Costs and estimated earnings on uncompleted contracts Costs and estimated earnings on uncompleted contracts (Details) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2013	Jan. 31, 2012
Costs incurred on uncompleted contracts
Costs incurred on uncompleted contracts	$ 71,382	$ 61,938
Estimated earnings	16,215	11,550
Earned revenue	87,597	73,488
Billings to date	87,234	73,091
Costs in excess of billings, net	363	397
Costs and estimated earnings in excess of billings on uncompleted contracts	1,935	2,375
Billings in excess of costs and estimated earnings on uncompleted contracts	$ (1,572)	$ (1,978)