Accumulated Other Comprehensive Income AOCI by Component (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Other Comprehensive Income (Loss) Net of Tax, Period Change [Abstract]
Beginning Balance	$ 234	$ 194
Other comprehensive income (loss), net before reclassifications	1	(1)
Reclassification from AOCI, Current Period, Tax	1	3
Ending Balance	231	187
Equity Method Investments
Other Comprehensive Income (Loss) Net of Tax, Period Change [Abstract]
Beginning Balance	8	9
Other comprehensive income (loss), net before reclassifications	1	(1)
Reclassification from AOCI, Current Period, Tax	0	0
Ending Balance	9	8
Pension and Retiree Health and Welfare Benefit Items
Other Comprehensive Income (Loss) Net of Tax, Period Change [Abstract]
Beginning Balance	226	185
Other comprehensive income (loss), net before reclassifications	0	0
Reclassification from AOCI, Current Period, Tax	1	3
Ending Balance	222	179
Amortization of net loss
Other Comprehensive Income (Loss) Net of Tax, Period Change [Abstract]
Amortization of actuarial losses	(5)	(9)
Amortization of net loss | Equity Method Investments
Other Comprehensive Income (Loss) Net of Tax, Period Change [Abstract]
Amortization of actuarial losses	0	0
Amortization of net loss | Pension and Retiree Health and Welfare Benefit Items
Other Comprehensive Income (Loss) Net of Tax, Period Change [Abstract]
Amortization of actuarial losses	$ (5)	$ (9)