Business and segment information Geographic information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jan. 31, 2015	Jan. 31, 2014
Geographic information [Line Items]
foreign sales	0.00%	0.00%
Net sales	$ 194,857	$ 226,835
Property, plant and equipment, net of accumulated depreciation	42,020	42,541
United States
Geographic information [Line Items]
Net sales	109,257	97,311
Property, plant and equipment, net of accumulated depreciation	26,747	25,260
Middle East [Member]
Geographic information [Line Items]
Net sales	52,292	94,500
Property, plant and equipment, net of accumulated depreciation	11,608	12,751
Denmark
Geographic information [Line Items]
Property, plant and equipment, net of accumulated depreciation	3,274	4,020
Europe
Geographic information [Line Items]
Net sales	14,482	14,933
Canada
Geographic information [Line Items]
Net sales	4,160	7,591
India
Geographic information [Line Items]
Net sales	5,469	773
Property, plant and equipment, net of accumulated depreciation	391	510
Other Americas
Geographic information [Line Items]
Net sales	5,627	6,915
Other
Geographic information [Line Items]
Net sales	$ 3,570	$ 4,812