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, 2023	Dec. 31, 2022	Dec. 31, 2021
Amounts recognized in Regulatory assets
Regulatory assets	$ 6,317	$ 4,336
Pension plan
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Accumulated benefit obligation, end of year	4,089	4,078
Change in projected benefit obligation
Projected/Accumulated postretirement benefit obligation, beginning of year	4,309	5,857
Service cost	57	95	$ 108
Interest cost	214	166	158
Actuarial (gain) loss	74	(1,252)
Benefits paid	(329)	(278)
Settlements	(7)	(279)
Projected/Accumulated postretirement benefit obligation, end of year	4,318	4,309	5,857
Change in plan assets
Plan assets at fair value, beginning of year	3,897	5,507
Actual return on plan assets	363	(1,062)
Company contributions	36	9
Benefits paid	(329)	(278)
Settlements	(7)	(279)
Plan assets at fair value, end of year	3,960	3,897	$ 5,507
Funded status	(358)	(412)
Amount recorded as:
Current liabilities	(8)	(34)
Noncurrent liabilities	(350)	(378)
Defined benefit plans liabilities	(358)	(412)
Amounts recognized in Accumulated other comprehensive income (loss), pre-tax
Net actuarial loss	76	85
Amounts recognized in Accumulated other comprehensive income (loss), pre-tax	76	85
Amounts recognized in Regulatory assets
Net actuarial loss	1,426	1,369
Prior service credit	(5)	(7)
Regulatory assets	$ 1,421	$ 1,362