Segment Information (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2014	Jan. 31, 2013	Apr. 30, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]
Number of reportable segments	2
Revenues	$ 7,888,000	$ 10,440,000	$ 23,588,000	$ 30,423,000
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	5,400,000	6,900,000	15,900,000	20,400,000
Long-Lived Assets	19,500,000		19,500,000		21,500,000
All Other Countries [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	2,500,000	3,500,000	7,800,000	10,000,000
Long-Lived Assets	$ 0		$ 0		$ 1,000