Acquisition - Narrative (Details) - Teachers On Call, Inc. $ in Millions	Sep. 05, 2017 USD ($) Rate
Business Acquisition [Line Items]
Ownership percentage acquired \| Rate	100.00%
Purchase price of acquisition	$ 41.0
Purchase price paid at closing	39.0
Intangible assets acquired	18.3
Goodwill expected to be deductible	18.3
Indemnification asset recognized	2.8
Trademarks
Business Acquisition [Line Items]
Indefinite-lived intangibles	4.8
Customer relationships
Business Acquisition [Line Items]
Finite-lived intangibles	$ 12.0
Useful life of intangible assets acquired	10 years
Candidate database
Business Acquisition [Line Items]
Finite-lived intangibles	$ 1.5
Useful life of intangible assets acquired	4 years

Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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

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The amount of goodwill arising from a business combination that is expected to be deductible for tax purposes.

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Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

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The amount of indemnification assets (amounts to be reimbursed if and when certain assumed liabilities are paid) recognized at the acquisition date of a business combination.

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Amount of assets, excluding financial assets and goodwill, that lack physical substance, having a projected indefinite period of benefit, acquired at the acquisition date.

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Amount of intangible assets, excluding goodwill, acquired at the acquisition date.

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The amount of identifiable intangible assets recognized as of the acquisition date.

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The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

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