Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Oct. 31, 2011	Jul. 31, 2011
Stockholders' equity:
Preferred stock, par value (in dollars per share)	$ 0.1	$ 0.1
Preferred stock, shares authorized (in shares)	2,000,000	2,000,000
Preferred stock, shares issued (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.1	$ 0.1
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	28,842,543	28,731,265
Treasury stock, shares (in shares)	7,225,838	4,508,445