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Derivatives Net Gain (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Derivative [Line Items]
Derivative, (loss) gain on derivative, net	$ 10.3	$ 0.8	$ 10.7	$ 2.8
Commodity Contract [Member]
Derivative [Line Items]
Derivative, (loss) gain on derivative, net	10.6	1.0	11.2	3.0
Commodity Contract [Member] | Glencore [Member]
Derivative [Line Items]
Derivative, (loss) gain on derivative, net	1.9	0.0	2.7	(0.1)
Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative, (loss) gain on derivative, net	$ (0.3)	$ (0.2)	$ (0.5)	$ (0.2)

X

- Definition

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5618551-113959

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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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