Equity - Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	$ 16,994	$ 17,146	$ 17,286	$ 17,231
Other comprehensive income (loss)	48	(39)	(30)	(33)
Ending Balance	19,052	17,185	19,052	17,185
Accumulated other comprehensive loss
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(321)	(309)	(243)	(315)
Other comprehensive income (loss)	49	(40)	(29)	(34)
Income tax benefit (expense)	(1)	1	(1)	1
Other comprehensive income (loss)	48	(39)	(30)	(33)
Ending Balance	(273)	(348)	(273)	(348)
Foreign currency translation adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(255)	(220)	(177)	(227)
Other comprehensive income (loss)	49	(40)	(29)	(33)
Income tax benefit (expense)	(1)	1	(1)	1
Other comprehensive income (loss)	48	(39)	(30)	(32)
Ending Balance	(207)	(259)	(207)	(259)
Comprehensive income from equity method investment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	1	1	1	2
Other comprehensive income (loss)	0	0	0	(1)
Income tax benefit (expense)	0	0	0	0
Other comprehensive income (loss)	0	0	0	(1)
Ending Balance	1	1	1	1
Employee benefit plans adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(67)	(90)	(67)	(90)
Other comprehensive income (loss)	0	0	0	0
Income tax benefit (expense)	0	0	0	0
Other comprehensive income (loss)	0	0	0	0
Ending Balance	$ (67)	$ (90)	$ (67)	$ (90)