Pension Plans and Other Postretirement Benefit Plans - Change in Benefit Obligation and Plan Assets (Details) - USD ($) $ in Millions		1 Months Ended	12 Months Ended
		Apr. 30, 2024	Dec. 31, 2024		Dec. 31, 2023		Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Curtailments		$ 1
Other current liabilities			$ (15)		$ (14)
Non-current liabilities			(75)		(90)
Pension Plan and SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year			585	[1]	558
Service cost	[2]		16		14		$ 24
Interest cost			$ 34		$ 33		27
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]			Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses		Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses
Actuarial (gain)/loss	[3]		$ 2		$ 21
Benefits paid			(36)		(41)
Curtailments			(1)
Benefit obligation as of end of year			600	[1]	585	[1]	558
Fair value of plan assets as of beginning of year			590	[1]	541
Actual return on plan assets			42		79
Employer contributions			10		10
Benefits paid			(34)		(40)
Fair value of plan assets as of end of year			608	[1]	590	[1]	541
Funded status			8		5
Other non-current assets			35		33
Other current liabilities			(2)		(2)
Non-current liabilities			(25)		(26)
Net amount recognized			8		5
Accumulated pension benefit obligation	[1]		522		514
Unrecognized prior service cost (credit)			3		4
Unrecognized net actuarial loss			70		69
Total			73		73
Less regulatory asset			(73)		(72)
Accumulated other comprehensive loss for unfunded benefit obligation for pensions and other postretirement benefit plans			$ 0		$ 1
Discount rate for benefit obligation			6.13%		5.86%
Discount rate for annual expense			5.86%		6.10%
Expected long-term return on plan assets			7.80%		8.30%
Rate of compensation increase			5.19%		4.87%
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year			$ 122	[1]	$ 116
Service cost	[2]		3		2		4
Interest cost			$ 7		$ 7		6
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]			Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses		Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses
Actuarial (gain)/loss	[3]		$ (9)		$ 4
Benefits paid			(6)		(7)
Benefit obligation as of end of year			117	[1]	122	[1]	116
Fair value of plan assets as of beginning of year			58	[1]	49
Actual return on plan assets			9		9
Fair value of plan assets as of end of year			67	[1]	58	[1]	$ 49
Funded status			(50)		(64)
Other current liabilities			(1)		(1)
Non-current liabilities			(49)		(63)
Net amount recognized			(50)		(64)
Unrecognized prior service cost (credit)			0		(1)
Unrecognized net actuarial loss			2		13
Total			2		12
Less regulatory asset			(2)		(13)
Accumulated other comprehensive loss for unfunded benefit obligation for pensions and other postretirement benefit plans			$ 0		$ (1)
Discount rate for benefit obligation			6.09%		5.83%
Discount rate for annual expense			5.83%		6.10%
Expected long-term return on plan assets			6.70%		7.20%
Other Postretirement Benefits [Member] | Pre-Age 65 [Member]
Defined Benefit Plan Disclosure [Line Items]
Medical cost trend – initial			6.50%		6.50%
Medical cost trend – ultimate			5.00%		5.00%
Ultimate medical cost trend year			2031		2030
Other Postretirement Benefits [Member] | Post-Age 65 [Member]
Defined Benefit Plan Disclosure [Line Items]
Medical cost trend – initial			6.50%		6.50%
Medical cost trend – ultimate			5.00%		5.00%
Ultimate medical cost trend year			2031		2030
Other Postretirement Benefits [Member] | Retirees [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year			$ 68
Benefit obligation as of end of year			67		$ 68
Other Postretirement Benefits [Member] | Fully eligible employees [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year			16
Benefit obligation as of end of year			16		16
Other Postretirement Benefits [Member] | Other participants [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year			38
Benefit obligation as of end of year			$ 34		$ 38

[1] As of December 31, 2024, the SERP had a projected benefit obligation of $27 million and an accumulated benefit obligation of $26 million, with no plan assets.

[2] Total service cost in the table above is recorded to the same accounts as labor expense. Labor and benefits expense is recorded to various projects based on whether the work is a capital project or an operating expense. Approximately 45 percent of all labor and benefits is capitalized to utility property and 55 percent is expensed to utility other operating expenses.

[3] The change in the pension benefit obligation related to actuarial loss is primarily related to changes in demographic experience, partially offset by financial assumption changes.