Goodwill And Other Intangible Assets Goodwill and Other Intangible Assets (Rollforward Schedule of Identifiable Intangibles) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net	$ 18,820
PE Films [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net	0	$ 610	$ 730
Amortization	(120)	(120)
Disposal Group, Including Discontinued Operation, Intangible Assets	(490)
Flexible Packaging Films [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net	1,621	2,327	2,811
Amortization	(397)	(426)
Finite Lived Intangible Assets, Foreign Currency Translation Gain (Loss)	(309)	(58)
Impairment of Intangible Assets, Finite-lived		0
Aluminum Extrusions [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net	17,199	19,699	32,754
Amortization	(2,500)	(13,055)
Impairment of Intangible Assets, Finite-lived	0	(10,040)	0
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net	17,551	20,198
Customer Relationships [Member] | PE Films [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net	0	0	0
Amortization	0	0
Disposal Group, Including Discontinued Operation, Intangible Assets	0
Customer Relationships [Member] | Flexible Packaging Films [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net	387	554	661
Amortization	(84)	(91)
Finite Lived Intangible Assets, Foreign Currency Translation Gain (Loss)	(83)	(16)
Impairment of Intangible Assets, Finite-lived		0
Customer Relationships [Member] | Aluminum Extrusions [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net	17,164	19,644	22,124
Amortization	(2,480)	(2,480)
Proprietary Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net	194	895
Proprietary Technology [Member] | PE Films [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net	0	610	730
Amortization	(120)	(120)
Disposal Group, Including Discontinued Operation, Intangible Assets	(490)
Proprietary Technology [Member] | Flexible Packaging Films [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net	159	230	288
Amortization	(53)	(55)
Finite Lived Intangible Assets, Foreign Currency Translation Gain (Loss)	(18)	(3)
Impairment of Intangible Assets, Finite-lived		0
Proprietary Technology [Member] | Aluminum Extrusions [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net	35	55	75
Amortization	(20)	(20)
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net	1,075	1,543
Trade Names [Member] | PE Films [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net	0	0	0
Amortization	0	0
Disposal Group, Including Discontinued Operation, Intangible Assets	0
Finite Lived Intangible Assets, Foreign Currency Translation Gain (Loss)	(208)
Trade Names [Member] | Flexible Packaging Films [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net	1,075	1,543	1,862
Amortization	(260)	(280)
Finite Lived Intangible Assets, Foreign Currency Translation Gain (Loss)		(39)
Impairment of Intangible Assets, Finite-lived		0
Trade Names [Member] | Aluminum Extrusions [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net	0	0	$ 10,555
Amortization	$ 0	$ (10,555)