PROPERTY, PLANT AND EQUIPMENT: (Details) - USD ($) $ in Thousands	Apr. 30, 2015	Apr. 30, 2014
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 39,098	$ 39,559
Less accumulated depreciation	(23,335)	(22,337)
Property, plant and equipment, net	15,763	17,222
Land, Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	20,000	20,191
Furniture and equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 19,098	$ 19,368