Segment Reporting Schedule of Revenue by Geographic Location (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Sales	$ 234,231	$ 257,856	$ 713,038	$ 763,098
UNITED STATES
Disaggregation of Revenue [Line Items]
Sales	156,469	176,022	491,511	506,769
PE Films
Disaggregation of Revenue [Line Items]
Sales	69,837	76,470	205,778	252,177
PE Films | Personal Care Materials [Member]
Disaggregation of Revenue [Line Items]
Sales	40,958	57,356	123,770	174,985
PE Films | Surface Protection Films [Member]
Disaggregation of Revenue [Line Items]
Sales	27,052	17,193	76,194	71,926
PE Films | Films For Other Markets [Member]
Disaggregation of Revenue [Line Items]
Sales	1,827	1,921	5,814	5,266
PE Films | Film Products Subtotal [Member]
Disaggregation of Revenue [Line Items]
Sales	69,837	76,470	205,778	252,177
Flexible Packaging Films [Member] [Domain]
Disaggregation of Revenue [Line Items]
Sales	34,888	33,725	101,950	90,466
Aluminum Extrusions
Disaggregation of Revenue [Line Items]
Sales	129,506	147,661	405,310	420,455
Aluminum Extrusions | Nonresidential Building And Construction [Member]
Disaggregation of Revenue [Line Items]
Sales	64,341	75,870	202,998	213,500
Aluminum Extrusions | Consumer Durables [Member]
Disaggregation of Revenue [Line Items]
Sales	12,939	14,991	44,865	47,300
Aluminum Extrusions | Distribution [Member]
Disaggregation of Revenue [Line Items]
Sales	9,366	9,148	26,678	32,109
Aluminum Extrusions | Automotive [Member]
Disaggregation of Revenue [Line Items]
Sales	11,091	13,205	36,214	33,992
Aluminum Extrusions | Residential Building And Construction [Member]
Disaggregation of Revenue [Line Items]
Sales	11,110	11,163	33,060	32,976
Aluminum Extrusions | Aluminum Extrusions Subtotal [Member]
Disaggregation of Revenue [Line Items]
Sales	129,506	147,661	405,310	420,455
Aluminum Extrusions | Machinery and Equipment BNL [Domain]
Disaggregation of Revenue [Line Items]
Sales	10,191	11,191	29,585	30,335
Aluminum Extrusions | Electrical [Member]
Disaggregation of Revenue [Line Items]
Sales	10,468	12,093	31,910	30,243
Exports From United States [Member] | Asia [Member]
Disaggregation of Revenue [Line Items]
Sales	23,344	14,893	61,350	57,370
Exports From United States [Member] | CANADA
Disaggregation of Revenue [Line Items]
Sales	2,429	13,451	11,906	40,988
Exports From United States [Member] | Europe [Member]
Disaggregation of Revenue [Line Items]
Sales	1,616	1,608	4,493	5,127
Exports From United States [Member] | Latin America [Member]
Disaggregation of Revenue [Line Items]
Sales	3,332	3,104	8,869	9,810
Operations Outside United States [Member] | BRAZIL
Disaggregation of Revenue [Line Items]
Sales	29,481	26,591	85,202	73,402
Operations Outside United States [Member] | NETHERLANDS
Disaggregation of Revenue [Line Items]
Sales	9,471	11,428	27,508	34,750
Operations Outside United States [Member] | HUNGARY
Disaggregation of Revenue [Line Items]
Sales	6,404	7,987	18,400	25,324
Operations Outside United States [Member] | CHINA
Disaggregation of Revenue [Line Items]
Sales	0	2,376	225	6,342
Operations Outside United States [Member] | INDIA
Disaggregation of Revenue [Line Items]
Sales	$ 1,685	$ 396	$ 3,574	$ 3,216