Financial Instruments (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2018	Dec. 31, 2017
Cash
Derivative Financial Instruments
Deferred compensation, Rabbi Trust	$ 10.7	$ 13.2
Short-term Investments
Derivative Financial Instruments
Deferred compensation, Rabbi Trust	5.3	4.0
Designated as Hedging Instrument
Derivative Financial Instruments
Fair value		(0.2)
Foreign Exchange Forward \| Designated as Hedging Instrument
Derivative Financial Instruments
Fair value	0.0
Notional amount	6.2	22.3
Foreign Exchange Forward \| Not Designated as Hedging Instrument
Derivative Financial Instruments
Fair value	(0.1)	0.2
Notional amount	$ 38.4	$ 38.6
Maximum \| Foreign Exchange Forward \| Not Designated as Hedging Instrument
Derivative Financial Instruments
Maturity term	1 year
Maximum \| Cash Flow Hedging \| Foreign Exchange Forward \| Designated as Hedging Instrument
Derivative Financial Instruments
Maturity term	1 year

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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- Definition

Aggregate carrying value as of the balance sheet date of the liabilities for deferred compensation arrangements. Represents currently earned compensation under cash arrangements (such as a profit-sharing plan, rabbi trust, and employee contract--excluding equity-based arrangements) that is not actually paid until a later date.

+ References

No definition available.

+ Details

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- Definition

Fair value of the assets less the liabilities of a derivative or group of derivatives.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13433-108611

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- Definition

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.

+ References

No definition available.

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- Definition

Period the derivative contract is outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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