Retirement Benefits (Components Of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Non-service Cost or Income Components	$ 116	$ 90	$ 70
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	110	88	100
Interest cost	174	187	169
Expected return on plan assets	(291)	(276)	(276)
Prior service credit	(1)	(1)	(1)
Actuarial (gain) loss	60	25	68
Defined Benefit Plan, Non-service Cost or Income Components	(58)	(65)	(40)
Net periodic benefit cost (income)	52	23	60
Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	19	18	21
Interest cost	39	43	40
Expected return on plan assets	(80)	(77)	(77)
Prior service credit	(4)	(5)	(4)
Actuarial (gain) loss	(9)	(15)	(6)
Defined Benefit Plan, Non-service Cost or Income Components	(54)	(54)	(47)
Net periodic benefit cost (income)	$ (35)	$ (36)	$ (26)