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Derivative Financial Instruments (Narrative) (Details) $ in Thousands, lb in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2017 USD ($) lb	Dec. 31, 2016 USD ($) lb
Derivative [Line Items]
Amounts of unrealized after tax gains (losses) to be Reclassified within Twelve Months	$ (600)
Aluminum Futures Contracts
Derivative [Line Items]
Notional Amount	$ 8,100	$ 8,000
Weight of aluminum that hedged future purchase of aluminum to meet fixed - price forward sales contract obligations, lbs | lb	9.3	9.6
Net asset (liability), Fair Value	$ 884	$ 271
Accrued Expenses [Member] | Derivatives Designated As Hedging Instruments [Member] | Aluminum Futures Contracts
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	896	308
Derivative Liability, Fair Value, Gross Liability	$ 12	$ 37

X

- Definition

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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- Definition

The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=35736893&loc=d3e80748-113994

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Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

+ References

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Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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Fair value of the assets less the liabilities of a derivative or group of derivatives.

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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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Nominal mass used to calculate payments on a derivative instrument.

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