Business Segments and Major Customer Information Sales to countries outside the United States (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011
Segment Reporting Information [Line Items]
Net sales	$ 406,175	$ 381,511	$ 314,708
Applied Technology [Member]
Segment Reporting Information [Line Items]
Net sales	171,778
Engineered Films [Member]
Segment Reporting Information [Line Items]
Net sales	141,976
Aerostar [Member]
Segment Reporting Information [Line Items]
Net sales	102,051
Electronic Systems [Member]
Segment Reporting Information [Line Items]
Net sales	0
Total foreign sales
Segment Reporting Information [Line Items]
Net sales	49,254	38,909	24,669
Canada
Segment Reporting Information [Line Items]
Net sales	20,640	15,237	12,694
Other foreign sales
Segment Reporting Information [Line Items]
Net sales	28,614	23,672	11,975
United States
Segment Reporting Information [Line Items]
Net sales	$ 356,921	$ 342,602	$ 290,039