Accumulated Other Comprehensive Loss - AOCI Activity (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period			$ 417
Other comprehensive income (loss) before reclassifications			(5)	$ 20
Amounts reclassified from accumulated other comprehensive loss			29	26
Other comprehensive income	$ 13	$ 16	24	46
Balance at end of period	466	2,221	466	2,221
Defined Benefit Plan | Pension Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period			(1,045)	(985)
Other comprehensive income (loss) before reclassifications			0	0
Amounts reclassified from accumulated other comprehensive loss			38	36
Other comprehensive income			38	36
Balance at end of period	(1,007)	(949)	(1,007)	(949)
Defined Benefit Plan | Post-Retirement Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period			276	308
Other comprehensive income (loss) before reclassifications			0	0
Amounts reclassified from accumulated other comprehensive loss			(9)	(10)
Other comprehensive income			(9)	(10)
Balance at end of period	267	298	267	298
Foreign Currency Translation Adjustment and Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period			(41)	(422)
Other comprehensive income (loss) before reclassifications			(5)	20
Amounts reclassified from accumulated other comprehensive loss			0	0
Other comprehensive income			(5)	20
Balance at end of period	(46)	(402)	(46)	(402)
Accumulated Other Comprehensive Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(799)	(1,069)	(810)	(1,099)
Other comprehensive income	13	16	24	46
Balance at end of period	$ (786)	$ (1,053)	$ (786)	$ (1,053)