Business Segments and Major Customer Information Summary of net sales by principal product categories (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jan. 31, 2012	Jan. 31, 2011	Jan. 31, 2010
Segment Reporting Information [Line Items]
Net sales	$ 381,511	$ 314,708	$ 237,782
Applied Technology [Member]
Segment Reporting Information [Line Items]
Net sales	132,632	100,090	86,217
Engineered Films [Member]
Segment Reporting Information [Line Items]
Net sales	133,481	105,838	63,783
Aerostar [Member]
Segment Reporting Information [Line Items]
Net sales	52,351	48,787	27,244
Electronic Systems [Member]
Segment Reporting Information [Line Items]
Net sales	71,744	65,852	63,525
Agricultural Precision Control Devices and Accessories [Member]
Segment Reporting Information [Line Items]
Net sales	131,169	98,402	83,236
Pit Lining and Geomembrane Films [Member]
Segment Reporting Information [Line Items]
Net sales	80,154	55,048	26,834
Other Plastic Films [Member]
Segment Reporting Information [Line Items]
Net sales	53,327	50,483	36,739
Teatherd Aerostats [Member]
Segment Reporting Information [Line Items]
Net sales	17,749	22,423	3,048
Parachutes and Protective Wear [Member]
Segment Reporting Information [Line Items]
Net sales	26,069	17,375	15,732
Electronic Manufacturing Services [Member]
Segment Reporting Information [Line Items]
Net sales	63,241	60,333	60,749
Other [Member]
Segment Reporting Information [Line Items]
Net sales	$ 9,802	$ 10,644	$ 11,444