Goodwill And Other Intangible Assets (Reconciliation Of The Beginning And Ending Balance Of Goodwill) (Details) - USD ($) $ in Thousands		12 Months Ended
Feb. 15, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Goodwill, Impairment Loss		$ (46,792)	$ 0	$ 0
Net carrying value of goodwill, beginning of period		128,208	117,822
Acquisitions	$ 10,370	0
Increase (decrease) due to foreign currency translation		(12)	16
Net carrying value of goodwill, end of period		81,404	128,208	117,822
Aluminum Extrusions
Goodwill [Roll Forward]
Goodwill, Impairment Loss		0
Net carrying value of goodwill, beginning of period		24,066	13,696
Increase (decrease) due to foreign currency translation		0	0
Net carrying value of goodwill, end of period		24,066	24,066	13,696
PE Films [Member]
Goodwill [Roll Forward]
Goodwill, Impairment Loss		(46,792)
Net carrying value of goodwill, beginning of period		104,142	104,126
Increase (decrease) due to foreign currency translation		(12)	16
Net carrying value of goodwill, end of period		$ 57,338	$ 104,142	$ 104,126

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

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Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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