Equity (Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax
Beginning balance	$ 10,962	$ 11,524	$ 10,300	$ 10,102	$ 11,524	$ 10,102
Other comprehensive income (loss) before reclassifications	113		(22)		(179)	(99)
Reclassifications from accumulated other comprehensive loss to net income	(12)		4		(20)	1
Other comprehensive income (loss)	101	(300)	(18)	(80)	(199)	(98)
Ending balance	11,358	10,962	11,221	10,300	$ 11,358	11,221
Accounting Standards Update [Extensible List]					us-gaap:AccountingStandardsUpdate201802Member
Cumulative Effect, Period Of Adoption, Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax
Beginning balance	(3)	2	5	0	$ 2	0
Ending balance		(3)		5
AOCI Including Portion Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax
Beginning balance	(1,122)	(822)	(895)	(785)	(822)	(785)
Other comprehensive income (loss)	101		(18)		(199)	(98)
Ending balance	(1,021)	(1,122)	(913)	(895)	(1,021)	(913)
AOCI Including Portion Attributable to Noncontrolling Interest | Cumulative Effect, Period Of Adoption, Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax
Beginning balance				(30)		(30)
Currency Translation
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax
Beginning balance	(988)	(847)	(901)	(804)	(847)	(804)
Other comprehensive income (loss) before reclassifications	116		4			(65)
Reclassifications from accumulated other comprehensive loss to net income	0		6		0	6
Other comprehensive income (loss)	116		10		(25)	(59)
Ending balance	(872)	(988)	(891)	(901)	(872)	(891)
Currency Translation | Cumulative Effect, Period Of Adoption, Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax
Beginning balance				(28)		(28)
Derivatives
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax
Beginning balance	(127)	32	3	16	32	16
Other comprehensive income (loss) before reclassifications	(3)		(26)		(154)	(34)
Reclassifications from accumulated other comprehensive loss to net income	(12)		(2)		(20)	(5)
Other comprehensive income (loss)	(15)		(28)		(174)	(39)
Ending balance	(142)	(127)	(25)	3	(142)	(25)
Derivatives | Cumulative Effect, Period Of Adoption, Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax
Beginning balance				(2)		(2)
Pension Plan and SERP Liability
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax
Beginning balance	(7)	(7)	3	3	(7)	3
Other comprehensive income (loss) before reclassifications	0		0		0	0
Reclassifications from accumulated other comprehensive loss to net income	0		0		0	0
Other comprehensive income (loss)	0		0		0	0
Ending balance	$ (7)	$ (7)	$ 3	3	$ (7)	3
Pension Plan and SERP Liability | Cumulative Effect, Period Of Adoption, Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax
Beginning balance				$ 0		$ 0