Condensed Consolidated Statements of Operations (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Costs and expenses:
Amortization of intangible assets	$ 8	$ 10	$ 23	$ 26
Depreciation	18	13	51	42
Amortization adjustment	14	10	38	34
Stock-based compensation:
Stock-based compensation	22	19	64	52
Selling and Marketing
Stock-based compensation:
Stock-based compensation	5	4	15	12
Technology and Content
Stock-based compensation:
Stock-based compensation	11	8	30	20
General and Administrative
Stock-based compensation:
Stock-based compensation	6	7	19	20
Acquired Technology
Costs and expenses:
Amortization of intangible assets	2	2	5	7
Website Development Costs
Costs and expenses:
Depreciation	$ 12	$ 8	$ 33	$ 27