Benefit Plans and Other Postretirement Benefits, Pension Benefits (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jan. 31, 2024	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Operating and maintenance expenses			$ 239,000,000	$ 223,000,000	$ 198,000,000
Target Pension Asset Allocations [Abstract]
annual interest crediting rates [Domain]			4.67	4.86	1.96
annual interest crediting rates [Domain]			4.67	4.86	1.96
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Operating and maintenance expenses				1,000,000
Pension Benefits [Abstract]
Total benefit obligation			112,000,000	112,000,000	141,000,000
Net benefit cost recognized for financial reporting			$ 4,000,000	$ 8,000,000	$ 8,000,000
Expected average long-term rate of return on assets (as a percent)			7.25%	6.60%	6.60%
Target Pension Asset Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage			100.00%	100.00%
Pension Plan [Member] | Subsequent Event
Target Pension Asset Allocations [Abstract]
Payment for Pension Benefits	$ 100,000,000
Pension Plan [Member] | Long-duration fixed income and interest rate swap securities
Target Pension Asset Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage			38.00%	38.00%
Pension Plan [Member] | Domestic and international equity securities
Target Pension Asset Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage			31.00%	33.00%
Pension Plan [Member] | Alternative investments
Target Pension Asset Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage			20.00%	18.00%
Pension Plan [Member] | Short-to-intermediate fixed income securities
Target Pension Asset Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage			9.00%	9.00%
Pension Plan [Member] | Cash
Target Pension Asset Allocations [Abstract]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage			2.00%	2.00%
Forecast [Member] | Pension Plan [Member]
Pension Benefits [Abstract]
Expected average long-term rate of return on assets for next fiscal year (as a percent)		7.25%
Parent Company [Member] | Supplemental Executive Retirement Plan (SERP) and Nonqualified Pension Plan
Pension Benefits [Abstract]
Total benefit obligation			$ 12,000,000	$ 11,000,000
Net benefit cost recognized for financial reporting			$ 2,000,000	$ 17,000,000