Segment Information - Revenue by Business Model and Service Type (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Revenue	$ 566	$ 3,153	$ 2,775	$ 5,762
Lodging
Segment Reporting Information [Line Items]
Revenue	487	2,204	2,029	3,893
Air
Segment Reporting Information [Line Items]
Revenue	(70)	228	39	476
Advertising and media
Segment Reporting Information [Line Items]
Revenue	25	284	228	549
Other
Segment Reporting Information [Line Items]
Revenue	124	437	479	844
Sales Channel, Through Intermediary | Merchant
Segment Reporting Information [Line Items]
Revenue	368	1,758	1,708	3,193
Sales Channel, Through Intermediary | Agency
Segment Reporting Information [Line Items]
Revenue	105	1,047	667	1,889
Sales Channel, Through Intermediary | Advertising, media and other
Segment Reporting Information [Line Items]
Revenue	$ 93	$ 348	$ 400	$ 680