GOODWILL, INTANGIBLE ASSETS AND OTHER LONG-LIVED ASSETS - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Sep. 30, 2020	Mar. 31, 2020	Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Goodwill [Line Items]
Impairment of goodwill			$ 1,062		$ 0		$ 0
Goodwill			1,895	[1]	2,913	[1]	2,910
Intangible assets amortization expense			167		175		$ 178
OpenTable and KAYAK
Goodwill [Line Items]
Impairment of goodwill	$ 573	$ 489	$ 1,062		$ 0
Goodwill	1,000	$ 1,500
Potential increase in fair value from 1% point increase in profitability growth rate	100
Potential decrease in fair value from 1% point decrease in profitability growth rate	100
Potential decrease in fair value due to 0.5% increase in discount rate	65
Potential increase in fair value due to 0.5% decrease in discount rate	$ 70
Sensitivity Analysis, Reporting Unit, Change in Growth Rate	1.00%
Sensitivity Analysis, Reporting Unit, Change in Discount Rate	0.50%

[1] The balance of goodwill as of December 31, 2020 and 2019 is stated net of cumulative impairment charges of $2.0 billion and $941 million, respectively.