Retirement Benefits (Components Of Net Periodic (Benefit Credit) Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 13	$ 16	$ 25	$ 32
Expected return on assets	(29)	(35)	(69)	(69)
Recognized actuarial loss	6	4	12	8
Settlement loss	10	2	15	4
Amortization of prior service cost (credit)	0	0	0	0
Net periodic benefit credit	0	(13)	(17)	(25)
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	2	4	5	8
Expected return on assets	(6)	(6)	(12)	(11)
Recognized actuarial loss	0	1	0	1
Settlement loss	0	0	0	0
Amortization of prior service cost (credit)	(2)	(3)	(4)	(6)
Net periodic benefit credit	$ (6)	$ (4)	$ (11)	$ (8)