Consolidated Statements of Operations (Parenthetical) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Costs and expenses:
Amortization of intangible assets	$ 18		$ 6		$ 6
Depreciation	47	[1]	30	[1]	20	[1]
Amortization adjustment	34		21		14
Stock-based compensation:
Stock-based compensation	63		49		30
Acquired technology
Costs and expenses:
Amortization of intangible assets	4		1		1
Website development costs
Costs and expenses:
Depreciation	30		20		13
Selling and Marketing
Stock-based compensation:
Stock-based compensation	13		11		5
Technology and Content
Stock-based compensation:
Stock-based compensation	27		21		11
General and Administrative
Stock-based compensation:
Stock-based compensation	$ 23		$ 17		$ 14

[1] Includes amortization of internal use software and website development costs.