Retirement Benefits (Components Of Net Periodic Benefit Cost (Benefit Credit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Settlement loss	$ 29	$ 9	$ 5
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0	8
Interest cost	47	62	55
Expected return on assets	(138)	(138)	(147)
Recognized actuarial loss	24	17	22
Settlement loss	29	9	5
Net periodic (benefit credit) benefit cost	(38)	(50)	(57)
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	1
Interest cost	10	15	15
Expected return on assets	(25)	(22)	(24)
Recognized actuarial loss	0	2	3
Amortization of prior service credit	(7)	(12)	(12)
Net periodic (benefit credit) benefit cost	$ (21)	$ (16)	$ (17)