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Financial Instruments Financial Instruments (Summary of Location and Fair Value of Currency Forward Derivative Financial Instruments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Net asset (liability)	$ (487)	$ (2,188)
Cost of Goods and Services Sold	558,967	641,140	$ 679,665
Aluminum Futures Contracts [Member]
Derivatives, Fair Value [Line Items]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	74	(2,359)	(1,123)
Aluminum Futures Contracts [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member] \| Gain (loss) on derivative financial instruments
Derivatives, Fair Value [Line Items]
Cost of Goods and Services Sold	2,717	2,736	(1,069)
Aluminum Futures Contracts [Member] \| Prepaid Expenses and Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Net asset (liability)	1,538
Aluminum Futures Contracts [Member] \| Accrued Expenses [Member]
Derivatives, Fair Value [Line Items]
Net asset (liability)		(1,253)
Aluminum Futures Contracts [Member] \| Designated as Hedging Instrument [Member] \| Prepaid Expenses and Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1,560
Derivative Liability, Fair Value, Gross Liability	22
Aluminum Futures Contracts [Member] \| Designated as Hedging Instrument [Member] \| Accrued Expenses [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset		6
Derivative Liability, Fair Value, Gross Liability		1,259
Flexible Packaging Films [Member] [Domain]
Derivatives, Fair Value [Line Items]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	0	0	0
Flexible Packaging Films [Member] [Domain] \| Selling, General and Administrative Expenses [Member]
Derivatives, Fair Value [Line Items]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	(4,437)	(856)	(2,105)
Flexible Packaging Films [Member] [Domain] \| Accrued Expenses [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	387
Net asset (liability)		(852)
Flexible Packaging Films [Member] [Domain] \| Designated as Hedging Instrument [Member] \| Accrued Expenses [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	853	83
Derivative Liability, Fair Value, Gross Liability	(466)	(935)
Foreign Currency Forward Contracts \| Reclassification out of Accumulated Other Comprehensive Income [Member] \| Gain (loss) on derivative financial instruments
Derivatives, Fair Value [Line Items]
Cost of Goods and Services Sold	(62)	(62)	62
Foreign Currency Forward Contracts \| Selling, General and Administrative Expenses [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member] \| Gain (loss) on derivative financial instruments
Derivatives, Fair Value [Line Items]
Cost of Goods and Services Sold	$ (6,069)	$ (904)	$ (1,796)