Goodwill and Intangible Assets, Net - Changes in Goodwill by Reportable Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Goodwill, Beginning Balance	$ 8,229	$ 7,942
Additions	31	124
Impairment of goodwill	(86)	0	$ 0
Foreign exchange translation and other		163
Foreign exchange translation and other	(54)
Goodwill, Ending Balance	8,120	8,229	7,942
Core OTA
Goodwill [Line Items]
Goodwill, Beginning Balance	4,840	4,703
Additions	0	124
Impairment of goodwill	(86)
Foreign exchange translation and other		13
Foreign exchange translation and other	(13)
Goodwill, Ending Balance	4,741	4,840	4,703
trivago
Goodwill [Line Items]
Goodwill, Beginning Balance	588	516
Additions	0	0
Impairment of goodwill	0
Foreign exchange translation and other		72
Foreign exchange translation and other	(27)
Goodwill, Ending Balance	561	588	516
HomeAway
Goodwill [Line Items]
Goodwill, Beginning Balance	2,656	2,591
Additions	31
Impairment of goodwill	0
Foreign exchange translation and other		65
Foreign exchange translation and other	(5)
Goodwill, Ending Balance	2,682	2,656	2,591
Egencia
Goodwill [Line Items]
Goodwill, Beginning Balance	145	132
Additions	0
Impairment of goodwill	0
Foreign exchange translation and other		13
Foreign exchange translation and other	(9)
Goodwill, Ending Balance	$ 136	$ 145	$ 132