Segment Reporting (Schedule Of Segment Reporting Information By Segment) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Segment Reporting Information [Line Items]
Total net sales	$ 236,121	$ 209,921	$ 470,445	$ 421,228
Add back freight	7,409	5,938	14,611	11,274
Sales as shown in the Consolidated Statements of Income	243,530	215,859	485,056	432,502
Total	22,386	14,647	43,652	30,471
Interest income	91	83	169	253
Interest expense	715	1,017	1,405	2,024
Gain on investment accounted for under fair value method			3,200	6,300
Stock option-based compensation costs	283	315	599	761
Corporate expenses, net	7,487	6,000	15,644	12,272
Income from continuing operations before income taxes	15,074	10,098	28,355	21,967
Income taxes from continuing operations	5,484	2,710	9,248	6,842
Income from continuing operations	9,590	7,388	19,107	15,125
Loss from discontinued operations	(8,300)	(35)	(13,540)	(4,774)
Net income	1,290	7,353	5,567	10,351
Intelliject [Member]
Segment Reporting Information [Line Items]
Gain on investment accounted for under fair value method	2,100	2,700	3,200	6,300
Income taxes from continuing operations	(148)	(941)	(1,235)	(1,891)
Net income	(245)	(1,507)	(1,160)	(3,046)
Film Products [Member]
Segment Reporting Information [Line Items]
Total net sales	158,266	150,226	312,651	303,925
Ongoing operations	18,727	13,441	35,734	28,907
Plant shutdowns, asset impairments, restructurings and other	(107)	(1,508)	(209)	(1,792)
Aluminum Extrusions [Member]
Segment Reporting Information [Line Items]
Total net sales	77,855	59,695	157,794	117,303
Ongoing operations	4,311	3,800	8,925	5,503
Plant shutdowns, asset impairments, restructurings and other	(545)	(1,086)	(798)	(2,147)
Alleghany And Bath County, Virginia [Member]
Segment Reporting Information [Line Items]
Unrealized loss on investment property	$ (1,018)		$ (1,018)