Segment and Geographic Information - Summary of Segment Information (Parenthetical) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Segment Reporting Information [Line Items]
General and administrative expenses	$ 128	[1]	$ 98	[1]	$ 76	[1]
Hotel
Segment Reporting Information [Line Items]
General and administrative expenses	87		72		56
Other Segment
Segment Reporting Information [Line Items]
General and administrative expenses	$ 18		$ 9		$ 6

[1] Includes stock-based compensation expense as follows: