Business and segment information Geographic information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jan. 31, 2013	Jan. 31, 2012
Geographic information [Line Items]
foreign sales	0.00%	0.00%
Net sales	$ 212,018	$ 233,496
Property, plant and equipment, net of accumulated depreciation	46,401	47,842
UNITED STATES
Geographic information [Line Items]
Net sales	142,454	163,104
Property, plant and equipment, net of accumulated depreciation	27,151	30,366
Middle East [Member]
Geographic information [Line Items]
Net sales	24,631	12,721
Property, plant and equipment, net of accumulated depreciation	13,204	11,417
Europe [Member]
Geographic information [Line Items]
Net sales	19,386	20,815
Property, plant and equipment, net of accumulated depreciation	5,065	4,623
Canada
Geographic information [Line Items]
Net sales	11,183	6,894
India
Geographic information [Line Items]
Net sales	6,318	2,259
Property, plant and equipment, net of accumulated depreciation	981	1,436
Other Americas [Member]
Geographic information [Line Items]
Net sales	3,053	22,370
India
Geographic information [Line Items]
Net sales	$ 4,993	$ 5,333