Derivative Instruments and Hedging Activities (Details 3) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) arising in period	$ (1.4)	$ (8.0)
Reclassification of losses (gains) to net income (loss)	(7.6)	(0.6)
Other Nonoperating Income (Expense) [Member] \| Foreign Exchange Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives not designated as cash flow hedges:	(0.3)	(0.1)
Cost of Products Sold [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Reclassification of losses (gains) to net income (loss)	(7.6)	(0.6)
Cost of Products Sold [Member] \| Commodity Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives not designated as cash flow hedges:	(8.7)	15.3
Cash Flow Hedging [Member] \| Commodity Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) arising in period	0.3	(8.0)
Cash Flow Hedging [Member] \| Foreign Exchange Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) arising in period	(1.7)	0.0
Iron Ore [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives not designated as cash flow hedges:	(7.7)	16.3
Derivative, Cash Received on Hedge	$ 2.3	$ 11.4

The amount of cash received during the period on settlement of a hedge.

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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

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

Amount before tax of reclassification adjustment from accumulated other comprehensive income of accumulated gain (loss) realized from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's deferred hedging gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph c
-URI http://asc.fasb.org/extlink&oid=84234895&loc=d3e41638-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e689-108580

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e637-108580

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- Definition

Amount before tax of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6441202&loc=d3e80720-113993

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669646-108580

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e637-108580

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