Accumulated Other Comprehensive Income AOCI by Component (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024
Other Comprehensive Income (Loss) Net of Tax, Period Change [Abstract]
Beginning Balance	$ 581	$ 234
Other comprehensive income (loss), net before reclassifications	1	1
Reclassification from AOCI, Current Period, Tax	6	3
Ending Balance	565	223
Equity Method Investments
Other Comprehensive Income (Loss) Net of Tax, Period Change [Abstract]
Beginning Balance	9	8
Other comprehensive income (loss), net before reclassifications	1	1
Reclassification from AOCI, Current Period, Tax	0	0
Ending Balance	10	9
Pension and Retiree Health and Welfare Benefit Items
Other Comprehensive Income (Loss) Net of Tax, Period Change [Abstract]
Beginning Balance	572	226
Other comprehensive income (loss), net before reclassifications	0	0
Reclassification from AOCI, Current Period, Tax	6	3
Ending Balance	555	214
Amortization of actuarial (gains) losses
Other Comprehensive Income (Loss) Net of Tax, Period Change [Abstract]
Amortization of actuarial (gains) losses	(23)	(15)
Amortization of actuarial (gains) losses | Equity Method Investments
Other Comprehensive Income (Loss) Net of Tax, Period Change [Abstract]
Amortization of actuarial (gains) losses	0	0
Amortization of actuarial (gains) losses | Pension and Retiree Health and Welfare Benefit Items
Other Comprehensive Income (Loss) Net of Tax, Period Change [Abstract]
Amortization of actuarial (gains) losses	$ (23)	$ (15)