Accumulated Other Comprehensive Income AOCI by Component (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 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	2	5
Ending Balance	227	180
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	2	5
Ending Balance	218	172
Amortization of net loss
Other Comprehensive Income (Loss) Net of Tax, Period Change [Abstract]
Amortization of actuarial (gains) losses	(10)	(18)
Amortization of net loss | Equity Method Investments
Other Comprehensive Income (Loss) Net of Tax, Period Change [Abstract]
Amortization of actuarial (gains) 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 (gains) losses	$ (10)	$ (18)