Condensed Consolidated Statements of Operations (Parenthetical) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Costs and expenses:
Amortization of intangible assets	$ 9	$ 8	$ 23	$ 24
Depreciation	23	20	69	61
Amortization adjustment	18	16	54	50
Stock-based compensation:
Stock-based compensation	29	29	91	90
Cost of Revenue
Stock-based compensation:
Stock-based compensation			1
Selling and Marketing
Stock-based compensation:
Stock-based compensation	5	5	17	17
Technology and Content
Stock-based compensation:
Stock-based compensation	13	13	40	38
General and Administrative
Stock-based compensation:
Stock-based compensation	11	11	33	35
Acquired Technology
Costs and expenses:
Amortization of intangible assets	3	2	7	6
Website Development Costs
Costs and expenses:
Depreciation	$ 15	$ 14	$ 47	$ 44

The aggregate amount of recurring noncash expense charged against earnings in the period to allocate the cost of assets over their estimated remaining economic lives.

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