Segment Information - Revenue by Services and Geographic Area (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	$ 2,559	$ 3,276	$ 2,880	$ 2,508	$ 2,319	$ 2,966	$ 2,586	$ 2,189	$ 11,223	$ 10,060	$ 8,774
United States
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue									6,202	5,542	5,043
All other countries
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue									5,021	4,518	3,731
Lodging
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue									7,712	6,851	6,021
Air
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue									881	784	778
Advertising and media
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue									1,092	1,073	807
Other
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue									1,538	1,352	1,168
Sales Channel, Through Intermediary [Member] | Merchant
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue									5,950	5,394	4,853
Sales Channel, Through Intermediary [Member] | Agency
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue									3,010	2,687	2,425
Sales Channel, Through Intermediary [Member] | Advertising and media
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue									1,092	1,073	807
Sales Channel, Through Intermediary [Member] | HomeAway
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue									$ 1,171	$ 906	$ 689