Business Segments (Schedule Of Segment Reporting Information By Segment) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2023	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenue from External Customer [Line Items]
Net Sales			$ 677,892	$ 903,582	$ 798,223
Sales			704,825	938,564	826,455
Total			(17,271)	79,016	102,108
Interest income			522	57	73
Interest expense			11,607	4,990	3,386
Stock option-based compensation expense			231	1,424	2,495
Pension settlement loss	$ 66,700	$ 25,600	92,291	0	0
Corporate expenses, net			39,414	41,221	41,970
Income (loss) before income taxes			(160,030)	32,844	67,110
Income tax expense (benefit)			(54,125)	4,389	9,284
Net income (loss)			(105,905)	28,455	57,826
kaleo
Revenue from External Customer [Line Items]
Gain (loss) on investment accounted for under the fair value method			262	1,406	12,780
PE Films
Revenue from External Customer [Line Items]
Net Sales			76,763	97,571	118,920
Earnings before interest, taxes, depreciation and amortization (EBITDA)			11,217	11,949	27,694
Cost, Depreciation and Amortization			6,522	6,280	6,263
Earnings before interest and taxes (EBIT)			4,695	5,669	21,431
Plant shutdowns, asset impairments, restructurings and other			(4,972)	(646)	(371)
Aluminum Extrusions
Revenue from External Customer [Line Items]
Net Sales			474,803	637,872	539,325
Earnings before interest, taxes, depreciation and amortization (EBITDA)			37,976	66,800	55,948
Cost, Depreciation and Amortization			17,927	17,414	16,272
Earnings before interest and taxes (EBIT)			20,049	49,386	39,676
Plant shutdowns, asset impairments, restructurings and other			(3,557)	(310)	3,237
Flexible Packaging Films
Revenue from External Customer [Line Items]
Net Sales			126,326	168,139	139,978
Plant shutdowns, asset impairments, restructurings and other			(113)	(91)	8,439
PET Films
Revenue from External Customer [Line Items]
Earnings before interest, taxes, depreciation and amortization (EBITDA)			4,383	27,452	31,684
Cost, Depreciation and Amortization			2,865	2,444	1,988
Earnings before interest and taxes (EBIT)			1,518	25,008	29,696
Freight
Revenue from External Customer [Line Items]
Cost of Goods and Services Sold			$ 26,933	$ 34,982	$ 28,232