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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, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Net asset (liability)	$ (2,188)	$ (2,720)
Aluminum Futures Contracts [Member]
Derivatives, Fair Value [Line Items]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	(2,359)	(1,123)	$ 1,501
Aluminum Futures Contracts [Member] \| Accrued Expenses [Member]
Derivatives, Fair Value [Line Items]
Net asset (liability)	(1,253)	(1,630)
Aluminum Futures Contracts [Member] \| Designated as Hedging Instrument [Member] \| Accrued Expenses [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	6	20
Derivative Liability, Fair Value, Gross Liability	1,259	1,650
Flexible Packaging Films [Member] [Domain] \| Accrued Expenses [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	(852)
Net asset (liability)		(1,053)
Flexible Packaging Films [Member] [Domain] \| Designated as Hedging Instrument [Member] \| Prepaid Expenses And Other [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	83	37
Flexible Packaging Films [Member] [Domain] \| Designated as Hedging Instrument [Member] \| Accrued Expenses [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	$ (935)	$ (1,090)