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

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

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

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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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No definition available.

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Derivative Financial Instruments (Narrative) (Details) R$ in Thousands, $ in Thousands, lb in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2017 lb	Jun. 30, 2018 USD ($) lb	Jun. 30, 2018 BRL (R$)	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Derivative [Line Items]
Amounts of unrealized after tax gains (losses) to be Reclassified within Twelve Months		$ (700)
Aluminum Futures Contracts
Derivative [Line Items]
Notional Amount				$ 18,600	$ 8,200
Weight of aluminum that hedged future purchase of aluminum to meet fixed - price forward sales contract obligations, lbs \| lb	8.0	17.6
Net asset (liability), Fair Value				683	562
Accrued Expenses [Member] \| Derivatives Designated As Hedging Instruments [Member] \| Aluminum Futures Contracts
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset				999	578
Derivative Liability, Fair Value, Gross Liability				316	$ 16
Cost of Sales [Member] \| Foreign Currency Forwards And Options [Member]
Derivative [Line Items]
Notional Amount			R$ 35,900	$ 11,250