Postretirement Plans (Schedule Of Key Information For All Plans With ABO In Excess Of Plan Assets) (Details) - Pension Plans [Member] - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Accumulated Benefit Obligation	$ 74,337	$ 70,466
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets	61,502	55,907
Projected benefit obligation	$ 76,057	$ 72,325