Derivative And Other Financial Instruments (Schedule of Realized (Gains) Losses on Derivatives) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Metal
Derivative Instruments, Loss [Line Items]
Realized losses on derivative financial instruments	$ 1.0	$ 19.5
Energy Related Derivative
Derivative Instruments, Loss [Line Items]
Realized losses on derivative financial instruments	(0.2)	0.4
Currency
Derivative Instruments, Loss [Line Items]
Realized losses on derivative financial instruments	$ (1.0)	$ 0.5

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5618551-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (a),(c),(d),(e)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration