Consolidated Balance Sheets (Parentheticals) (USD $) In Thousands, except Share data, unless otherwise specified	Apr. 30, 2013	Apr. 30, 2012
Statement Of Financial Position [Abstract]
Short term investments (in dollars)	$ 6,312	$ 10,848
Allowance for doubtful accounts (in dollars)	$ 17	$ 44
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	123,572	103,619	[1]

[1] Includes 85,219 shares with a total average cost of $1,036,000 that were acquired during the former repurchase program, which was authorized in January 2011 and expired in January 2012.