Costs and estimated earnings on uncompleted contracts Costs and estimated earnings on uncompleted contracts (Details) - USD ($) $ in Thousands	Jan. 31, 2016	Jan. 31, 2015
Costs incurred on uncompleted contracts
Costs incurred on uncompleted contracts	$ 78,843	$ 66,547
Estimated earnings	46,359	31,082
Earned revenue	125,202	97,629
Less Billings to date	123,915	97,610
Costs in excess of billings, net	1,287	19
Costs and estimated earnings in excess of billings on uncompleted contracts	2,463	700
Billings in excess of costs and estimated earnings on uncompleted contracts	$ (1,176)	$ (681)