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Amount of consideration received or receivable for the disposal of assets and liabilities, including discontinued operation.

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Amount of operating income (loss) attributable to disposal group, including, but not limited to, discontinued operation.

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Amount of revenue attributable to disposal group, including, but not limited to, discontinued operation.

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Amount of gain (loss) on sale or disposal of assets, including but not limited to property plant and equipment, intangible assets and equity in securities of subsidiaries or equity method investee.

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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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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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The cash inflow associated with the amount received from the sale of a portion of the company's business, for example a segment, division, branch or other business, during the period.

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The cash inflow from the sale of property, plant and equipment (capital expenditures), software, and other intangible assets.

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Acquisitions and Divestitures - Divestitures (Details) $ in Thousands				12 Months Ended
	Aug. 31, 2018 USD ($)	May 01, 2018 USD ($)	Apr. 03, 2018 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on disposal				$ 0	$ (2,075)	$ 45,447
Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of businesses sold \| business						3
Divestiture, revenue contributed						$ 97,300
Divestiture, gross contribution						60,500
Disposed of by Sale \| CEB Challenger
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale of business, consideration	$ 119,100
Proceeds from divestiture of businesses	116,000
Gain on disposal	$ 8,300
Disposed of by Sale \| CEB Workforce Survey and Analytics
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale of business, consideration		$ 28,000
Proceeds from divestiture of businesses		26,400
Gain on disposal		$ 8,800
Disposed of by Sale \| CEB Talent Assessment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale of business, consideration			$ 403,000
Proceeds from divestiture of businesses			375,800
Gain on disposal			$ 15,500
Disposed of by Sale \| Other Certain Assets In CEB Transaction
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of assets						8,600
Gain on sale of assets						$ 12,800