Segment Reporting Schedule of Revenue by Geographic Location (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Sales	$ 239,445	$ 249,921
UNITED STATES
Disaggregation of Revenue [Line Items]
Sales	172,254	159,562
PE Films
Disaggregation of Revenue [Line Items]
Sales	66,779	93,249
PE Films \| Personal Care Materials [Member]
Disaggregation of Revenue [Line Items]
Sales	44,855	61,644
PE Films \| Surface Protection Films [Member]
Disaggregation of Revenue [Line Items]
Sales	19,888	29,815
PE Films \| Films For Other Markets [Member]
Disaggregation of Revenue [Line Items]
Sales	2,036	1,790
PE Films \| Film Products Subtotal [Member]
Disaggregation of Revenue [Line Items]
Sales	66,779	93,249
Flexible Packaging Films [Member] [Domain]
Disaggregation of Revenue [Line Items]
Sales	33,619	28,437
Aluminum Extrusions
Disaggregation of Revenue [Line Items]
Sales	139,047	128,235
Aluminum Extrusions \| Nonresidential Building And Construction [Member]
Disaggregation of Revenue [Line Items]
Sales	69,638	65,280
Aluminum Extrusions \| Consumer Durables [Member]
Disaggregation of Revenue [Line Items]
Sales	15,545	15,189
Aluminum Extrusions \| Distribution [Member]
Disaggregation of Revenue [Line Items]
Sales	8,573	10,971
Aluminum Extrusions \| Automotive [Member]
Disaggregation of Revenue [Line Items]
Sales	12,627	9,673
Aluminum Extrusions \| Residential Building And Construction [Member]
Disaggregation of Revenue [Line Items]
Sales	11,672	9,601
Aluminum Extrusions \| Aluminum Extrusions Subtotal [Member]
Disaggregation of Revenue [Line Items]
Sales	139,047	128,235
Aluminum Extrusions \| Machinery and Equipment BNL [Domain]
Disaggregation of Revenue [Line Items]
Sales	9,923	9,094
Aluminum Extrusions \| Electrical [Member]
Disaggregation of Revenue [Line Items]
Sales	11,069	8,427
Exports From United States [Member] \| Asia [Member]
Disaggregation of Revenue [Line Items]
Sales	13,493	23,592
Exports From United States [Member] \| CANADA
Disaggregation of Revenue [Line Items]
Sales	3,605	13,298
Exports From United States [Member] \| Europe [Member]
Disaggregation of Revenue [Line Items]
Sales	1,360	1,822
Exports From United States [Member] \| Latin America [Member]
Disaggregation of Revenue [Line Items]
Sales	2,867	3,052
Operations Outside United States [Member] \| BRAZIL
Disaggregation of Revenue [Line Items]
Sales	28,138	23,151
Operations Outside United States [Member] \| NETHERLANDS
Disaggregation of Revenue [Line Items]
Sales	9,587	11,928
Operations Outside United States [Member] \| HUNGARY
Disaggregation of Revenue [Line Items]
Sales	6,834	8,818
Operations Outside United States [Member] \| CHINA
Disaggregation of Revenue [Line Items]
Sales	230	2,274
Operations Outside United States [Member] \| INDIA
Disaggregation of Revenue [Line Items]
Sales	$ 1,077	$ 2,424