Segment Reporting (Schedule Of Segment Reporting Information By Segment) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Segment Reporting Information [Line Items]
Assets	$ 755,610		$ 755,743
Total net sales	249,921	$ 212,720
Add back freight	8,790	8,306
Sales as shown in the Consolidated Statements of Income	258,711	221,026
Total Segment Income (Loss)	24,843	10,453
Interest income	56	74
Interest expense	1,644	1,180
Gain (loss) on investment in kaléo accounted for under fair value method	8,200	3,300
Gain (Loss) on Disposition of Assets	0	164
Stock option-based compensation costs	86	3
Corporate expenses, net	7,918	6,523
Income from continuing operations before income taxes	23,451	6,121
Income taxes from continuing operations	5,287	2,418
Net income	18,164	3,703
kaleo
Segment Reporting Information [Line Items]
Gain (loss) on investment in kaléo accounted for under fair value method	8,200	3,300
PE Films
Segment Reporting Information [Line Items]
Assets	293,662		289,514
Total net sales	93,249	86,411
Operating profit from ongoing operations	14,034	9,031
Plant shutdowns, asset impairments, restructurings and other	(1,052)	(2,068)
Flexible Packaging Films [Member] [Domain]
Segment Reporting Information [Line Items]
Assets	47,810		49,915
Total net sales	28,437	26,710
Operating profit from ongoing operations	1,715	(1,998)
Plant shutdowns, asset impairments, restructurings and other	0	0
Aluminum Extrusions
Segment Reporting Information [Line Items]
Assets	272,609		$ 268,127
Total net sales	128,235	99,599
Operating profit from ongoing operations	10,199	9,829
Plant shutdowns, asset impairments, restructurings and other	$ (53)	$ (4,341)