Financial Instruments (Summary Of Location And Fair Value Of 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
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] | Accrued Expenses
Derivatives, Fair Value [Line Items]
Asset derivatives	387
Net asset (liability)		(852)
Flexible Packaging Films [Member] [Domain] | Designated as Hedging Instrument | Accrued Expenses
Derivatives, Fair Value [Line Items]
Asset derivatives	853	83
Liability derivatives: Aluminum futures contracts	466	935
Aluminum Futures Contracts
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 | Prepaid Expenses and Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Net asset (liability)	1,538
Aluminum Futures Contracts | Accrued Expenses
Derivatives, Fair Value [Line Items]
Net asset (liability)		(1,253)
Aluminum Futures Contracts | Designated as Hedging Instrument | Prepaid Expenses and Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives	1,560
Liability derivatives: Aluminum futures contracts	(22)
Aluminum Futures Contracts | Designated as Hedging Instrument | Accrued Expenses
Derivatives, Fair Value [Line Items]
Asset derivatives		6
Liability derivatives: Aluminum futures contracts		(1,259)
Selling, General and Administrative Expenses [Member] | Flexible Packaging Films [Member] [Domain]
Derivatives, Fair Value [Line Items]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	(4,437)	(856)	(2,105)
Cost of Sales [Member] | Flexible Packaging Films [Member] [Domain]
Derivatives, Fair Value [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	62	62	62
Cost of Sales [Member] | Aluminum Futures Contracts
Derivatives, Fair Value [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(2,717)	(2,736)	1,069
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Foreign Currency Forward Contracts
Derivatives, Fair Value [Line Items]
Cost of Goods and Services Sold	(62)	(62)	62
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Aluminum Futures Contracts
Derivatives, Fair Value [Line Items]
Cost of Goods and Services Sold	2,717	2,736	(1,069)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Selling, General and Administrative Expenses [Member] | Foreign Currency Forward Contracts
Derivatives, Fair Value [Line Items]
Cost of Goods and Services Sold	$ (6,069)	$ (904)	$ (1,796)