REVENUE - Refunds to Travelers (Details) $ in Millions	12 Months Ended
Dec. 31, 2020 USD ($)
Revenue from Contract with Customer [Abstract]
Reduction in revenue for refunds paid or estimated to be payable	$ 44

Amount of reduction to revenue for refunds paid or estimated to be payable to travelers to provide free cancellation for certain non-refundable reservations without a corresponding estimated expected recovery from the travel service provider.

No definition available.

Name:	bkng_ContractWithCustomerReductionToRevenueForRefundsPaidOrEstimatedToBePayableToTravelers
Namespace Prefix:	bkng_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration