Derivatives, Hedging Programs and Other Financial Instruments, Realized and Unrealized Gains (Losses) Table (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Derivative Instruments Gain Loss [Line Items]
Cost of products sold, excluding depreciation and amortization and other items	$ 315.1	$ 316.7
Cost of Sales
Derivative Instruments Gain Loss [Line Items]
Cost of products sold, excluding depreciation and amortization and other items		316.7
Cost of Sales \| Designated as Hedging Instrument
Derivative Instruments Gain Loss [Line Items]
Loss (gain) recognized in income related to cash flow hedges:	4.2	(0.1)
Cost of Sales \| Aluminum \| Designated as Hedging Instrument
Derivative Instruments Gain Loss [Line Items]
Loss (gain) recognized in income related to cash flow hedges:	4.2	0.3
Cost of Sales \| Alloy Metal Hedge \| Designated as Hedging Instrument
Derivative Instruments Gain Loss [Line Items]
Loss (gain) recognized in income related to cash flow hedges:	0.1	(0.4)
Cost of Sales \| Natural Gas \| Designated as Hedging Instrument
Derivative Instruments Gain Loss [Line Items]
Loss (gain) recognized in income related to cash flow hedges:	$ (0.1)	$ 0.0

The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
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-Paragraph 2
-Subparagraph (SX 210.5-03.2(a),(d))
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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
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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.

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