Consolidated Statements of Operations (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Costs and expenses:
Amortization of intangible assets	$ 26	$ 33	$ 34
Amortization adjustment	70	73	67
Stock-based compensation:
Stock-based compensation	109	124	118
Cost of Revenue
Stock-based compensation:
Stock-based compensation	1	1	1
Selling and Marketing
Stock-based compensation:
Stock-based compensation	16	23	21
Technology and Content
Stock-based compensation:
Stock-based compensation	44	55	51
General and Administrative
Stock-based compensation:
Stock-based compensation	48	45	45
Acquired Technology
Costs and expenses:
Amortization of intangible assets	3	10	8
Website Development Costs
Costs and expenses:
Depreciation	$ 67	$ 63	$ 59