Retirement Benefits (Reconciliation Of The Benefit Obligation) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Benefits [Member]
Reconciliation of benefit obligation
Benefit obligation at beginning of year	$ 1,880	$ 1,743
Service cost	0	0	$ 8
Interest cost	47	62	55
Plan participant contributions	0	0
Actuarial loss (gain)	219	200
Settlements	(80)	(35)
Benefits paid	(57)	(90)
Benefit obligation at end of year	2,009	1,880	1,743
Other Benefits [Member]
Reconciliation of benefit obligation
Benefit obligation at beginning of year	423	431
Service cost	1	1	1
Interest cost	10	15	15
Plan participant contributions	18	17
Actuarial loss (gain)	(15)	5
Settlements	0	0
Benefits paid	(38)	(46)
Benefit obligation at end of year	$ 399	$ 423	$ 431