Segment Reporting Schedule of Revenue by Geographic Location (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Sales	$ 202,253	$ 177,917	$ 584,937	$ 543,544
UNITED STATES
Disaggregation of Revenue [Line Items]
Sales	157,969	129,654	447,585	395,207
PE Films [Member]
Disaggregation of Revenue [Line Items]
Sales	28,501	26,440	87,885	103,444
PE Films [Member] | Surface Protection Films [Member]
Disaggregation of Revenue [Line Items]
Sales	20,905	19,868	65,997	79,919
PE Films [Member] | Films For Other Markets [Member]
Disaggregation of Revenue [Line Items]
Sales	0	1,530	0	6,263
PE Films [Member] | Film Products Subtotal [Member]
Disaggregation of Revenue [Line Items]
Sales	28,501	26,440	87,885	103,444
Flexible Packaging Films [Member] [Domain]
Disaggregation of Revenue [Line Items]
Sales	36,666	35,856	102,560	100,534
Aluminum Extrusions [Member]
Disaggregation of Revenue [Line Items]
Sales	137,086	115,621	394,492	339,566
Aluminum Extrusions [Member] | Nonresidential Building And Construction [Member]
Disaggregation of Revenue [Line Items]
Sales	68,590	62,611	195,941	190,476
Aluminum Extrusions [Member] | Consumer Durables [Member]
Disaggregation of Revenue [Line Items]
Sales	12,873	11,160	39,611	31,491
Aluminum Extrusions [Member] | Distribution [Member]
Disaggregation of Revenue [Line Items]
Sales	12,693	7,796	30,478	22,055
Aluminum Extrusions [Member] | Automotive [Member]
Disaggregation of Revenue [Line Items]
Sales	10,150	10,332	32,750	25,375
Aluminum Extrusions [Member] | Residential Building And Construction [Member]
Disaggregation of Revenue [Line Items]
Sales	13,154	10,149	39,755	29,016
Aluminum Extrusions [Member] | Aluminum Extrusions Subtotal [Member]
Disaggregation of Revenue [Line Items]
Sales	137,086	115,621	394,492	339,566
Aluminum Extrusions [Member] | Machinery and Equipment BNL [Domain]
Disaggregation of Revenue [Line Items]
Sales	11,611	7,581	31,190	23,147
Aluminum Extrusions [Member] | Electrical [Member]
Disaggregation of Revenue [Line Items]
Sales	8,015	5,992	24,767	18,006
Exports From United States [Member] | Asia [Member]
Disaggregation of Revenue [Line Items]
Sales	12,609	14,255	43,129	59,816
Revenues	7,400	5,900	25,000	25,100
Exports From United States [Member] | CANADA
Disaggregation of Revenue [Line Items]
Sales	4,107	7,200	14,145	13,359
Exports From United States [Member] | Europe [Member]
Disaggregation of Revenue [Line Items]
Sales	1,343	1,468	3,323	4,272
Exports From United States [Member] | Latin America [Member]
Disaggregation of Revenue [Line Items]
Sales	1,170	465	3,630	1,953
Operations Outside United States [Member] | BRAZIL
Disaggregation of Revenue [Line Items]
Sales	$ 25,055	$ 24,875	$ 73,125	$ 68,937