Accumulated Other Comprehensive Loss - AOCI Activity (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period			$ 11,840
Other comprehensive income before reclassifications			(125)	$ (6)
Amounts reclassified from accumulated other comprehensive loss			66	109
Other comprehensive (loss) income	$ (170)	$ 135	(59)	103
Balance at end of period	12,219	11,706	12,219	11,706
Defined Benefit Plan | Pension Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period			(1,577)	(2,197)
Other comprehensive income before reclassifications			0	0
Amounts reclassified from accumulated other comprehensive loss			46	71
Other comprehensive (loss) income			46	71
Balance at end of period	(1,531)	(2,126)	(1,531)	(2,126)
Defined Benefit Plan | Post-Retirement Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period			(164)	(272)
Other comprehensive income before reclassifications			0	0
Amounts reclassified from accumulated other comprehensive loss			3	7
Other comprehensive (loss) income			3	7
Balance at end of period	(161)	(265)	(161)	(265)
Foreign Currency Translation Adjustment and Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period			(400)	(265)
Other comprehensive income before reclassifications			(125)	(6)
Amounts reclassified from accumulated other comprehensive loss			0	0
Other comprehensive (loss) income			(125)	(6)
Balance at end of period	(525)	(271)	(525)	(271)
Interest Rate Swap
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period			(17)	(79)
Other comprehensive income before reclassifications			0	0
Amounts reclassified from accumulated other comprehensive loss			17	31
Other comprehensive (loss) income			17	31
Balance at end of period	0	(48)	0	(48)
Accumulated Other Comprehensive Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(2,047)	(2,845)	(2,158)	(2,813)
Other comprehensive (loss) income	(170)	135	(59)	103
Balance at end of period	$ (2,217)	$ (2,710)	$ (2,217)	$ (2,710)