Segment Information (Narrative) (Details) (USD $)	3 Months Ended								12 Months Ended
	Apr. 30, 2013	Jan. 31, 2013	Oct. 31, 2012	Jul. 31, 2012	Apr. 30, 2012	Jan. 31, 2012	Oct. 31, 2011	Jul. 31, 2011	Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2011
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 9,770,000	$ 10,440,000	$ 10,345,000	$ 9,638,000	$ 9,811,000	$ 11,069,000	$ 11,075,000	$ 11,514,000	$ 40,193,000	$ 43,469,000	$ 46,993,000
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	6,800,000				6,300,000				27,200,000	29,400,000
Long-Lived Assets	21,500,000				24,300,000				21,500,000	24,300,000
All Other Countries [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	3,000,000				3,500,000				13,000,000	14,100,000
Long-Lived Assets	$ 1,000				$ 5,000				$ 1,000	$ 5,000