Retirement Benefits (Components Of Net Periodic Benefit Cost (Benefit Credit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Settlement loss	$ 9	$ 5	$ 7
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	8	10
Interest cost	62	55	66
Expected return on assets	(138)	(147)	(147)
Recognized actuarial loss	17	22	22
Settlement loss	9	5	7
Net periodic (benefit credit) benefit cost	(50)	(57)	(42)
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	1
Interest cost	15	15	21
Expected return on assets	(22)	(24)	(23)
Recognized actuarial loss	2	3	11
Amortization of prior service credit	(12)	(12)	(13)
Net periodic (benefit credit) benefit cost	$ (16)	$ (17)	$ (3)