Accumulated Other Comprehensive Income (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		$ 6,500	$ 5,345	$ 5,538	$ 3,904	[1]	$ 3,583	[1]	$ 2,224	[1]	$ 5,538	$ 2,224	[1]
Total other comprehensive income (loss), net of tax		0	0	(5)	8	[1],[2]	(5)	[1]	1	[1]	(5)	4	[2]
Impact of disposal of Canadian Holdings	[1]						107
Ending balance		6,176	6,500	5,345	4,046	[1]	3,904	[1]	3,583	[1]	6,176	4,046	[1]
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance		(23)	(23)	(18)	(24)		(126)		(127)		(18)	(127)
Ending balance		(23)	(23)	(23)	(16)		(24)		(126)		(23)	(16)
Net Unrealized Gains (Losses) on Cash Flow Hedges [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance		0	0	6	6		2		1		6	1
Amounts reclassified from AOCI to interest expense				(6)	(1)		1		1
Total other comprehensive income (loss), net of tax		0	0	(6)	(1)		1		1
Impact of disposal of Canadian Holdings	[1]						3
Ending balance		0	0	0	5		6		2		0	5
Net Unrealized Gains (Losses) on Foreign Currency Translation [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance					0		(102)		(98)			(98)
Other comprehensive income (loss)							(2)		(4)
Total other comprehensive income (loss), net of tax					0		(2)		(4)
Impact of disposal of Canadian Holdings	[1]						104
Ending balance					0		0		(102)			0
Other Comprehensive Income (Loss) Related to Equity Method Investee [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance		(23)	(23)	(24)	(30)		(26)		(30)		(24)	(30)
Other comprehensive income (loss)				1	9		(4)		4
Total other comprehensive income (loss), net of tax		0	0	1	9		(4)		4
Impact of disposal of Canadian Holdings	[1]						0
Ending balance		(23)	$ (23)	$ (23)	(21)		$ (30)		$ (26)		(23)	(21)
Total Attributable to Noncontrolling Interest [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Ending balance		(15)			(11)						(15)	(11)
Net Unrealized Gains (Losses) on Cash Flow Hedges Attributable to Noncontrolling Interest [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Ending balance		0			4						0	4
Net Unrealized Gains (Losses) on Foreign Currency Translation Attributable to Noncontrolling Interest [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Ending balance					0							0
Other Comprehensive Income (Loss) Related to Equity Method Investee Attributable to Noncontrolling Interest [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Ending balance		(15)			(15)						(15)	(15)
Total Attributable to Parent [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Ending balance		(8)			(5)						(8)	(5)
Net Unrealized Gains (Losses) on Cash Flow Hedges Attributable to Parent [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Ending balance		0			1						0	1
Net Unrealized Gains (Losses) on Foreign Currency Translation Attributable to Parent [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Ending balance					0							0
Other Comprehensive Income (Loss) Related to Equity Method Investee Attributable to Parent [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Ending balance		$ (8)			$ (6)						$ (8)	$ (6)

[1] Prior-period financial information has been retrospectively adjusted to include the adoption of an accounting standards update related to leases.

[2] Prior-period financial information has been retrospectively adjusted to include the adoption of an accounting standards update related to leases.