Segment Reporting Schedule of Revenue by Geographic Location (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Sales	$ 211,174	$ 239,361	$ 430,896	$ 478,807
UNITED STATES
Disaggregation of Revenue [Line Items]
Sales	141,559	162,788	287,742	335,042
PE Films
Disaggregation of Revenue [Line Items]
Sales	71,012	69,161	142,273	135,941
PE Films \| Personal Care Materials [Member]
Disaggregation of Revenue [Line Items]
Sales	36,258	37,956	77,488	82,812
PE Films \| Surface Protection Films [Member]
Disaggregation of Revenue [Line Items]
Sales	31,699	29,253	60,052	49,142
PE Films \| Films For Other Markets [Member]
Disaggregation of Revenue [Line Items]
Sales	3,055	1,952	4,733	3,987
PE Films \| Film Products Subtotal [Member]
Disaggregation of Revenue [Line Items]
Sales	71,012	69,161	142,273	135,941
Flexible Packaging Films [Member] [Domain]
Disaggregation of Revenue [Line Items]
Sales	34,104	33,443	64,678	67,062
Aluminum Extrusions [Member]
Disaggregation of Revenue [Line Items]
Sales	106,058	136,757	223,945	275,804
Aluminum Extrusions [Member] \| Nonresidential Building And Construction [Member]
Disaggregation of Revenue [Line Items]
Sales	64,726	69,019	127,865	138,657
Aluminum Extrusions [Member] \| Consumer Durables [Member]
Disaggregation of Revenue [Line Items]
Sales	7,782	16,381	20,331	31,926
Aluminum Extrusions [Member] \| Distribution [Member]
Disaggregation of Revenue [Line Items]
Sales	6,521	8,739	14,259	17,312
Aluminum Extrusions [Member] \| Automotive [Member]
Disaggregation of Revenue [Line Items]
Sales	5,572	12,496	15,043	25,123
Aluminum Extrusions [Member] \| Residential Building And Construction [Member]
Disaggregation of Revenue [Line Items]
Sales	9,052	10,278	18,867	21,950
Aluminum Extrusions [Member] \| Aluminum Extrusions Subtotal [Member]
Disaggregation of Revenue [Line Items]
Sales	106,058	136,757	223,945	275,804
Aluminum Extrusions [Member] \| Machinery and Equipment BNL [Domain]
Disaggregation of Revenue [Line Items]
Sales	7,630	9,471	15,566	19,394
Aluminum Extrusions [Member] \| Electrical [Member]
Disaggregation of Revenue [Line Items]
Sales	4,775	10,373	12,014	21,442
Exports From United States [Member] \| Asia [Member]
Disaggregation of Revenue [Line Items]
Sales	23,643	24,513	45,807	38,006	$ 32,100
Revenues	10,000	7,500	19,300	12,700
Exports From United States [Member] \| CANADA
Disaggregation of Revenue [Line Items]
Sales	1,854	5,872	6,752	9,477
Exports From United States [Member] \| Europe [Member]
Disaggregation of Revenue [Line Items]
Sales	1,562	1,517	3,063	2,877
Exports From United States [Member] \| Latin America [Member]
Disaggregation of Revenue [Line Items]
Sales	2,078	2,670	5,212	5,537
Operations Outside United States [Member] \| BRAZIL
Disaggregation of Revenue [Line Items]
Sales	25,739	27,582	51,687	55,721
Operations Outside United States [Member] \| NETHERLANDS
Disaggregation of Revenue [Line Items]
Sales	7,132	8,450	15,017	18,037
Operations Outside United States [Member] \| HUNGARY
Disaggregation of Revenue [Line Items]
Sales	5,751	5,162	12,355	11,996
Operations Outside United States [Member] \| CHINA
Disaggregation of Revenue [Line Items]
Sales	0	0	0	230
Operations Outside United States [Member] \| INDIA
Disaggregation of Revenue [Line Items]
Sales	$ 1,856	$ 807	$ 3,261	$ 1,884