Derivative Instruments and Hedging Activities (Details 2) - USD ($) $ in Millions	3 Months Ended
Sep. 30, 2016	Dec. 31, 2015
Designated as Hedging Instrument [Member] \| Commodity Contract [Member] \| Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Current	$ 4.4	$ 0.3
Designated as Hedging Instrument [Member] \| Commodity Contract [Member] \| Other Non-current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Noncurrent	2.2	0.3
Designated as Hedging Instrument [Member] \| Commodity Contract [Member] \| Accrued Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Current	(5.5)	(40.9)
Designated as Hedging Instrument [Member] \| Commodity Contract [Member] \| Other Non-current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Noncurrent	(2.2)	(9.5)
Not Designated as Hedging Instrument [Member] \| Foreign Exchange Contract [Member] \| Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Current	0.0	1.1
Not Designated as Hedging Instrument [Member] \| Commodity Contract [Member] \| Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Current	6.2	0.2
Not Designated as Hedging Instrument [Member] \| Commodity Contract [Member] \| Other Non-current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Noncurrent	1.6	0.0
Not Designated as Hedging Instrument [Member] \| Commodity Contract [Member] \| Accrued Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Current	(0.9)	(0.3)
Not Designated as Hedging Instrument [Member] \| Commodity Contract [Member] \| Other Non-current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Noncurrent	(0.1)	$ 0.0
Reclassification out of Accumulated Other Comprehensive Income [Member] \| Iron Ore [Member] \| Commodity Contract [Member]
Derivatives, Fair Value [Line Items]
Gain on Discontinuation of Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring	$ 1.7

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, expected to be settled within one year or normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13495-108611

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Current Assets
-URI http://asc.fasb.org/extlink&oid=6509628

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Name Accounting Standards Codification
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-Publisher FASB
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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, expected to be settled after one year or the normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
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-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958

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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, expected to be settled within one year or normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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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, expected to be settled after one year or the normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 210
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- Definition

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+ References

No definition available.

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- Definition

The amount of gain reclassified into earnings in the period when cash flow hedge is discontinued because it is probable that the original forecasted transactions will not occur by the end of the original period or an additional two month time period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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