6. Property, Plant and Equipment and Leases (Details) - Schedule of Property, Plant and Equipment (USD $) In Thousands, unless otherwise specified	Apr. 30, 2013	Apr. 30, 2012
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 50,235	$ 48,350
Less, accumulated depreciation	41,919	39,976
	8,316	8,374
Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	5,477	5,500
Machinery, Equipment and Furniture [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 44,758	$ 42,850