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Derivative Financial Instruments (Narrative) (Details) R$ in Thousands, $ in Thousands, lb in Millions	6 Months Ended		12 Months Ended
	Jun. 30, 2019 BRL (R$) lb	Jun. 30, 2019 USD ($) lb	Dec. 31, 2018 USD ($) lb	Jun. 30, 2019 USD ($)
Derivative [Line Items]
Amounts of unrealized after tax gains (losses) to be Reclassified within Twelve Months		$ 1,300
Aluminum Futures Contracts
Derivative [Line Items]
Notional Amount			$ 25,400	$ 19,800
Weight of aluminum that hedged future purchase of aluminum to meet fixed - price forward sales contract obligations, lbs | lb	18.0	18.0	22.5
Net asset (liability), Fair Value			$ (1,630)	(1,845)
Terphane Ltda [Member]
Derivative [Line Items]
Notional Amount	R$ 107,328			27,600
Accrued Expenses [Member] | Derivatives Designated As Hedging Instruments [Member] | Aluminum Futures Contracts
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset			20	0
Derivative Liability, Fair Value, Gross Liability			$ 1,650	1,845
Cash Flow Hedging [Member] | Foreign Currency Forwwards And Options [Member]
Derivative [Line Items]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax				$ 500
Oct-2018 [Member] | Terphane Ltda [Member]
Derivative [Line Items]
Annual Net Costs Mismatch Translation Exposure - Real vs US Dollar | R$	R$ 125,000

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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
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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.

+ References

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-SubTopic 30
-Section 50
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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 of the assets less the liabilities of a derivative or group of derivatives.

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Fair value as of the balance sheet date of all foreign currency derivatives designated as cash flow hedging instruments.

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