Consolidated Condensed Balance Sheets (Parentheicals) (USD $) In Thousands, except Share data, unless otherwise specified	Jan. 31, 2012	Apr. 30, 2011
Statement Of Financial Position [Abstract]
Short term investments (in dollars)	$ 11,733	$ 6,158
Allowance for doubtful accounts (in dollars)	$ 48	$ 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 (in shares)	103,619	25,119