Business Segments (Schedule Of Segment Reporting Information By Segment) (Details) - USD ($) $ in Thousands		3 Months Ended											12 Months Ended
		Dec. 31, 2018		Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017		Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015
Revenue from External Customer [Line Items]
Total net sales	[1],[2]												$ 1,029,444		$ 927,647		$ 799,272
Goodwill, Impairment Loss													(46,792)		0		0
Total													41,439		(11,608)		60,323
Interest income													369		209		261
Interest expense													5,702		6,170		3,806
Gain (loss) on investment accounted for under the fair value method													30,600		33,800		1,600
Stock option-based compensation expense													1,221		264		56
Corporate expenses, net	[3]												28,893		30,879		29,607
Income (loss) before income taxes													36,368		(14,912)		27,683
Income tax expense (benefit)	[3]												11,526		(53,163)		3,217
Net income		$ 26,157		$ (34,201)	$ 14,722	$ 18,165	$ (17,929)		$ 8,274	$ 44,204	$ 3,703		24,842		38,251		24,466
Cash and cash equivalents		34,397	[1]				36,491	[1]				$ 29,511	34,397	[1]	36,491	[1]	29,511	$ 44,156
Cost of Goods and Services Sold													849,756		767,550		659,867
Sales		275,707		$ 267,294	$ 263,759	$ 258,711	245,836		$ 247,121	$ 247,347	$ 221,026		1,065,471		961,330		828,341
Foreign Country
Revenue from External Customer [Line Items]
Cash and cash equivalents		31,100					32,700						31,100		32,700
Pension Benefits
Revenue from External Customer [Line Items]
Defined benefit pension plan net liability		$ (81,873)					$ (91,769)						(81,873)		(91,769)
kaleo
Revenue from External Customer [Line Items]
Gain (loss) on investment accounted for under the fair value method	[3]												30,600		33,800		1,600
Alleghany and Bath County, Virginia
Revenue from External Customer [Line Items]
Gain (loss) on investment accounted for under the fair value method												$ 1,000	(186)		0		(1,032)
Gain (Loss) on Disposition of Assets													(38)		0		0
Unrealized Gain (Loss) on Investment Property													(186)		0		(1,032)
PE Films [Member]
Revenue from External Customer [Line Items]
Total net sales													332,488		352,459		331,146
Ongoing operations													36,181		41,546		26,312
Plant shutdowns, asset impairments, restructurings and other	[3]												(5,905)		(4,905)		(4,602)
Goodwill, Impairment Loss													(46,792)
Personal Care Materials [Member]
Revenue from External Customer [Line Items]
Goodwill, Impairment Loss													46,800		0		0
Aluminum Extrusions
Revenue from External Customer [Line Items]
Total net sales													573,126		466,833		360,098
Ongoing operations													48,613		43,454		37,794
Plant shutdowns, asset impairments, restructurings and other	[3]												(505)		321		(741)
Goodwill, Impairment Loss													0
Flexible Packaging Films [Member] [Domain]
Revenue from External Customer [Line Items]
Total net sales													123,830		108,355		108,028
Ongoing operations													9,892		(2,626)		1,774
Plant shutdowns, asset impairments, restructurings and other	[3]												(45)		(89,398)		(214)
Shipping and Handling [Member]
Revenue from External Customer [Line Items]
Other Cost of Operating Revenue													36,027
Cost of Goods and Services Sold													$ 36,027		$ 33,683		$ 29,069

[1] Information on exports and foreign operations are provided on the previous page. Cash and cash equivalents includes funds held in locations outside the U.S. of $31.1 million and $32.7 million at December 31, 2018 and 2017, respectively. Export sales relate almost entirely to PE Films. Operations outside the U.S. in The Netherlands, Hungary, China and India also relate to PE Films. Operations in Brazil are primarily related to Flexible Packaging Films, but also include PE Films operations. Sales from locations in The Netherlands and Hungary are primarily to customers located in Europe. Sales from locations in China (Guangzhou and Shanghai) are primarily to customers located in China, but also include other customers in Asia.

[2] The difference between total consolidated sales as reported in the consolidated statements of income and segment, geographic and product group net sales reported in this note is freight of $36.0 million in 2018, $33.7 million in 2017 and $29.1 million in 2016.

[3] See Notes 1, 3, 4 and 17 for more information on losses associated with plant shutdowns, asset impairments and restructurings, unusual items, gains or losses from sale of assets, gains or losses on an investment accounted for under the fair value method and other items.