Consolidated Condensed Balance Sheets (Parentheicals) (USD $) In Thousands, except Share data	Jul. 31, 2011	Apr. 30, 2011
Statement Of Financial Position [Abstract]
Short term investments (in dollars)	$ 6,615	$ 6,158
Allowance for doubtful accounts (in dollars)	$ 45	$ 45
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, at cost	36,819	25,119