INTANGIBLE ASSETS AND GOODWILL (Details) - USD ($)			3 Months Ended		9 Months Ended
	Nov. 30, 2018	Apr. 26, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Finite-lived intangible assets
Gross Carrying Amount			$ 3,102,000,000		$ 3,102,000,000		$ 3,126,000,000
Accumulated Amortization			(1,117,000,000)		(1,117,000,000)		(1,001,000,000)
Net Carrying Amount			1,985,000,000		1,985,000,000		2,125,000,000
Amortization expense			43,000,000	$ 43,000,000	132,000,000	$ 135,000,000
Impairment of goodwill					0
Acquisitions and other investments, net of cash acquired					9,000,000	139,000,000
Common stock issued in an acquisition						110,000,000
Non-cash operating and financing activity for an acquisition					0	51,000,000
Non-cash investing and financing activity for an acquisition					0	59,000,000
Supply and distribution agreements
Finite-lived intangible assets
Gross Carrying Amount			1,083,000,000		1,083,000,000		1,099,000,000
Accumulated Amortization			(446,000,000)		(446,000,000)		(408,000,000)
Net Carrying Amount			637,000,000		637,000,000		691,000,000
Technology
Finite-lived intangible assets
Gross Carrying Amount			174,000,000		174,000,000		173,000,000
Accumulated Amortization			(131,000,000)		(131,000,000)		(121,000,000)
Net Carrying Amount			43,000,000		43,000,000		52,000,000
Internet domain names
Finite-lived intangible assets
Gross Carrying Amount			39,000,000		39,000,000		41,000,000
Accumulated Amortization			(30,000,000)		(30,000,000)		(30,000,000)
Net Carrying Amount			9,000,000		9,000,000		11,000,000
Trade Names
Finite-lived intangible assets
Gross Carrying Amount			1,804,000,000		1,804,000,000		1,810,000,000
Accumulated Amortization			(508,000,000)		(508,000,000)		(439,000,000)
Net Carrying Amount			1,296,000,000		1,296,000,000		1,371,000,000
Other Intangible Assets
Finite-lived intangible assets
Gross Carrying Amount			2,000,000		2,000,000		3,000,000
Accumulated Amortization			(2,000,000)		(2,000,000)		(3,000,000)
Net Carrying Amount			$ 0		$ 0		$ 0
Minimum | Supply and distribution agreements
Finite-lived intangible assets
Amortization Period					3 years
Minimum | Technology
Finite-lived intangible assets
Amortization Period					1 year
Minimum | Internet domain names
Finite-lived intangible assets
Amortization Period					5 years
Minimum | Trade Names
Finite-lived intangible assets
Amortization Period					4 years
Minimum | Other Intangible Assets
Finite-lived intangible assets
Amortization Period					0 years
Maximum | Supply and distribution agreements
Finite-lived intangible assets
Amortization Period					20 years
Maximum | Technology
Finite-lived intangible assets
Amortization Period					7 years
Maximum | Internet domain names
Finite-lived intangible assets
Amortization Period					20 years
Maximum | Trade Names
Finite-lived intangible assets
Amortization Period					20 years
Maximum | Other Intangible Assets
Finite-lived intangible assets
Amortization Period					15 years
HotelsCombined
Finite-lived intangible assets
Acquisitions and other investments, net of cash acquired	$ 134,000,000
FareHarbor
Finite-lived intangible assets
Acquisitions and other investments, net of cash acquired		$ 139,000,000
Common stock issued in an acquisition		$ 110,000,000
Non-cash operating and financing activity for an acquisition						59,000,000
Non-cash investing and financing activity for an acquisition						$ 51,000,000