PROPERTY, PLANT AND EQUIPMENT: (Details) - USD ($) $ in Thousands	Apr. 30, 2016	Apr. 30, 2015
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 35,004	$ 39,098
Less accumulated depreciation	(23,007)	(23,335)
Property, plant and equipment, net	11,997	15,763
Land, Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	15,864	20,000
Furniture and equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 19,140	$ 19,098