Condensed Consolidated Statements of Operations (Parenthetical) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Costs and expenses:
Amortization of intangible assets	$ 7	$ 8	$ 15	$ 16
Depreciation	23	21	46	41
Amortization adjustment	17	17	36	34
Stock-based compensation:
Stock-based compensation	32	31	60	61
Selling and Marketing
Stock-based compensation:
Stock-based compensation	6	5	11	11
Technology and Content
Stock-based compensation:
Stock-based compensation	14	13	27	26
General and Administrative
Stock-based compensation:
Stock-based compensation	12	13	22	24
Acquired Technology
Costs and expenses:
Amortization of intangible assets	2	2	4	4
Website Development Costs
Costs and expenses:
Depreciation	$ 15	$ 15	$ 32	$ 30

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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