Consolidated Condensed Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Nov. 30, 2011	May 31, 2011
Consolidated Condensed Balance Sheets [Abstract]
Receivables, allowance	$ 4,719	$ 4,222
Intangible assets, accumulated amortization	$ 4,144	$ 3,218
Preferred stock, shares authorized	500,000	500,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 0.3	$ 0.3
Common stock, shares authorized	30,000,000	30,000,000
Common stock, shares issued	19,765,558	19,571,138
Treasury stock	89,569	89,569