Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Apr. 30, 2013		Apr. 30, 2012
Segment Reporting Information [Line Items]
Net sales	$ 103,680		$ 117,915
Operating income	20,934		28,432
Administrative and general expenses	(4,762)		(4,160)
Applied Technology [Member]
Segment Reporting Information [Line Items]
Net sales	51,181		53,741
Operating income	19,157		22,050
Engineered Films [Member]
Segment Reporting Information [Line Items]
Net sales	34,493		41,094
Operating income	4,754		9,179
Aerostar [Member]
Segment Reporting Information [Line Items]
Net sales	21,715		25,635
Operating income	1,806		1,442
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Net sales	(3,709)	[1]	(2,555)	[1]
Operating income	(21)	[1]	(79)	[1]
Reportable Segment [Member]
Segment Reporting Information [Line Items]
Operating income	$ 25,696		$ 32,592

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