Segment Reporting (Schedule Of Segment Reporting Information By Segment) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Total net sales	$ 204,085	$ 180,365	$ 382,684	$ 365,627
Sales as shown in the consolidated statements of income	211,129	186,259	395,951	378,396
Brazil One-time Tax Credit PIS/COFINS	8,486	0	8,486	0
Goodwill, Impairment Loss	0	0	0	(13,696)
Amortization of identifiable intangibles	723	753	1,446	1,511
Goodwill, Impairment Loss, Net of Tax				10,500
Total Segment Income (Loss)	38,847	27,574	62,990	37,770
Interest income	25	5	32	32
Interest expense	891	549	1,713	1,104
Gain (loss) on investment in kaléo accounted for under fair value method			600	(24,800)
Stock option-based compensation costs	675	683	1,144	1,258
Corporate expenses, net	11,055	9,455	21,917	19,338
Income from continuing operations before income taxes	26,451	18,192	39,166	(8,698)
Income taxes from continuing operations	5,723	3,860	8,820	(2,366)
Income from continuing operations	20,728	14,332	30,346	(6,332)
Net Income (Loss) Attributable to Parent	21,236	11,196	30,267	(11,126)
Income (loss) from discontinued operations, net of tax	508	(3,136)	(79)	(4,794)
kaleo
Segment Reporting Information [Line Items]
Gain (loss) on investment in kaléo accounted for under fair value method	(200)	(1,300)	918	(24,800)
PE Films [Member]
Segment Reporting Information [Line Items]
Total net sales	31,430	40,203	59,384	77,004
EBITDA	(151)	(139)	(275)	(167)
Earnings before interest, taxes, depreciation and amortization (EBITDA)	9,001	15,471	16,213	27,884
Depreciation, Depletion and Amortization	(1,671)	(1,589)	(3,090)	(3,083)
Earnings before interest and taxes (EBIT)	7,330	13,882	13,123	24,801
Flexible Packaging Films [Member] [Domain]
Segment Reporting Information [Line Items]
Total net sales	33,374	34,104	65,895	64,678
EBITDA	8,452	(10)	8,414	(10)
Aluminum Extrusions [Member]
Segment Reporting Information [Line Items]
Total net sales	139,281	106,058	257,405	223,945
EBITDA	(246)	(1,230)	(63)	(1,918)
Goodwill, Impairment Loss	0	0	0	13,696
Amortization of identifiable intangibles				(13,696)
Earnings before interest, taxes, depreciation and amortization (EBITDA)	19,723	13,279	33,024	24,956
Depreciation, Depletion and Amortization	(4,032)	(4,267)	(8,162)	(8,380)
Earnings before interest and taxes (EBIT)	15,691	9,012	24,862	16,576
Flexible Packaging Films [Member]
Segment Reporting Information [Line Items]
Earnings before interest, taxes, depreciation and amortization (EBITDA)	8,277	6,495	17,901	13,048
Depreciation, Depletion and Amortization	(506)	(436)	(972)	(864)
Earnings before interest and taxes (EBIT)	7,771	6,059	16,929	12,184
Shipping and Handling [Member]
Segment Reporting Information [Line Items]
Cost of goods sold	7,044	5,894	13,267	12,769
Personal Care Materials [Member] \| PE Films [Member]
Segment Reporting Information [Line Items]
Total net sales	6,940	5,449	14,293	12,219
Surface Protection Films [Member] \| PE Films [Member]
Segment Reporting Information [Line Items]
Total net sales	24,490	31,699	45,091	60,052
Films For Other Markets [Member] \| PE Films [Member]
Segment Reporting Information [Line Items]
Total net sales	0	3,055	0	4,733
Film Products Subtotal [Member] \| PE Films [Member]
Segment Reporting Information [Line Items]
Total net sales	31,430	40,203	59,384	77,004
Nonresidential Building And Construction [Member] \| Aluminum Extrusions [Member]
Segment Reporting Information [Line Items]
Total net sales	70,122	64,726	127,350	127,865
Consumer Durables [Member] \| Aluminum Extrusions [Member]
Segment Reporting Information [Line Items]
Total net sales	13,586	7,782	26,738	20,331
Distribution [Member] \| Aluminum Extrusions [Member]
Segment Reporting Information [Line Items]
Total net sales	10,269	6,521	17,785	14,259
Automotive [Member] \| Aluminum Extrusions [Member]
Segment Reporting Information [Line Items]
Total net sales	11,185	5,572	22,600	15,043
Residential Building And Construction [Member] \| Aluminum Extrusions [Member]
Segment Reporting Information [Line Items]
Total net sales	13,893	9,052	26,601	18,867
Machinery and Equipment BNL [Domain] \| Aluminum Extrusions [Member]
Segment Reporting Information [Line Items]
Total net sales	10,654	7,630	19,579	15,566
Electrical [Member] \| Aluminum Extrusions [Member]
Segment Reporting Information [Line Items]
Total net sales	9,572	4,775	16,752	12,014
Aluminum Extrusions Subtotal [Member] \| Aluminum Extrusions [Member]
Segment Reporting Information [Line Items]
Total net sales	139,281	106,058	257,405	223,945
Product [Member]
Segment Reporting Information [Line Items]
Cost of goods sold	$ 158,692	$ 134,035	$ 299,977	$ 279,204

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