Segment Reporting (Schedule Of Segment Reporting Information By Segment) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Segment Reporting Information [Line Items]
Total net sales	$ 210,175	$ 196,224	$ 422,037	$ 383,749
Add back freight	5,938	4,742	11,274	8,741
Sales as shown in the Consolidated Statements of Income	216,113	200,966	433,311	392,490
Total	14,655	13,305	30,655	27,435
Interest income	83	270	253	500
Interest expense	1,017	361	2,024	716
Gain on investment accounted for under fair value method	2,700		6,300
Stock option-based compensation costs	315	516	761	1,007
Corporate expenses, net	6,065	3,178	12,417	7,034
Income from continuing operations before income taxes	10,041	9,520	22,006	19,178
Income taxes from continuing operations	2,688	3,472	6,855	6,462
Income from continuing operations	7,353	6,048	15,151	12,716
Loss from discontinued operations		(345)	(4,800)	(345)
Net income	7,353	5,703	10,351	12,371
Film Products [Member]
Segment Reporting Information [Line Items]
Total net sales	150,226	132,035	303,925	263,556
Ongoing operations	13,441	12,794	28,907	28,387
Plant shutdowns, asset impairments, restructurings and other	(1,508)	(1,084)	(1,792)	(1,084)
Aluminum Extrusions [Member]
Segment Reporting Information [Line Items]
Total net sales	59,695	63,896	117,303	119,897
Ongoing operations	3,800	1,467	5,503	238
Plant shutdowns, asset impairments, restructurings and other	(1,086)	94	(2,147)	62
Other [Member]
Segment Reporting Information [Line Items]
Total net sales	254	293	809	296
Ongoing operations	$ 8	$ 34	$ 184	$ (168)