Segment Reporting Schedule of Revenue by Geographic Location (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Net Sales	$ 249,921	$ 212,720
UNITED STATES
Disaggregation of Revenue [Line Items]
Net Sales	159,562	129,901
PE Films
Disaggregation of Revenue [Line Items]
Net Sales	93,249	86,411
PE Films \| Personal Care Materials [Member]
Disaggregation of Revenue [Line Items]
Net Sales	61,644	61,299
PE Films \| Surface Protection Films [Member]
Disaggregation of Revenue [Line Items]
Net Sales	29,815	23,441
PE Films \| Films For Other Markets [Member]
Disaggregation of Revenue [Line Items]
Net Sales	1,790	1,672
PE Films \| Film Products Subtotal [Member]
Disaggregation of Revenue [Line Items]
Net Sales	93,249	86,412
Flexible Packaging Films [Member] [Domain]
Disaggregation of Revenue [Line Items]
Net Sales	28,437	26,710
Aluminum Extrusions
Disaggregation of Revenue [Line Items]
Net Sales	128,235	99,599
Aluminum Extrusions \| Nonresidential Building And Construction [Member]
Disaggregation of Revenue [Line Items]
Net Sales	65,280	52,210
Aluminum Extrusions \| Consumer Durables [Member]
Disaggregation of Revenue [Line Items]
Net Sales	15,189	12,097
Aluminum Extrusions \| Distribution [Member]
Disaggregation of Revenue [Line Items]
Net Sales	10,971	6,334
Aluminum Extrusions \| Automotive [Member]
Disaggregation of Revenue [Line Items]
Net Sales	9,673	10,174
Aluminum Extrusions \| Residential Building And Construction [Member]
Disaggregation of Revenue [Line Items]
Net Sales	9,601	7,272
Aluminum Extrusions \| Aluminum Extrusions Subtotal [Member]
Disaggregation of Revenue [Line Items]
Net Sales	128,235	99,598
Aluminum Extrusions \| Machinery and Equipment BNL [Domain]
Disaggregation of Revenue [Line Items]
Net Sales	9,094	7,205
Aluminum Extrusions \| Electrical [Member]
Disaggregation of Revenue [Line Items]
Net Sales	8,427	4,306
Exports From United States [Member] \| Asia [Member]
Disaggregation of Revenue [Line Items]
Net Sales	23,592	18,722
Exports From United States [Member] \| CANADA
Disaggregation of Revenue [Line Items]
Net Sales	13,298	13,092
Exports From United States [Member] \| Europe [Member]
Disaggregation of Revenue [Line Items]
Net Sales	1,822	2,358
Exports From United States [Member] \| Latin America [Member]
Disaggregation of Revenue [Line Items]
Net Sales	3,052	3,730
Operations Outside United States [Member] \| BRAZIL
Disaggregation of Revenue [Line Items]
Net Sales	23,151	21,360
Operations Outside United States [Member] \| NETHERLANDS
Disaggregation of Revenue [Line Items]
Net Sales	11,928	12,760
Operations Outside United States [Member] \| HUNGARY
Disaggregation of Revenue [Line Items]
Net Sales	8,818	5,191
Operations Outside United States [Member] \| CHINA
Disaggregation of Revenue [Line Items]
Net Sales	2,274	3,405
Operations Outside United States [Member] \| INDIA
Disaggregation of Revenue [Line Items]
Net Sales	$ 2,424	$ 2,201