Stock Based Awards and Other Equity Instruments - Amount of Stock-Based Compensation Related to Stock-Based Awards, Primarily Stock Options and RSUs (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 63	$ 49	$ 30
Income tax benefit from stock-based compensation	(24)	(18)	(10)
Total stock-based compensation, net of tax effect	39	31	20
Selling and Marketing
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	13	11	5
Technology and Content
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	27	21	11
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 23	$ 17	$ 14