Segment Information (Narrative) (Details) (USD $)	3 Months Ended		6 Months Ended
	Oct. 31, 2012	Oct. 31, 2011	Oct. 31, 2012	Oct. 31, 2011	Apr. 30, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 10,345,000	$ 11,075,000	$ 19,983,000	$ 22,589,000
Contra expense			1,000,000
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	6,700,000	8,200,000	13,600,000	16,600,000
Long-Lived Assets	23,100,000		23,100,000		24,300,000
All Other Countries [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	3,600,000	2,900,000	6,400,000	6,000,000
Long-Lived Assets	$ 3,000		$ 3,000		$ 5,000