Accumulated Other Comprehensive Loss - AOCI Activity (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 417	$ 10,374
Other comprehensive (loss) income before reclassifications	30	(122)
Amounts reclassified from accumulated other comprehensive income (loss)	57	411
Other comprehensive income	87	289	$ 1,059
Balance at end of period	464	417	10,374
Defined Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(769)	(677)
Other comprehensive (loss) income before reclassifications	29	(121)
Amounts reclassified from accumulated other comprehensive income (loss)	57	29
Other comprehensive income	86	(92)
Balance at end of period	(683)	(769)	(677)
Defined Benefit Plans | Pension Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(1,045)	(985)
Other comprehensive (loss) income before reclassifications	(34)	(110)
Amounts reclassified from accumulated other comprehensive income (loss)	76	50
Other comprehensive income	42	(60)
Balance at end of period	(1,003)	(1,045)	(985)
Defined Benefit Plans | Post-Retirement Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	276	308
Other comprehensive (loss) income before reclassifications	63	(11)
Amounts reclassified from accumulated other comprehensive income (loss)	(19)	(21)
Other comprehensive income	44	(32)
Balance at end of period	320	276	308
Foreign Currency Translation Adjustment and Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(41)	(422)
Other comprehensive (loss) income before reclassifications	1	(1)
Amounts reclassified from accumulated other comprehensive income (loss)	0	382
Other comprehensive income	1	381
Balance at end of period	(40)	(41)	(422)
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(810)	(1,099)	(2,158)
Other comprehensive income	87	289	1,059
Balance at end of period	$ (723)	$ (810)	$ (1,099)