Accumulated Other Comprehensive Income AOCI by Component (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 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	2	1
Ending Balance	576	231
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	2	1
Ending Balance	566	222
Amortization of net (gains) losses
Other Comprehensive Income (Loss) Net of Tax, Period Change [Abstract]
Amortization of actuarial (gains) losses	(8)	(5)
Amortization of net (gains) losses | Equity Method Investments
Other Comprehensive Income (Loss) Net of Tax, Period Change [Abstract]
Amortization of actuarial (gains) losses	0	0
Amortization of net (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	$ (8)	$ (5)