Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 12,905
Other comprehensive loss, net of tax	(101)	$ (179)
Net other comprehensive loss	(101)	(179)
Balance at end of period	13,197	12,738
Pension Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(13)	2
Other comprehensive loss, net of tax	0	0
Net other comprehensive loss	0	0
Balance at end of period	(13)	2
Foreign Currency Translation Adjustment and Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(221)	(181)
Other comprehensive loss, net of tax	(101)	(179)
Net other comprehensive loss	(101)	(179)
Balance at end of period	(322)	(360)
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(234)	(179)
Balance at end of period	$ (335)	$ (358)