, Minimum 16.00%  
Range, Maximum 24.00%  
Postretirement Asset Allocation 20.00% 20.00%
Qualified Pension Plans [Member] | Fixed Income Securities [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Target 35.00%  
Range, Minimum 32.00%  
Range, Maximum 38.00%  
Postretirement Asset Allocation 34.00% 33.00%
Qualified Pension Plans [Member] | Other Securities [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Target 0.00%  
Range, Minimum 0.00%  
Range, Maximum 10.00%  
Postretirement Asset Allocation 1.00% 1.00%