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Retirement Benefits (Accumulated Benefit Obligation In Excess of Plan Assets) (Details) - USD ($)
$ in Millions
Dec. 31, 2019
Dec. 31, 2018
Other Postretirement Benefits    
Defined Benefit Plan Disclosure [Line Items]    
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets   $ 241
Funded Plans [Member] | Pension Benefits    
Defined Benefit Plan Disclosure [Line Items]    
Defined Benefit Plan, Pension Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Projected Benefit Obligation $ 51 0
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets   1
Unfunded Plans [Member] | Pension Benefits    
Defined Benefit Plan Disclosure [Line Items]    
Defined Benefit Plan, Pension Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Projected Benefit Obligation $ 34 37
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets   $ 0