Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 13,545
Other comprehensive loss, net of tax	(179)	$ (115)
Net other comprehensive loss	(179)	(115)
Balance at end of period	12,738	13,653
Pension Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	2	5
Other comprehensive loss, net of tax	0	0
Net other comprehensive loss	0	0
Balance at end of period	2	5
Foreign Currency Translation Adjustment and Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(181)	(176)
Other comprehensive loss, net of tax	(179)	(115)
Net other comprehensive loss	(179)	(115)
Balance at end of period	(360)	(291)
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	(179)	(171)
Balance at end of period	$ (358)	$ (286)