Benefit Plans and Other Postretirement Benefits, Postretirement Benefit Plan Benefit Obligations, Cash Flows and Benefit Costs (Details) - USD ($)	12 Months Ended
	Dec. 31, 2025		Dec. 31, 2024		Dec. 31, 2023
Other Postretirement Benefits Plan [Member]
Change in Projected Benefit Obligation [Roll Forward]
Obligation at Jan. 1	$ 26,000,000		$ 26,000,000
Service cost	1,000,000		1,000,000		$ 1,000,000
Interest cost	1,000,000		1,000,000		1,000,000
Plan participant's contributions	0		1,000,000
Actuarial loss	4,000,000		1,000,000
Benefit payments	(2,000,000)		(4,000,000)
Obligation at Dec. 31	30,000,000		26,000,000		26,000,000
Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1	36,000,000	[1]	36,000,000
Actual return on plan assets	3,000,000		2,000,000
Plan participant's contributions	0		1,000,000
Employer contributions	0		1,000,000
Benefit payments	(2,000,000)		(4,000,000)
Fair value of plan assets at Dec. 31	37,000,000	[1]	36,000,000	[1]	36,000,000
Funded Status of Plans at Dec. 31 [Abstract]
Funded status	7,000,000		10,000,000
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost Have Been Recorded as Follows Based Upon Expected Recovery Rates [Abstract]
Net loss	(15,000,000)		(19,000,000)
Prior service credit	0		0
Total	(15,000,000)		(19,000,000)
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost (Credit) Have Been Recorded as Follows Based Upon Expected Recovery in Rates [Abstract]
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Current Regulatory Assets	0		0
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Noncurrent Regulatory Assets	0		0
Current regulatory liabilities	0		(1,000,000)
Noncurrent regulatory liabilities	(15,000,000)		(18,000,000)
Total	$ (15,000,000)		$ (19,000,000)
Significant Assumptions Used to Measure Benefit Obligations [Abstract]
Discount rate for year-end valuation (as a percent)	5.66%		5.88%
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Pre-65	7.00%		7.00%
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Post-65	7.50%		7.50%
Ultimate health care trend assumption rate (as a percent)	4.50%		4.50%
Period until ultimate trend rate is reached (in years)	$ 8		$ 9
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1,000,000		1,000,000		1,000,000
Interest cost	1,000,000		1,000,000		1,000,000
Expected return on plan assets	(2,000,000)		(2,000,000)		(1,000,000)
Amortization of net loss	(1,000,000)		0		0
Net periodic pension cost	(1,000,000)		0		1,000,000
Defined Benefit Plan, Costs Not Recognized Due To Regulation	0		0		0
Net benefit cost recognized for financial reporting	$ (1,000,000)		$ 0		$ 1,000,000
Significant Assumptions Used to Measure Costs [Abstract]
Discount rate (as a percent)	5.88%		5.54%		5.80%
Expected average long-term increase in compensation level (as a percent)	0.00%		0.00%		0.00%
Expected average long-term rate of return on assets (as a percent)	6.25%		5.00%		5.00%
Pension Plan [Member]
Change in Projected Benefit Obligation [Roll Forward]
Obligation at Jan. 1	$ 409,000,000		$ 425,000,000
Service cost	7,000,000		7,000,000		$ 7,000,000
Interest cost	23,000,000		22,000,000		22,000,000
Plan participant's contributions	0		0
Actuarial loss	12,000,000		(12,000,000)
Benefit payments	(31,000,000)		(33,000,000)
Obligation at Dec. 31	420,000,000		409,000,000		425,000,000
Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1	397,000,000	[2]	420,000,000
Actual return on plan assets	44,000,000		7,000,000
Plan participant's contributions	0		0
Employer contributions	3,000,000		3,000,000
Benefit payments	(31,000,000)		(33,000,000)
Fair value of plan assets at Dec. 31	413,000,000	[2]	397,000,000	[2]	420,000,000
Funded Status of Plans at Dec. 31 [Abstract]
Funded status	(7,000,000)		(12,000,000)
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost Have Been Recorded as Follows Based Upon Expected Recovery Rates [Abstract]
Net loss	162,000,000		165,000,000
Prior service credit	(1,000,000)		(1,000,000)
Total	161,000,000		164,000,000
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost (Credit) Have Been Recorded as Follows Based Upon Expected Recovery in Rates [Abstract]
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Current Regulatory Assets	5,000,000		4,000,000
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Noncurrent Regulatory Assets	156,000,000		160,000,000
Current regulatory liabilities	0		0
Noncurrent regulatory liabilities	0		0
Total	$ 161,000,000		$ 164,000,000
Significant Assumptions Used to Measure Benefit Obligations [Abstract]
Discount rate for year-end valuation (as a percent)	5.78%		5.88%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase	4.25%		4.25%
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 7,000,000		$ 7,000,000		7,000,000
Interest cost	23,000,000		22,000,000		22,000,000
Expected return on plan assets	(32,000,000)		(32,000,000)		(32,000,000)
Amortization of net loss	3,000,000		3,000,000		2,000,000
Net periodic pension cost	1,000,000		0		(1,000,000)
Defined Benefit Plan, Costs Not Recognized Due To Regulation	(2,000,000)		1,000,000		(5,000,000)
Net benefit cost recognized for financial reporting	$ 3,000,000		$ (1,000,000)		$ 4,000,000
Significant Assumptions Used to Measure Costs [Abstract]
Discount rate (as a percent)	5.88%		5.49%		5.80%
Expected average long-term increase in compensation level (as a percent)	4.25%		4.25%		4.25%
Expected average long-term rate of return on assets (as a percent)	7.03%		6.97%		6.96%

[1] See Note 8 for further information on fair value measurement inputs and methods.

[2] See Note 8 for further information on fair value measurement inputs and methods.