Shareholders' Equity (Narrative) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Jul. 31, 2012
Class of Stock [Line Items]
Acquirement minimum of outstanding common stock	15.00%
Expiration date of redeemable rights	March 2, 2016
Common stock under stock repurchase plan	16.0
Remaining authorization to repurchase under stock repurchase plan, shares	5.6
Redeemable value per each right	$ 0.001
Series A Junior Participating Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, price per one one-thousandth preferred share	$ 143.00