Accumulated Other Comprehensive Loss - AOCI Activity (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period			$ 464
Other comprehensive loss before reclassifications			3	$ (5)
Amounts reclassified from accumulated other comprehensive loss			41	29
Other comprehensive income	$ 21	$ 13	44	24
Balance at end of period	(595)	466	(595)	466
Accumulated Other Comprehensive Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(700)	(799)	(723)	(810)
Other comprehensive income	21	13	44	24
Balance at end of period	(679)	(786)	(679)	(786)
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			54	38
Other comprehensive income			54	38
Balance at end of period	(949)	(1,007)	(949)	(1,007)
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			(13)	(9)
Other comprehensive income			(13)	(9)
Balance at end of period	307	267	307	267
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	(5)
Amounts reclassified from accumulated other comprehensive loss			0	0
Other comprehensive income			3	(5)
Balance at end of period	$ (37)	$ (46)	$ (37)	$ (46)