Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jul. 31, 2013		Jul. 31, 2012		Jul. 31, 2013		Jul. 31, 2012
Segment Reporting Information [Line Items]
Net sales	$ 93,421		$ 101,674		$ 197,101		$ 219,589
Operating income	12,568		17,407		33,502		45,839
Administrative and general expenses	(5,019)		(4,647)		(9,781)		(8,807)
Applied Technology Division [Member]
Segment Reporting Information [Line Items]
Net sales	39,091		40,071		90,272		93,812
Operating income	11,870		12,909		31,027		34,959
Engineered Films Division [Member]
Segment Reporting Information [Line Items]
Net sales	37,264		36,785		71,757		77,879
Operating income	4,770		6,819		9,524		15,998
Aerostar Division [Member]
Segment Reporting Information [Line Items]
Net sales	20,722		26,845		42,437		52,480
Operating income	964		2,309		2,770		3,751
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Net sales	(3,656)	[1]	(2,027)	[1]	(7,365)	[1]	(4,582)	[1]
Operating income	(17)	[1]	17	[1]	(38)	[1]	(62)	[1]
Reportable Segment [Member]
Segment Reporting Information [Line Items]
Operating income	$ 17,587		$ 22,054		$ 43,283		$ 54,646

[1] Intersegment sales were primarily from Aerostar to Applied Technology.