Segment Information - Revenue by Business Model and Service Type (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Revenue	$ 3,558	$ 3,276	$ 9,320	$ 8,664
Lodging
Segment Reporting Information [Line Items]
Revenue	2,599	2,347	6,555	5,951
Air
Segment Reporting Information [Line Items]
Revenue	202	209	678	674
Advertising and media
Segment Reporting Information [Line Items]
Revenue	311	302	860	858
Other
Segment Reporting Information [Line Items]
Revenue	446	418	1,227	1,181
Sales Channel, Through Intermediary | Merchant
Segment Reporting Information [Line Items]
Revenue	1,863	1,688	4,935	4,554
Sales Channel, Through Intermediary | Agency
Segment Reporting Information [Line Items]
Revenue	917	876	2,444	2,311
Sales Channel, Through Intermediary | Advertising and media
Segment Reporting Information [Line Items]
Revenue	311	302	860	858
Sales Channel, Through Intermediary | Vrbo
Segment Reporting Information [Line Items]
Revenue	$ 467	$ 410	$ 1,081	$ 941