The amount of cash investment.

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Represents the percentage of transfer of ownership.

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The number of shares in exchange for concurrent cash investment.

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Period for useful life of assets acquired, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Number of shares of equity interests issued or issuable to acquire entity.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Percentage of voting equity interests acquired at the acquisition date in the business combination.

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Price of a single share of a number of saleable stocks paid or offered to be paid in a business combination.

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No definition available.

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Amount of gain (loss) from sale and disposal of integrated set of activities and assets capable of being conducted and managed for purpose of providing return in form of dividend, lower cost, or other economic benefit to investor, owner, member and participant.

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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Number of shares of stock issued during the period pursuant to acquisitions.

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Acquisition and Disposition - Additional information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Aug. 31, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Feb. 28, 2021	Feb. 16, 2021
Business Acquisition [Line Items]
Revenue		$ 90,096	$ 75,243	$ 251,848	$ 198,297	$ 321,324	$ 317,923	$ 307,251
Goodwill		5,927		$ 5,927
Trade names
Business Acquisition [Line Items]
Useful lives of assets acquired				3 years
Trade marks
Business Acquisition [Line Items]
Useful lives of assets acquired				15 years
HuffPost Acquisition
Business Acquisition [Line Items]
Percentage of interest acquired										100.00%
Number of shares issued				8,625,234
HuffPost Acquisition (in shares)				8,625,234
Shares Issued in Exchange for Concurrent Cash Investment				12,544,803
Cash investment		$ 35,000		$ 35,000
Business acquisition price		$ 2.79		$ 2.79
Revenue		$ 9,200		$ 19,100
Ownership interest	51.00%
Loss of disposition	$ 600
Goodwill		$ 5,927		$ 5,927		$ 0
Verizon
Business Acquisition [Line Items]
Number of shares issued				21,170,037
Cash investment									$ 35,000