Acquisition and Disposition - Narrative (Details) - Teachers On Call, Inc. - USD ($) $ in Millions		3 Months Ended
Sep. 05, 2017	Apr. 01, 2018	Sep. 30, 2018
Business Acquisition [Line Items]
Ownership percentage acquired	100.00%
Purchase price of acquisition	$ 41.0
Purchase price paid at closing	39.0
Working capital adjustment		$ 0.2
Goodwill expected to be deductible			$ 18.8
Indemnification asset recognized at acquisition	$ 2.8
Indemnification assets			$ 0.1

Business Combination, Indemnification Assets, Amount

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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 increase (decrease) from adjustments after acquisition date under purchase accounting of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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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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