Retirement Benefits- Narrative (Details)			3 Months Ended	11 Months Ended	12 Months Ended
	Mar. 02, 2022 USD ($)	Feb. 01, 2022 USD ($)	Mar. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2023 USD ($) servicePeriod	Dec. 31, 2022 USD ($) servicePeriod	Dec. 31, 2021 USD ($) servicePeriod
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Increase (Decrease) in Obligation, Pension Benefits			$ 27,000,000	$ 921,000,000
Benefit obligation increase (decrease) reflecting actual census data			2,000,000	893,000,000
Accumulated Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Tax		$ 1,994,000,000	10,000,000
Regulatory asset increase (decrease) due to updated valuation adjustment			18,000,000	14,000,000
Defined benefit plan, amounts increased (decrease) in regulatory liabilities, before tax			$ 1,000,000	5,000,000
Defined Contribution Plan, Employer Discretionary Contribution Amount					$ 109,000,000	$ 91,000,000	$ 90,000,000
Payment for Pension and Other Postretirement Benefits					129,000,000	616,000,000	665,000,000
Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accumulated Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Tax				(2,631,000,000)	0	(2,631,000,000)	0
Regulatory asset increase (decrease) due to updated valuation adjustment					$ 240,000,000	$ (435,000,000)	$ (581,000,000)
Expected return on plan assets					7.00%	7.00%	7.00%
Discount rate					5.53%	3.24%	2.58%
Defined Contribution Plan, Employer Discretionary Contribution Amount					$ 93,000,000
Payment for Pension and Other Postretirement Benefits	$ 33,000,000	$ 207,000,000			$ 75,000,000	$ 570,000,000	$ 343,000,000
Average Remaining Service Period Of Active Participants in Plan | servicePeriod					12.6	12.5	12.4
Pension Plan, Defined Benefit [Member] | Fair Value, Concentration of Risk, All Financial Instruments | Credit Concentration Risk
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Concentration of Risk, Investments					$ 0
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accumulated Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Tax				$ (43,000,000)	0	$ (43,000,000)	$ 0
Regulatory asset increase (decrease) due to updated valuation adjustment					$ 38,000,000	$ (233,000,000)	$ (144,000,000)
Expected return on plan assets					6.50%	6.44%	6.46%
Discount rate					5.51%	3.20%	2.51%
Payment for Pension and Other Postretirement Benefits					$ 54,000,000	$ 42,000,000	$ 63,000,000
Other Postretirement Benefit Plan, Defined Benefit [Member] | Benefit Eligibility Age
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Average Remaining Service Period Of Active Participants in Plan | servicePeriod					8.1	7.9	7.6
Other Postretirement Benefit Plan, Defined Benefit [Member] | Expected Retirement Period
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Average Remaining Service Period Of Active Participants in Plan | servicePeriod					9.3	9.1	8.8
Change in Assumptions for Defined Benefit Plans [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected return on plan assets					7.00%
Change in Assumptions for Defined Benefit Plans [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected return on plan assets					6.50%
Assets [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actual Asset Returns					7.73%
Assets [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actual Asset Returns					9.20%