Segment Reporting (Schedule Of Identifiable Assets By Segment) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Stock option-based compensation costs	$ 415	$ 111	$ 806	$ 153
Subtotal	562,577		562,577		$ 607,556
General corporate	91,583		91,583		111,696
Cash and cash equivalents	36,776	$ 31,850	36,776	$ 31,850	36,491	$ 29,511
Total assets	690,936		690,936		755,743
PE Films
Total assets	231,106		231,106		289,514
Flexible Packaging Films [Member] [Domain]
Total assets	53,661		53,661		49,915
Aluminum Extrusions
Total assets	$ 277,810		$ 277,810		$ 268,127