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Number Of Businesses Sold

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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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Amount before tax of income (loss) from a discontinued operation. Includes, but is not limited to, the income (loss) from operations during the phase-out period, gain (loss) on disposal, gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and adjustments to a prior period gain (loss) on disposal.

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

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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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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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Acquisitions and Divestitures (Details) $ in Thousands			3 Months Ended		6 Months Ended
Acquisitions and Divestitures (Details) $ in Thousands	May 01, 2018 USD ($)	Apr. 03, 2018 USD ($)	Jun. 30, 2018 USD ($) business	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)
Business Acquisition [Line Items]
Acquisition and integration charges			$ 19,962	$ 98,332	$ 79,228	$ 111,604
Number of businesses sold \| business			2
Divestitures - cash received (net of cash transferred)					405,542	0
Gain from divested operations			$ 25,460	0	25,460	0
Gain from divested operations			25,460	$ 0	25,460	$ 0
Talent Assessment \| Disposal Group, Held-for-sale, Not Discontinued Operations
Business Acquisition [Line Items]
Disposal consideration		$ 403,000
Divestitures - cash received (net of cash transferred)		377,800
Gain from divested operations		$ 16,000
Disposal group, revenue					47,000
Gain from divested operations					$ 2,100
CEB Workforce Survey and Analytics \| Disposal Group, Held-for-sale, Not Discontinued Operations
Business Acquisition [Line Items]
Disposal consideration	$ 28,000
Divestitures - cash received (net of cash transferred)	26,400		1,300
Gain from divested operations	$ 8,800		$ 700