Retirement Benefits (Components Of Net Periodic (Benefit Credit) Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2	$ 2	$ 6	$ 7
Interest cost	14	17	41	50
Expected return on assets	(37)	(37)	(110)	(111)
Recognized actuarial loss	6	5	18	16
Settlement loss	6	3	19	7
Amortization of prior service cost (credit)	0	0	0	0
Net periodic benefit credit	(9)	(10)	(26)	(31)
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0	1	1
Interest cost	4	5	11	15
Expected return on assets	(6)	(6)	(18)	(17)
Recognized actuarial loss	1	3	3	9
Settlement loss	0	0	0	0
Amortization of prior service cost (credit)	(3)	(3)	(9)	(10)
Net periodic benefit credit	$ (4)	$ (1)	$ (12)	$ (2)