Hedging - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative term	1 month
Foreign currency forward contracts \| Not designated as hedging instrument
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount of foreign currency forward contract	$ 122.8
Derivative term	1 month
Other nonoperating income (expense) \| Foreign currency forward contracts \| Not designated as hedging instrument
Derivative Instruments and Hedging Activities Disclosures [Line Items]
(Loss) gain recognized on forward contracts not designated as hedges	$ (14.1)	$ 6.9

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

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+ References

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- Definition

Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

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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

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