Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Oct. 31, 2013		Oct. 31, 2012		Oct. 31, 2013		Oct. 31, 2012
Segment Reporting Information [Line Items]
Net sales	$ 104,938		$ 97,011		$ 302,039		$ 316,600
Operating income	18,132		16,372		51,634		62,211
Administrative and general expenses	(4,949)		(4,451)		(14,730)		(13,258)
Applied Technology Division [Member]
Segment Reporting Information [Line Items]
Net sales	43,797		39,534		134,069		133,346
Operating income	15,149		12,289		46,176		47,248
Engineered Films Division [Member]
Segment Reporting Information [Line Items]
Net sales	40,241		33,316		111,998		111,195
Operating income	5,241		4,729		14,765		20,727
Aerostar Division [Member]
Segment Reporting Information [Line Items]
Net sales	24,269		26,385		66,706		78,865
Operating income	2,714		3,830		5,484		7,581
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Net sales	(3,369)	[1]	(2,224)	[1]	(10,734)	[1]	(6,806)	[1]
Operating income	(23)	[1]	(25)	[1]	(61)	[1]	(87)	[1]
Corporate Segment [Member]
Segment Reporting Information [Line Items]
Operating income	$ 23,081		$ 20,823		$ 66,364		$ 75,469

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