Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jul. 31, 2014		Jul. 31, 2013		Jul. 31, 2014		Jul. 31, 2013
Segment Reporting Information [Line Items]
Net sales	$ 94,485		$ 93,421		$ 196,995		$ 197,101
Operating income	10,696		12,568		27,228		33,502
Administrative and general expenses	(5,495)		(5,019)		(10,755)		(9,781)
Applied Technology Division [Member]
Segment Reporting Information [Line Items]
Net sales	36,247		39,091		82,535		90,272
Operating income	8,829		11,870		24,685		31,027
Engineered Films Division [Member]
Segment Reporting Information [Line Items]
Net sales	42,299		37,264		84,506		71,757
Operating income	5,816		4,770		11,679		9,524
Aerostar Division [Member]
Segment Reporting Information [Line Items]
Net sales	19,257		20,722		36,922		42,437
Operating income	1,628		964		1,639		2,770
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Net sales	(3,318)	[1]	(3,656)	[1]	(6,968)	[1]	(7,365)	[1]
Operating income	(82)	[1]	(17)	[1]	(20)	[1]	(38)	[1]
Corporate Segment [Member]
Segment Reporting Information [Line Items]
Operating income	$ 16,191		$ 17,587		$ 37,983		$ 43,283

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