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Derivative Financial Instruments (Narrative) (Details) R$ in Thousands, $ in Thousands, lb in Millions | 3 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Mar. 31, 2019 USD ($) lb | Dec. 31, 2018 USD ($) lb | Mar. 31, 2019 BRL (R$) | Mar. 31, 2019 USD ($)
Derivative [Line Items] |  |  |  |
Amounts of unrealized after tax gains (losses) to be Reclassified within Twelve Months | $ 1,200 |  |  |
Aluminum Futures Contracts |  |  |  |
Derivative [Line Items] |  |  |  |
Notional Amount |  | $ 25,400 |  | $ 24,600
Weight of aluminum that hedged future purchase of aluminum to meet fixed - price forward sales contract obligations, lbs | lb | 22.2 | 22.5 |  |
Net asset (liability), Fair Value |  | $ (1,630) |  | (1,259)
Terphane Ltda [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Notional Amount |  |  | R$ 129,682 | 33,675
Accrued Expenses [Member] | Derivatives Designated As Hedging Instruments [Member] | Aluminum Futures Contracts |  |  |  |
Derivative [Line Items] |  |  |  |
Derivative Asset, Fair Value, Gross Asset |  | 20 |  | 25
Derivative Liability, Fair Value, Gross Liability |  | $ 1,650 |  | 1,284
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 |  |  |  | $ 1,500
Oct-2018 [Member] | Terphane Ltda [Member] |  |  |  |
Derivative [Line Items] |  |  |  |
Annual Net Costs Mismatch Translation Exposure - Real vs US Dollar | $ 125,000 |  |  |

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- 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 + Details
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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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=112277219&loc=d3e80748-113994 + Details
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- Definition 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 Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226000-175313 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 20 -Section 50 -Paragraph 4D -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=109247956&loc=SL51823488-111719 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -Subparagraph (a),(c) -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624163-113959 + Details
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- Definition Fair value of the assets less the liabilities of a derivative or group of derivatives. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13433-108611 + Details
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