Retirement Benefits (Components Of Net Periodic (Benefit Credit) Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 2	$ 0	$ 4
Interest cost	16	13	32	27
Expected return on assets	(35)	(36)	(69)	(73)
Recognized actuarial loss	4	6	8	12
Settlement loss	2	7	4	13
Amortization of prior service cost (credit)	0	0	0	0
Net periodic benefit credit	(13)	(8)	(25)	(17)
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	1	0	1
Interest cost	4	3	8	7
Expected return on assets	(6)	(6)	(11)	(12)
Recognized actuarial loss	1	1	1	2
Settlement loss	0	0	0	0
Amortization of prior service cost (credit)	(3)	(3)	(6)	(6)
Net periodic benefit credit	$ (4)	$ (4)	$ (8)	$ (8)