Goodwill and Other Intangible Assets - goodwill rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Goodwill, Beginning Balance	$ 57
Goodwill, Ending Balance	16,617	$ 57
Expedia
Goodwill [Line Items]
Acquisitions	16,796
Foreign exchange translation	(236)
Other
Goodwill, Ending Balance	16,560
Vitalize
Goodwill [Line Items]
Goodwill, Beginning Balance	57	57
Acquisitions
Foreign exchange translation
Other
Goodwill, Ending Balance	57	57
Corporate and Other
Goodwill [Line Items]
Goodwill, Beginning Balance	57	57
Acquisitions	16,796
Foreign exchange translation	(236)
Other
Goodwill, Ending Balance	$ 16,617	$ 57