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Derivative Financial Instruments (Narrative) (Details) R$ in Thousands, $ in Thousands, lbs in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2020 BRL (R$)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($) lbs	Sep. 30, 2020 BRL (R$) lbs	Dec. 31, 2019 USD ($) lbs
Derivative [Line Items]
Amounts of unrealized after tax gains (losses) to be Reclassified within Twelve Months		$ 100
Aluminum Futures Contracts
Derivative [Line Items]
Derivative, Notional Amount			$ 15,700		$ 20,200
Net asset (liability), Fair Value			$ (124)		$ (1,253)
Commitment Under Cash Flow Hedges, Mass | lbs			16.8	16.8	19.6
Terphane Ltda [Member]
Derivative [Line Items]
Derivative, Notional Amount			$ 18,450	R$ 91,056
Accrued Expenses [Member] | Derivatives Designated As Hedging Instruments [Member] | Aluminum Futures Contracts
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset			659		$ 6
Derivative Liability, Fair Value, Gross Liability			783		$ 1,259
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			$ 2,400
Oct-2018 [Member] | Terphane Ltda [Member]
Derivative [Line Items]
Annual Net Costs Mismatch Translation Exposure - Real vs US Dollar | R$	R$ 134,000

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

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