Derivative Financial Instruments and Related Hedging Programs, Notional Quantity Table (Details) - Jun. 30, 2015	EUR (€) mmlbs MMBTU MWH
Remainder of 2015
Summary of material derivative positions
Percentage of natural gas purchases for which the Company's exposure to fluctuations in gas prices had been substantially reduced	79.00%
Percentage of Electricity Purchases For Which Company Exposure To Fluctuations In Electricity Prices Have Been Reduced	54.00%
2016
Summary of material derivative positions
Percentage of natural gas purchases for which the Company's exposure to fluctuations in gas prices had been substantially reduced	75.00%
Percentage of Electricity Purchases For Which Company Exposure To Fluctuations In Electricity Prices Have Been Reduced	54.00%
2017
Summary of material derivative positions
Percentage of natural gas purchases for which the Company's exposure to fluctuations in gas prices had been substantially reduced	34.00%
Percentage of Electricity Purchases For Which Company Exposure To Fluctuations In Electricity Prices Have Been Reduced	36.00%
Not Designated as Hedging Instrument \| Electricity Member \| Fixed priced contracts \| Purchase
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount \| MWH	88,340
Not Designated as Hedging Instrument \| Aluminum \| Fixed priced contracts \| Purchase
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	117.1
Not Designated as Hedging Instrument \| Aluminum \| Fixed priced contracts \| Sales
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	0.9
Not Designated as Hedging Instrument \| Aluminum \| Midwest premium swap contracts \| Purchase
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	93.2
Not Designated as Hedging Instrument \| Natural Gas \| Fixed priced contracts \| Purchase
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount \| MMBTU	6,160,000
Designated as Hedging Instrument [Member] \| Foreign Currency Member \| Fixed priced contracts \| Purchase
Summary of material derivative positions
Notional amount of contracts \| €	€ 8,135,000

Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract.

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

-Publisher SEC

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-Number 210

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+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1B

-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5580258-113959

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