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Derivative Financial Instruments and Hedging (Details2) - USD ($) $ in Millions | Mar. 31, 2018 | Dec. 31, 2017
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Derivatives Fair Value [Line Items] |  |
Derivative Fair Value Of Derivative Asset | $ 15.6 | $ 16.5
Derivative Fair Value Of Derivative Liability | 4.5 | 5.5
Designated as Hedging Instrument |  |
Derivatives Fair Value [Line Items] |  |
Derivative Fair Value Of Derivative Asset | 15.6 | 16.4
Derivative Fair Value Of Derivative Liability | 4.3 | 5.5
Designated as Hedging Instrument | Nickel and other raw material contracts | Prepaid expenses and other current assets |  |
Derivatives Fair Value [Line Items] |  |
Derivative Fair Value Of Derivative Asset | 10.2 | 10.5
Designated as Hedging Instrument | Nickel and other raw material contracts | Other assets |  |
Derivatives Fair Value [Line Items] |  |
Derivative Fair Value Of Derivative Asset | 5.1 | 5.5
Designated as Hedging Instrument | Nickel and other raw material contracts | Accrued liabilities |  |
Derivatives Fair Value [Line Items] |  |
Derivative Fair Value Of Derivative Liability | 1.5 | 2.1
Designated as Hedging Instrument | Nickel and other raw material contracts | Other long-term liabilities |  |
Derivatives Fair Value [Line Items] |  |
Derivative Fair Value Of Derivative Liability | 1.6 | 2.2
Designated as Hedging Instrument | Natural gas contracts | Prepaid expenses and other current assets |  |
Derivatives Fair Value [Line Items] |  |
Derivative Fair Value Of Derivative Asset | 0.2 | 0.1
Designated as Hedging Instrument | Natural gas contracts | Other assets |  |
Derivatives Fair Value [Line Items] |  |
Derivative Fair Value Of Derivative Asset | 0.1 | 0.3
Designated as Hedging Instrument | Natural gas contracts | Accrued liabilities |  |
Derivatives Fair Value [Line Items] |  |
Derivative Fair Value Of Derivative Liability | 0.2 | 0.9
Designated as Hedging Instrument | Natural gas contracts | Other long-term liabilities |  |
Derivatives Fair Value [Line Items] |  |
Derivative Fair Value Of Derivative Liability | 0.4 | 0.3
Designated as Hedging Instrument | Foreign exchange contracts | Accrued liabilities |  |
Derivatives Fair Value [Line Items] |  |
Derivative Fair Value Of Derivative Liability | 0.6 | 0.0
Not Designated as Hedging Instrument |  |
Derivatives Fair Value [Line Items] |  |
Derivative Fair Value Of Derivative Asset | 0.0 | 0.1
Derivative Fair Value Of Derivative Liability | 0.2 | 0.0
Not Designated as Hedging Instrument | Foreign exchange contracts | Prepaid expenses and other current assets |  |
Derivatives Fair Value [Line Items] |  |
Derivative Fair Value Of Derivative Asset | 0.0 | 0.1
Not Designated as Hedging Instrument | Foreign exchange contracts | Accrued liabilities |  |
Derivatives Fair Value [Line Items] |  |
Derivative Fair Value Of Derivative Liability | $ 0.2 | $ 0.0

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- Definition Fair value, before 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 elected not to be offset. Excludes assets not subject to a master netting arrangement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -Subparagraph (a),(c) -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624163-113959 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=82849420&loc=SL20226000-175313 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 20 -Section 50 -Paragraph 4D -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=82924980&loc=SL51823488-111719 + Details
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- Definition Fair value, before 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 elected not to be offset. Excludes liabilities not subject to a master netting arrangement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 20 -Section 50 -Paragraph 4D -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=82924980&loc=SL51823488-111719 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -Subparagraph (a),(c) -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624163-113959 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=82849420&loc=SL20226000-175313 + Details
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