Retirement Benefits (Funded Status Of Benefit Plans And Amounts Included In Regulatory Assets And OCI) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Change in plan assets:
Funded status – deficiency (surplus)	$ (481)	$ (551)
Amounts recognized in the balance sheet consist of:
Noncurrent liability	558	545
Net liability (asset) recognized	481	551
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation at end of year	4,258	4,577
Change in benefit obligation:
Net benefit obligation at beginning of year	4,827	4,518
Service cost	100	93	$ 81
Interest cost	169	179	185
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment	0	0
Participant contributions	0	0
Actuarial (gain) loss	(401)	255
Benefits paid	(236)	(218)
Net benefit obligation at end of year	4,459	4,827	4,518
Change in plan assets:
Fair value of plan assets at beginning of year	4,293	3,813
Actual return on plan assets	(218)	634
Employer contributions	60	64	57
Participant contributions	0	0
Benefits paid	(236)	(218)
Fair value of plan assets at end of year	3,899	4,293	3,813
Funded status – deficiency (surplus)	560	534
Accrued benefit cost (asset) at December 31	560	534
Amounts recognized in the balance sheet consist of:
Noncurrent asset	0	0
Current liability(c)	2	3
Noncurrent liability	558	531
Net liability (asset) recognized	560	534
Amounts recognized in regulatory assets consist of:
Net actuarial (gain) loss	393	374
Prior service credit	(2)	(3)
Amounts (pretax) recognized in accumulated OCI consist of:
Net actuarial loss	35	30
Total	426	401
Postretirement Benefits
Change in benefit obligation:
Net benefit obligation at beginning of year	1,240	1,170
Service cost	21	21	19
Interest cost	40	47	50
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment	(49)	0
Participant contributions	9	8
Actuarial (gain) loss	(163)	53
Benefits paid	(64)	(59)
Net benefit obligation at end of year	1,034	1,240	1,170
Change in plan assets:
Fair value of plan assets at beginning of year	1,223	1,101
Actual return on plan assets	(57)	171
Employer contributions	2	2	2
Participant contributions	9	8
Benefits paid	(64)	(59)
Fair value of plan assets at end of year	1,113	1,223	$ 1,101
Funded status – deficiency (surplus)	(79)	17
Accrued benefit cost (asset) at December 31	(79)	17
Amounts recognized in the balance sheet consist of:
Noncurrent asset	(79)	0
Current liability(c)	0	3
Noncurrent liability	0	14
Net liability (asset) recognized		17
Amounts recognized in regulatory assets consist of:
Net actuarial (gain) loss	(91)	(69)
Prior service credit	(48)	(3)
Amounts (pretax) recognized in accumulated OCI consist of:
Net actuarial loss	3	2
Total	$ (136)	$ (70)