REVENUE - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue [Line Items]
Revenues	$ 1,141	$ 2,288
Online accommodation reservation services | Revenue Benchmark | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration risk percentage	86.00%	85.00%
Other sources of online travel reservation services and advertising and other revenues | Revenue Benchmark | Product Concentration Risk | Maximum
Disaggregation of Revenue [Line Items]
Concentration risk percentage	10.00%	10.00%
United States
Disaggregation of Revenue [Line Items]
Revenues	$ 197	$ 285
The Netherlands
Disaggregation of Revenue [Line Items]
Revenues	811	1,677
Other
Disaggregation of Revenue [Line Items]
Revenues	$ 133	$ 326