Costs and estimated earnings on uncompleted contracts Costs and estimated earnings on uncompleted contracts (Details) - USD ($) $ in Thousands	Jan. 31, 2018	Jan. 31, 2017
Costs incurred on uncompleted contracts
Costs incurred on uncompleted contracts	$ 11,955	$ 17,015
Estimated earnings	6,336	16,137
Earned revenue	18,291	33,152
Less Billings to date	18,756	32,161
Costs in excess of billings, net	(465)	991
Costs and estimated earnings in excess of billings on uncompleted contracts	1,502	2,091
Billings in excess of costs and estimated earnings on uncompleted contracts	$ (1,967)	$ (1,100)