Accumulated Other Comprehensive Loss - AOCI Activity (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 464
Other comprehensive loss before reclassifications	3	$ (4)
Amounts reclassified from accumulated other comprehensive loss	20	15
Other comprehensive income	23	11
Balance at end of period	289	504
Accumulated Other Comprehensive Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(723)	(810)
Other comprehensive income	23	11
Balance at end of period	(700)	(799)
Defined Benefit Plan | Pension Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(1,003)	(1,045)
Other comprehensive loss before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive loss	26	20
Other comprehensive income	26	20
Balance at end of period	(977)	(1,025)
Defined Benefit Plan | Post-Retirement Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	320	276
Other comprehensive loss before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive loss	(6)	(5)
Other comprehensive income	(6)	(5)
Balance at end of period	314	271
Foreign Currency Translation Adjustment and Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(40)	(41)
Other comprehensive loss before reclassifications	3	(4)
Amounts reclassified from accumulated other comprehensive loss	0	0
Other comprehensive income	3	(4)
Balance at end of period	$ (37)	$ (45)