INTANGIBLE ASSETS AND GOODWILL (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
	Nov. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Finite-lived intangible assets
Gross Carrying Amount		$ 3,129		$ 3,129		$ 3,126
Accumulated Amortization		(1,088)		(1,088)		(1,001)
Net Carrying Amount		2,041		2,041		2,125
Amortization expense		44	$ 45	89	$ 92
Acquisitions and other investments, net of cash acquired				9	139
Common stock issued in an acquisition			$ 110		110
Non-cash operating and financing activity for an acquisition				0	51
Non-cash investing and financing activity for an acquisition				0	59
Supply and distribution agreements
Finite-lived intangible assets
Gross Carrying Amount		1,100		1,100		1,099
Accumulated Amortization		(440)		(440)		(408)
Net Carrying Amount		660		660		691
Technology
Finite-lived intangible assets
Gross Carrying Amount		176		176		173
Accumulated Amortization		(129)		(129)		(121)
Net Carrying Amount		47		47		52
Internet domain names
Finite-lived intangible assets
Gross Carrying Amount		41		41		41
Accumulated Amortization		(31)		(31)		(30)
Net Carrying Amount		10		10		11
Trade Names
Finite-lived intangible assets
Gross Carrying Amount		1,810		1,810		1,810
Accumulated Amortization		(486)		(486)		(439)
Net Carrying Amount		1,324		1,324		1,371
Other Intangible Assets
Finite-lived intangible assets
Gross Carrying Amount		2		2		3
Accumulated Amortization		(2)		(2)		(3)
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
FareHarbor
Finite-lived intangible assets
Acquisitions and other investments, net of cash acquired					139
Common stock issued in an acquisition					110
Non-cash operating and financing activity for an acquisition					59
Non-cash investing and financing activity for an acquisition					$ 51