COMMITMENTS AND CONTINGENCIES - Building Construction (Details) € in Millions, $ in Millions	1 Months Ended
	Sep. 30, 2016 USD ($)	Sep. 30, 2016 EUR (€)	Dec. 31, 2021 USD ($)	Dec. 31, 2021 EUR (€)	Sep. 30, 2016 EUR (€)
Other Commitments [Line Items]
Remaining lease obligations			$ 550
Booking.com | Headquarters
Other Commitments [Line Items]
Contractual obligation	$ 307		17	€ 15	€ 270
Acquisition of land use rights	$ 48	€ 43
Booking.com | Headquarters | Vendors used to fit out and furnish office space
Other Commitments [Line Items]
Contractual obligation			23	20
Booking.com | Headquarters | Ground Lease
Other Commitments [Line Items]
Remaining lease obligations			$ 77	€ 68