Consolidated Condensed Balance Sheets (Parentheticals) (USD $) In Thousands, except Share data, unless otherwise specified	Jul. 31, 2014	Apr. 30, 2014
Statement Of Financial Position [Abstract]
Short term investments (in dollars)	$ 6,506	$ 5,482
Allowance for doubtful accounts (in dollars)	$ 31	$ 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	185,124	182,071	[1],[2],[3]

[1] Includes 18,400 shares with a total average cost of $354,000 that were acquired prior to the repurchase program authorized in January 2011.

[2] 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.

[3] Includes 19,953 shares with a total average cost of $182,000 that were acquired during the current repurchase program authorized in September 2012.