Intangible Assets (Changes In Carrying Amount Of Goodwill By Segment) (Details) (USD $) In Millions	9 Months Ended
	Sep. 30, 2011
Balance at December 31, 2010	$ 1,481
Goodwill Acquired	10
Foreign exchange	(8)
Balance at September 30, 2011	1,483
Lodging [Member]
Balance at December 31, 2010	300
Goodwill Acquired
Foreign exchange
Balance at September 30, 2011	300
Vacation Exchange and Rentals [Member]
Balance at December 31, 2010	1,181
Goodwill Acquired	10	[1]
Foreign exchange	(8)
Balance at September 30, 2011	$ 1,183

[1] Relates to two tuck-in acquisitions completed during the third quarter of 2011 (see Note 3—Acquisitions).