Business and segment information Geographic information (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2017	Jan. 31, 2016
Geographic information [Line Items]
foreign sales	57.00%	50.00%
Net sales	$ 98,845	$ 122,696
Property, plant and equipment, net of accumulated depreciation	36,275	25,400
United States
Geographic information [Line Items]
Net sales	42,048	58,707
Property, plant and equipment, net of accumulated depreciation	11,747	13,822
Middle East [Member]
Geographic information [Line Items]
Net sales	28,009	60,749
Property, plant and equipment, net of accumulated depreciation	10,987	11,211
Canada
Geographic information [Line Items]
Net sales	25,915	2,581
Property, plant and equipment, net of accumulated depreciation	13,276	0
India
Geographic information [Line Items]
Net sales	2,360	372
Property, plant and equipment, net of accumulated depreciation	265	367
Other
Geographic information [Line Items]
Net sales	$ 513	$ 287