Accumulated Other Comprehensive Income (Loss) - Summary of Changes in Accumulated Other Comprehensive Income (Loss) by Component (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	$ (2,417)	$ (2,452)	$ (2,593)	$ (1,808)	$ (1,241)	$ (2,195)	$ (2,593)	$ (2,195)
Total other comprehensive (loss) income, net of tax	110	(35)	63	(1)	(45)	(184)	138	(230)
Ending balance	(2,264)	(2,417)	(2,452)	(2,456)	(1,808)	(1,241)	(2,264)	(2,456)
Foreign Exchange Translation Adjustment
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance			86			284	86	284
Other comprehensive income (loss) before reclassifications							127	(251)
Total other comprehensive (loss) income, net of tax							127	(251)
Ending balance	213			33			213	33
Changes in Fair Value of Effective Cash Flow Hedges
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance						(35)		(35)
Other comprehensive income (loss) before reclassifications							9	3
Amounts reclassified from accumulated other comprehensive income (loss)							1	21
Total other comprehensive (loss) income, net of tax							10	24
Ending balance	10			(11)			10	(11)
Changes in Currency Basis Reserve
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive income (loss) before reclassifications								(3)
Total other comprehensive (loss) income, net of tax								(3)
Ending balance				(3)				(3)
Pension Adjustments
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance			(13)			(11)	(13)	(11)
Amounts reclassified from accumulated other comprehensive income (loss)							1
Total other comprehensive (loss) income, net of tax							1
Ending balance	(12)			(11)			(12)	(11)
Total Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	101	136	73	9	54	238	73	238
Other comprehensive income (loss) before reclassifications							136	(251)
Amounts reclassified from accumulated other comprehensive income (loss)							2	21
Total other comprehensive (loss) income, net of tax	110	(35)	63	(1)	(45)	(184)	138	(230)
Ending balance	$ 211	$ 101	$ 136	$ 8	$ 9	$ 54	$ 211	$ 8