Business Segments (Schedule Of Identifiable Assets) (Details) - USD ($) $ in Thousands		Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2016
Revenue from External Customer [Line Items]
Identifiable Assets, Total	[1]	$ 712,668		$ 707,373
Cash and cash equivalents		31,422	[1]	34,397	[1]	$ 36,491	$ 29,511
PE Films [Member]
Revenue from External Customer [Line Items]
Identifiable Assets, Total		230,415		231,720
Flexible Packaging Films [Member] [Domain]
Revenue from External Customer [Line Items]
Identifiable Assets, Total		74,016		58,964
General Corporate
Revenue from External Customer [Line Items]
Identifiable Assets, Total	[1],[2]	111,788		100,920
Subtotal
Revenue from External Customer [Line Items]
Identifiable Assets, Total		569,458		572,056
Aluminum Extrusions
Revenue from External Customer [Line Items]
Identifiable Assets, Total		$ 265,027		$ 281,372

[1] Information on exports and foreign operations are provided on the previous page. Cash and cash equivalents includes funds held in locations outside the U.S. of $23.0 million and $31.1 million at December 31, 2019 and 2018, respectively. Export sales relate almost entirely to PE Films. Operations outside the U.S. in The Netherlands, Hungary, China and India also relate to PE Films. Operations in Brazil are primarily related to Flexible Packaging Films, but also include PE Films operations. Sales from locations in The Netherlands and Hungary are primarily to customers located in Europe. Sales from locations in China (Guangzhou and Shanghai) are primarily to customers located in China, but also include other customers in Asia.

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