Segment Reporting Schedule of Revenue by Geographic Location (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Sales	$ 239,361	$ 255,319	$ 478,807	$ 505,241
UNITED STATES
Disaggregation of Revenue [Line Items]
Sales	162,788	171,185	335,042	330,747
PE Films
Disaggregation of Revenue [Line Items]
Sales	69,161	82,457	135,941	175,707
PE Films \| Personal Care Materials [Member]
Disaggregation of Revenue [Line Items]
Sales	37,956	55,985	82,812	117,629
PE Films \| Surface Protection Films [Member]
Disaggregation of Revenue [Line Items]
Sales	29,253	24,918	49,142	54,733
PE Films \| Films For Other Markets [Member]
Disaggregation of Revenue [Line Items]
Sales	1,952	1,555	3,987	3,345
PE Films \| Film Products Subtotal [Member]
Disaggregation of Revenue [Line Items]
Sales	69,161	82,458	135,941	175,707
Flexible Packaging Films [Member] [Domain]
Disaggregation of Revenue [Line Items]
Sales	33,443	28,304	67,062	56,741
Aluminum Extrusions
Disaggregation of Revenue [Line Items]
Sales	136,757	144,558	275,804	272,793
Aluminum Extrusions \| Nonresidential Building And Construction [Member]
Disaggregation of Revenue [Line Items]
Sales	69,019	72,442	138,657	137,629
Aluminum Extrusions \| Consumer Durables [Member]
Disaggregation of Revenue [Line Items]
Sales	16,381	17,161	31,926	32,309
Aluminum Extrusions \| Distribution [Member]
Disaggregation of Revenue [Line Items]
Sales	8,739	12,031	17,312	22,961
Aluminum Extrusions \| Automotive [Member]
Disaggregation of Revenue [Line Items]
Sales	12,496	11,157	25,123	20,787
Aluminum Extrusions \| Residential Building And Construction [Member]
Disaggregation of Revenue [Line Items]
Sales	10,278	12,343	21,950	21,813
Aluminum Extrusions \| Aluminum Extrusions Subtotal [Member]
Disaggregation of Revenue [Line Items]
Sales	136,757	144,557	275,804	272,793
Aluminum Extrusions \| Machinery and Equipment BNL [Domain]
Disaggregation of Revenue [Line Items]
Sales	9,471	9,867	19,394	19,144
Aluminum Extrusions \| Electrical [Member]
Disaggregation of Revenue [Line Items]
Sales	10,373	9,556	21,442	18,150
Exports From United States [Member] \| Asia [Member]
Disaggregation of Revenue [Line Items]
Sales	24,513	18,884	38,006	42,476
Exports From United States [Member] \| CANADA
Disaggregation of Revenue [Line Items]
Sales	5,872	14,239	9,477	27,537
Exports From United States [Member] \| Europe [Member]
Disaggregation of Revenue [Line Items]
Sales	1,517	1,697	2,877	3,519
Exports From United States [Member] \| Latin America [Member]
Disaggregation of Revenue [Line Items]
Sales	2,670	3,654	5,537	6,706
Operations Outside United States [Member] \| BRAZIL
Disaggregation of Revenue [Line Items]
Sales	27,582	23,659	55,721	46,811
Operations Outside United States [Member] \| NETHERLANDS
Disaggregation of Revenue [Line Items]
Sales	8,450	11,394	18,037	23,322
Operations Outside United States [Member] \| HUNGARY
Disaggregation of Revenue [Line Items]
Sales	5,162	8,519	11,996	17,337
Operations Outside United States [Member] \| CHINA
Disaggregation of Revenue [Line Items]
Sales	0	1,692	230	3,966
Operations Outside United States [Member] \| INDIA
Disaggregation of Revenue [Line Items]
Sales	$ 807	$ 396	$ 1,884	$ 2,820