Segment Reporting (Schedule Of Segment Reporting Information By Segment) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Segment Reporting Information [Line Items]
Assets	$ 749,377		$ 707,373
Total net sales	239,445	$ 249,921
Gross Sales	248,466	258,711
Total Segment Income (Loss)	16,477	24,843
Interest income	59	56
Interest expense	1,232	1,644
Gain (loss) on investment in kaléo accounted for under fair value method	17,082	8,200
Gain (Loss) on Disposition of Assets	(385)	0
Stock option-based compensation costs	415	86
Corporate expenses, net	8,160	7,918
Income from continuing operations before income taxes	23,811	23,451
Income taxes from continuing operations	4,026	5,287
Net income	19,785	18,164
kaleo
Segment Reporting Information [Line Items]
Gain (loss) on investment in kaléo accounted for under fair value method	17,082	8,200
PE Films
Segment Reporting Information [Line Items]
Assets	234,301		231,720
Total net sales	66,779	93,249
Operating profit from ongoing operations	2,951	14,034
Plant shutdowns, asset impairments, restructurings and other	(1,378)	(1,052)
Flexible Packaging Films [Member] [Domain]
Segment Reporting Information [Line Items]
Assets	59,550		58,964
Total net sales	33,619	28,437
Operating profit from ongoing operations	2,859	1,715
Plant shutdowns, asset impairments, restructurings and other	0	0
Aluminum Extrusions
Segment Reporting Information [Line Items]
Assets	302,153		$ 281,372
Total net sales	139,047	128,235
Operating profit from ongoing operations	12,085	10,199
Plant shutdowns, asset impairments, restructurings and other	(40)	(53)
Shipping and Handling [Member]
Segment Reporting Information [Line Items]
Freight	9,021	8,790
Personal Care Materials [Member] \| PE Films
Segment Reporting Information [Line Items]
Total net sales	44,855	61,644
Surface Protection Films [Member] \| PE Films
Segment Reporting Information [Line Items]
Total net sales	19,888	29,815
Films For Other Markets [Member] \| PE Films
Segment Reporting Information [Line Items]
Total net sales	2,036	1,790
Film Products Subtotal [Member] \| PE Films
Segment Reporting Information [Line Items]
Total net sales	66,779	93,249
Nonresidential Building And Construction [Member] \| Aluminum Extrusions
Segment Reporting Information [Line Items]
Total net sales	69,638	65,280
Consumer Durables [Member] \| Aluminum Extrusions
Segment Reporting Information [Line Items]
Total net sales	15,545	15,189
Distribution [Member] \| Aluminum Extrusions
Segment Reporting Information [Line Items]
Total net sales	8,573	10,971
Automotive [Member] \| Aluminum Extrusions
Segment Reporting Information [Line Items]
Total net sales	12,627	9,673
Residential Building And Construction [Member] \| Aluminum Extrusions
Segment Reporting Information [Line Items]
Total net sales	11,672	9,601
Machinery and Equipment BNL [Domain] \| Aluminum Extrusions
Segment Reporting Information [Line Items]
Total net sales	9,923	9,094
Electrical [Member] \| Aluminum Extrusions
Segment Reporting Information [Line Items]
Total net sales	11,069	8,427
Aluminum Extrusions Subtotal [Member] \| Aluminum Extrusions
Segment Reporting Information [Line Items]
Total net sales	139,047	128,235
Product [Member]
Segment Reporting Information [Line Items]
Freight	$ 200,653	$ 203,189

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