Accumulated Other Comprehensive Loss - Summary of Accumulated Other Comprehensive Loss (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
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 1,950	$ 2,044	$ 2,159	$ 2,234	$ 2,294	$ 2,348	$ 2,159	$ 2,348
Other comprehensive income (loss) before reclassifications							(56)	7
Amounts reclassified from accumulated other comprehensive loss							3	5
Total other comprehensive gain (loss), net of tax	(16)	(14)	(23)	21	(7)	(2)	(53)	12
Ending balance	1,829	$ 1,950	2,044	2,184	$ 2,234	2,294	1,829	2,184
Foreign Currency
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance			(65)			(28)	(65)	(28)
Other comprehensive income (loss) before reclassifications							10	(20)
Amounts reclassified from accumulated other comprehensive loss							0	0
Total other comprehensive gain (loss), net of tax							10	(20)
Ending balance	(55)			(48)			(55)	(48)
Effective Portion of Change in Fair Value of Derivatives
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance						(4)		(4)
Other comprehensive income (loss) before reclassifications								21
Amounts reclassified from accumulated other comprehensive loss								1
Total other comprehensive gain (loss), net of tax								22
Ending balance				18				18
Effective Portion of Change in Fair Value of Derivatives
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance			(4)				(4)
Other comprehensive income (loss) before reclassifications							(59)
Amounts reclassified from accumulated other comprehensive loss							2
Total other comprehensive gain (loss), net of tax							(57)
Ending balance	(61)						(61)
Proportionate Share of Equity Investee’s OCI
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance			9			7	9	7
Other comprehensive income (loss) before reclassifications							(7)	6
Amounts reclassified from accumulated other comprehensive loss							1	4
Total other comprehensive gain (loss), net of tax							(6)	10
Ending balance	3			17			3	17
AOCI
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance			$ (60)			$ (25)	(60)	(25)
Ending balance	$ (113)			$ (13)			$ (113)	$ (13)