Stockholders' Equity (Details) (USD $)	12 Months Ended
	Jul. 31, 2011
Treasury Stock, Shares, Acquired	4,297,508
Treasury Stock, Value, Acquired, Cost Method	$ 121,618,000
Average price per share of shares repurchased on the open market	$ 28.30
Amount at period end that remains to be expended under the current board repurchase authorization	128,503,000
Quarterly dividend payment amount per share	$ 0.25
Dividends Declared Per Share Subsequent Event	$ 0.275
Targeted annual dividend per share	$ 1.00
Dividends Payable, Date to be Paid, Day, Month and Year	Aug. 19, 2011
Date Dividend Declared, subsequent period	Sep. 27, 2011
Targeted annual dividend per share, subsequent event	$ 1.10
First stock repurchase program [Member]
Maximum amount authorized by the board of directors for the repurchase of shares of the company's common stock	100,000,000
Second stock repurchase program [Member]
Maximum amount authorized by the board of directors for the repurchase of shares of the company's common stock	150,000,000
Maximum stock repurchase program amount as amended	$ 250,000,000