Accumulated Other Comprehensive Income Reclassifications out of AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Balance	$ 234	$ 194	$ 353
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	362	67	(163)
Reclassification AOCI, Tax	5	9	(1)
Balance	581	234	194
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent	115	21	56
Amortization of net gain
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income	(20)
Amortization of prior service credits
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income		(36)
Settlement (gain) lossa
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income			(1)
Equity Method Investments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Balance	8	9	(3)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	1	(1)	12
Reclassification AOCI, Tax	0	0	0
Balance	9	8	9
Equity Method Investments | Amortization of net gain
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income	0
Equity Method Investments | Amortization of prior service credits
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income		0
Equity Method Investments | Settlement (gain) lossa
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income			0
Pension and Retiree Health and Welfare Benefit Items
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Balance	226	185	356
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	361	68	(175)
Reclassification AOCI, Tax	5	9	(1)
Balance	572	226	185
Pension and Retiree Health and Welfare Benefit Items | Amortization of net gain
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income	$ (20)
Pension and Retiree Health and Welfare Benefit Items | Amortization of prior service credits
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income		$ (36)
Pension and Retiree Health and Welfare Benefit Items | Settlement (gain) lossa
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income			$ (1)