Segment Reporting (Schedule Of Segment Reporting Information By Segment) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Sales	$ 202,253	$ 177,917	$ 584,937	$ 543,544
Sales as shown in the consolidated statements of income	209,517	184,370	605,468	562,766
Goodwill, Impairment Loss, Net of Tax				10,500
Total Segment Income (Loss)	17,922	24,869	80,911	62,640
Goodwill, Impairment Loss	0	0	0	13,696
Gain (Loss) on Disposition of Assets			0	(45,054)
Income tax expense (benefit)	1,908	(5,942)	10,728	(8,308)
Interest income	8	11	40	43
Interest expense	842	494	2,555	1,598
(Gain) loss on investment in kaléo accounted for under the fair value method			(879)	61,000
Stock option-based compensation costs	675	518	1,819	1,786
Corporate expenses, net	8,555	10,586	30,470	29,915
Income (loss) from continuing operations before income taxes	8,137	(22,918)	47,304	(31,616)
Income from continuing operations	6,229	(16,976)	36,576	(23,308)
Income (loss) from discontinued operations, net of tax	(26)	(48,237)	(104)	(53,031)
Net Income (Loss) Attributable to Parent	6,203	(65,213)	36,472	(76,339)
kaleo [Member]
Segment Reporting Information [Line Items]
(Gain) loss on investment in kaléo accounted for under the fair value method	279	(36,200)	1,197	(61,000)
Aluminum Extrusions [Member]
Segment Reporting Information [Line Items]
Sales	137,086	115,621	394,492	339,566
Earnings before interest, taxes, depreciation and amortization (EBITDA)	12,038	16,540	45,062	41,496
EBITDA	(160)	(720)	(223)	(2,637)
Depreciation, Depletion and Amortization	(3,900)	(4,251)	(12,062)	(12,632)
Earnings before interest and taxes (EBIT)	8,138	12,289	33,000	28,864
Goodwill, Impairment Loss	0	0	0	(13,696)
PE Films [Member]
Segment Reporting Information [Line Items]
Sales	28,501	26,440	87,885	103,444
Earnings before interest, taxes, depreciation and amortization (EBITDA)	4,821	6,041	21,035	33,928
EBITDA	(182)	(56)	(457)	(225)
Depreciation, Depletion and Amortization	(1,591)	(1,785)	(4,681)	(4,868)
Earnings before interest and taxes (EBIT)	3,230	4,256	16,354	29,060
Flexible Packaging Films [Member] [Domain]
Segment Reporting Information [Line Items]
Sales	36,666	35,856	102,560	100,534
EBITDA	(7)	(3)	8,407	(14)
Flexible Packaging Films [Member]
Segment Reporting Information [Line Items]
Earnings before interest, taxes, depreciation and amortization (EBITDA)	7,396	9,546	25,296	22,594
Depreciation, Depletion and Amortization	(493)	(443)	(1,466)	(1,306)
Earnings before interest and taxes (EBIT)	6,903	9,103	23,830	21,288
Shipping and Handling [Member]
Segment Reporting Information [Line Items]
Cost of goods sold	7,264	6,453	20,531	19,222
Surface Protection Films [Member] | PE Films [Member]
Segment Reporting Information [Line Items]
Sales	20,905	19,868	65,997	79,919
Films For Other Markets [Member] | PE Films [Member]
Segment Reporting Information [Line Items]
Sales	0	1,530	0	6,263
Film Products Subtotal [Member] | PE Films [Member]
Segment Reporting Information [Line Items]
Sales	28,501	26,440	87,885	103,444
Nonresidential Building And Construction [Member] | Aluminum Extrusions [Member]
Segment Reporting Information [Line Items]
Sales	68,590	62,611	195,941	190,476
Consumer Durables [Member] | Aluminum Extrusions [Member]
Segment Reporting Information [Line Items]
Sales	12,873	11,160	39,611	31,491
Distribution [Member] | Aluminum Extrusions [Member]
Segment Reporting Information [Line Items]
Sales	12,693	7,796	30,478	22,055
Automotive [Member] | Aluminum Extrusions [Member]
Segment Reporting Information [Line Items]
Sales	10,150	10,332	32,750	25,375
Residential Building And Construction [Member] | Aluminum Extrusions [Member]
Segment Reporting Information [Line Items]
Sales	13,154	10,149	39,755	29,016
Machinery and Equipment BNL [Domain] | Aluminum Extrusions [Member]
Segment Reporting Information [Line Items]
Sales	11,611	7,581	31,190	23,147
Electrical [Member] | Aluminum Extrusions [Member]
Segment Reporting Information [Line Items]
Sales	8,015	5,992	24,767	18,006
Aluminum Extrusions Subtotal [Member] | Aluminum Extrusions [Member]
Segment Reporting Information [Line Items]
Sales	137,086	115,621	394,492	339,566
Product [Member]
Segment Reporting Information [Line Items]
Cost of goods sold	170,756	136,008	470,733	415,212
Overwrap films | PE Films [Member]
Segment Reporting Information [Line Items]
Sales	$ 7,596	$ 5,042	$ 21,888	$ 17,262