Goodwill And Other Intangible Assets (Reconciliation Of The Beginning And Ending Balance Of Goodwill) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill [Roll Forward]
Goodwill, Impairment Loss	$ (13,696)	$ 0	$ 0
Net carrying value of goodwill, beginning of period	81,404	81,404
Net carrying value of goodwill, end of period	67,708	81,404	81,404
Aluminum Extrusions
Goodwill [Roll Forward]
Goodwill, Impairment Loss	(13,696)	0	0
Net carrying value of goodwill, beginning of period	24,066	24,066
Net carrying value of goodwill, end of period	10,370	24,066	24,066
PE Films [Member]
Goodwill [Roll Forward]
Goodwill, Impairment Loss	0	0
Net carrying value of goodwill, beginning of period	57,338	57,338
Net carrying value of goodwill, end of period	$ 57,338	$ 57,338	$ 57,338