Business and segment information Geographic information (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2016	Jan. 31, 2015
Geographic information [Line Items]
foreign sales	52.00%	50.00%
Net sales	$ 122,696	$ 126,923
Property, plant and equipment, net of accumulated depreciation	25,400	24,165
United States
Geographic information [Line Items]
Net sales	58,707	64,063
Property, plant and equipment, net of accumulated depreciation	13,822	12,166
Middle East [Member]
Geographic information [Line Items]
Net sales	60,749	50,430
Property, plant and equipment, net of accumulated depreciation	11,211	11,608
Europe
Geographic information [Line Items]
Net sales	73	372
Canada
Geographic information [Line Items]
Net sales	2,581	3,248
India
Geographic information [Line Items]
Net sales	372	5,099
Property, plant and equipment, net of accumulated depreciation	367	391
Other Americas
Geographic information [Line Items]
Net sales	72	3,657
Other
Geographic information [Line Items]
Net sales	$ 142	$ 54