Costs and estimated earnings on uncompleted contracts Costs and estimated earnings on uncompleted contracts (Details) - USD ($) $ in Thousands	Jan. 31, 2017	Jan. 31, 2016
Costs incurred on uncompleted contracts
Costs incurred on uncompleted contracts	$ 82,280	$ 78,843
Estimated earnings	51,546	46,359
Earned revenue	133,826	125,202
Less Billings to date	132,835	123,915
Costs in excess of billings, net	991	1,287
Costs and estimated earnings in excess of billings on uncompleted contracts	2,091	2,463
Billings in excess of costs and estimated earnings on uncompleted contracts	$ (1,100)	$ (1,176)