Business Combination, Acquisition and Integration Related Costs

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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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No definition available.

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

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Acquisitions and Divestitures (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Apr. 30, 2018	Apr. 03, 2018
Business Acquisition [Line Items]
Acquisition and integration charges	$ 59,266	$ 13,272
Talent Assessment \| Disposal Group, Held-for-sale, Not Discontinued Operations
Business Acquisition [Line Items]
Disposal group, revenue	47,000
Disposal group, pre-tax income	$ 2,100
Subsequent Event \| Talent Assessment \| Disposal Group, Held-for-sale, Not Discontinued Operations
Business Acquisition [Line Items]
Disposal group, consideration received				$ 400,000
Subsequent Event \| Workforce Surveys & Analytics \| Disposal Group, Held-for-sale, Not Discontinued Operations
Business Acquisition [Line Items]
Disposal group, consideration received			$ 29,000