Common Stock Repurchases (Details Textual) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2016	Jan. 31, 2015	Dec. 30, 2015	Sep. 22, 2011
Stock Repurchased and Retired During Period Cost Per Share					$ 0
Common Shares Purchased Under Tender Offer, Value					$ 325.0
Remittance to taxing authorities under statutory withholding				$ 1.1
Number of stock options exercised			100,000
Stock Repurchase Program 2011 [Member]
Additional common stock authorized for repurchase (in shares)						40,000,000
Common stock authorized for repurchase (in shares)						98,000,000
Number of shares repurchased under the program	50,518,282		50,518,282
Number of shares available for repurchase under stock repurchase program	47,481,718		47,481,718
Executive Officers and Certain Employees [Member]
Number of stock options exercised	0	0
Common Stock [Member] | Dutch Auction [Member]
Common stock authorized for repurchase (in shares)					7,317,073
Number of shares repurchased under the program					8,333,333
Maximum [Member] | Common Stock [Member] | Dutch Auction [Member]
Stock Repurchase Program, Share Offer Price					$ 41.00
Minimum [Member] | Common Stock [Member] | Dutch Auction [Member]
Stock Repurchase Program, Share Offer Price					$ 38.00