Retirement Benefits (Components Of Net Periodic (Benefit Credit) Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 0	$ 0	$ 0
Interest cost	12	15	37	47
Expected return on assets	(35)	(35)	(104)	(104)
Recognized actuarial loss	6	5	18	13
Settlement loss	6	4	21	8
Amortization of prior service cost (credit)	0	0	0	0
Net periodic benefit credit	(11)	(11)	(28)	(36)
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	1	0	1
Interest cost	3	3	8	11
Expected return on assets	(6)	(6)	(18)	(17)
Recognized actuarial loss	0	1	0	2
Settlement loss	0	0	0	0
Amortization of prior service cost (credit)	(2)	(3)	(6)	(9)
Net periodic benefit credit	$ (5)	$ (4)	$ (16)	$ (12)