Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Nov. 30, 2013	May 31, 2013
Statement Of Financial Position [Abstract]
Accounts receivable, allowances	$ 1,584	$ 1,272
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued
Preferred stock, shares outstanding
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	45,000,000	45,000,000
Common stock, shares issued	35,305,229	35,060,351
Common stock, shares outstanding	35,305,229	35,060,351
Treasury stock, shares	142,305	142,305