Note 4 - Revenue Recognition - Contract With Customer, Asset and Liability (Details) - USD ($) $ in Thousands	3 Months Ended
	Oct. 31, 2018	Jul. 31, 2018	Apr. 30, 2018
Beginning balance	$ 2,014	$ 1,834	$ 1,502
Costs and gross profit recognized during the period for uncompleted contracts from the prior period	(1,917)	(1,395)	(1,085)
Costs and deferred gross profit incurred on uncompleted contracts not billed at the end of the current period	2,260	1,575	1,417
Closing balance	2,357	2,014	1,834
Beginning balance	546	570	1,967
Revenue recognized during the period for uncompleted contracts from the prior period	(497)	(422)	(1,810)
New contracts entered into that are uncompleted at the end of the current period	1,550	398	413
Closing balance	$ 1,599	$ 546	$ 570