Derivative Instruments (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Derivative Instruments
Maximum Remaining Maturity of Foreign Currency Derivatives	6 months
Notes Payable 4.5 Percent Due 2021 [Member]
Derivative Instruments
Debt instrument, face amount	$ 400.0
Fixed-rate (as a percent)	4.50%
Derivatives not designated as hedging instruments \| Forward exchange contracts
Derivative Instruments
Notional amounts of derivatives	$ 0.3	$ 2.7
Derivatives designated as hedging instruments \| Interest-rate swap
Derivative Instruments
Notional amounts of derivatives	$ 400.0
Number of swap agreements	4
(Level 2) \| Measured on a recurring basis \| Interest-rate swap
Derivative Instruments
Derivative Liability	$ 2.7	0.6
Derivative Asset	$ 0.0	$ 0.0

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

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
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- Definition

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

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- Definition

Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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- Definition

The number of derivative instruments of a particular group held by the entity.

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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

Maximum amount of time remaining before foreign currency exchange rate derivatives mature or expire, 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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