Retirement Benefits and Trusteed Assets (Pension Plan - Reconciliation of Obligations, Assets and Funded Status of Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Change in projected benefit obligation
Plan amendments	$ 4	$ 0
Amounts recognized in Regulatory assets
Regulatory assets	3,677	4,254
Pension plan
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Accumulated benefit obligation, end of year	5,448	5,843
Change in projected benefit obligation
Projected/Accumulated postretirement benefit obligation, beginning of year	6,304	5,810
Service cost	108	99	$ 84
Interest cost	158	186	219
Actuarial (gain) loss	(255)	619
Special termination benefits	0	3
Benefits paid	(414)	(353)
Settlements	(48)	(60)
Projected/Accumulated postretirement benefit obligation, end of year	5,857	6,304	5,810
Change in plan assets
Plan assets at fair value, beginning of year	5,497	4,993
Actual return on plan assets	460	815
Company contributions	12	102
Benefits paid	(414)	(353)
Settlements	(48)	(60)
Plan assets at fair value, end of year	5,507	5,497	$ 4,993
Funded status	(350)	(807)
Amount recorded as:
Current liabilities	(11)	(10)
Noncurrent liabilities	(339)	(797)
Defined benefit plans liabilities	(350)	(807)
Amounts recognized in Accumulated other comprehensive income (loss), pre-tax
Net actuarial loss	126	142
Prior service cost	1	3
Amounts recognized in Accumulated other comprehensive income (loss), pre-tax	127	145
Amounts recognized in Regulatory assets
Net actuarial loss	1,381	1,949
Prior service credit	(9)	(11)
Regulatory assets	$ 1,372	$ 1,938