Segment Information (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2013	Jan. 31, 2012	Apr. 30, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 10,440,000	$ 11,069,000	$ 30,423,000	$ 33,658,000
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	6,900,000	6,500,000	20,400,000	23,100,000
Long-Lived Assets	22,300,000		22,300,000		24,300,000
All Other Countries [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	3,500,000	4,600,000	10,000,000	10,600,000
Long-Lived Assets	$ 1,000		$ 1,000		$ 5,000