Business Combinations (Details) $ in Millions	9 Months Ended
Sep. 30, 2018 USD ($) acquisition	Sep. 30, 2017 USD ($)
Business Acquisition [Line Items]
Number of Businesses Acquired \| acquisition	4
Payments to Acquire Businesses	$ 31.7
Business Combinations, Guaranteed Deferred Acquisition Obligation	1.9	$ 1.8
Business Combination, contingent earn-out consideration	2.7	$ 11.5
Goodwill, Acquired During Period	30.1
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	5.7
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	0.5
Payment for Contingent Consideration Liability, Total	63.3
Payments for Repurchase of Redeemable Noncontrolling Interest	$ 1.5

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Payment for Contingent Consideration Liability, Total

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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 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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Amount recognized as of the acquisition date for the identifiable assets acquired in excess of (less than) the aggregate liabilities assumed.

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Amount of increase in assets, excluding financial assets, lacking physical substance with a definite life, from an acquisition.

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Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

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The number of businesses acquired by the entity during the period.

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The cash outflow during the period for redemption of redeemable noncontrolling interests.

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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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