Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Apr. 30, 2015	Apr. 30, 2014
Statement Of Financial Position [Abstract]
Short term investments (in dollars)	$ 5,272	$ 5,482
Allowance for doubtful accounts (in dollars)	$ 32	$ 39
Common stock, par value (in dollars per share)	$ 0.10	$ 0.10
Common stock, shares authorized	30,000,000	30,000,000
Common stock, shares issued	10,000,000	10,000,000
Treasury stock, shares	190,504	182,071