Shareholders' Equity - Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	$ 11,984	$ 10,748	$ 11,659	$ 10,294
Other comprehensive (loss) income, net of tax	(10)	(228)	32	(168)
Balance at end of period	12,385	10,976	12,385	10,976
AOCI Attributable to Parent [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	(1,024)	(708)	(1,066)	(768)
Balance at end of period	(1,034)	(936)	(1,034)	(936)
Unrealized Gain (Loss) on Hedges [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	(6)	17	9	16
Other comprehensive (loss) income, net of tax	(18)	17	(33)	18
Balance at end of period	(24)	34	(24)	34
Defined Benefit Plans [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	1	1	1	1
Other comprehensive (loss) income, net of tax	0	0	0	0
Balance at end of period	1	1	1	1
Foreign Currency Translation Adjustment [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	(1,019)	(726)	(1,076)	(785)
Other comprehensive (loss) income, net of tax	8	(245)	65	(186)
Balance at end of period	$ (1,011)	$ (971)	$ (1,011)	$ (971)