Retirement Benefits (Schedule Of Potential Changes In Key Assumptions) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($)
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service Cost and Interest Cost, .25% decrease in discount rate	$ (1)
Defined Benefit Plan Effect Of a Quarter-Percentage Point Decrease of the Discount Rate On the Expected Return on Assets	0
Benefit Obligation, .25% decrease in discount rate	195
Defined Benefit Plan Effect of a Quarter-Percentage Decrease of Return On Assets On the Service and Interest Cost Components	0
Defined Benefit Plan Effect Of a Quarter-Percentage Point Decrease of Return on Assets on the Expected Return on Assets	10
Defined Benefit Plan Effect of a Quarter-Percentage Decrease of Return on Assets on the Projected Benefit Obligation	0
Service Cost and Interest Cost, .25% increase in salary rate	2
Defined Benefit Plan Effect Of a Quarter-Percentage Point Increase of the assumed annual salary increase Rate On the Expected Return on Assets	0
Benefit Obligation, .25% increase in salary rate	20
Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service Cost and Interest Cost, .25% decrease in discount rate	0
Defined Benefit Plan Effect Of a Quarter-Percentage Point Decrease of the Discount Rate On the Expected Return on Assets	0
Benefit Obligation, .25% decrease in discount rate	42
Defined Benefit Plan Effect of a Quarter-Percentage Decrease of Return On Assets On the Service and Interest Cost Components	0
Defined Benefit Plan Effect Of a Quarter-Percentage Point Decrease of Return on Assets on the Expected Return on Assets	3
Defined Benefit Plan Effect of a Quarter-Percentage Decrease of Return on Assets on the Projected Benefit Obligation	0
Service Cost and Interest Cost, .25% increase in salary rate	0
Defined Benefit Plan Effect Of a Quarter-Percentage Point Increase of the assumed annual salary increase Rate On the Expected Return on Assets	0
Benefit Obligation, .25% increase in salary rate	$ 0