Fair Value Measurements (Details 2) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Business Acquisition, Contingent Consideration [Line Items]
Changes in fair value	$ 1.9	$ 21.2	$ (3.7)	$ 31.2
Payments	0.0	0.0	(20.0)	(6.7)
Fair Value, Measurements, Recurring
Business Acquisition, Contingent Consideration [Line Items]
Fair value, beginning of period	498.0	470.9	523.6	467.6
Fair value, end of period	$ 499.9	$ 492.1	$ 499.9	$ 492.1

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.

No definition available.

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Amount of liability recognized arising from contingent consideration in a business combination.

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Amount of gain (loss) recognized on the income statement for financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of settlements of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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