Common Stock Repurchases (Details Textuals) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Oct. 31, 2011	Oct. 31, 2010	Jan. 14, 2011
Stock Repurchase [Abstract]
Additional Common stock authorized for repurchase (in shares)	20,000,000
Common stock authorized for repurchase (in shares)	49,000,000
Company repurchased common stock (in shares)	1,069,898	2,249,826
Stock repurchase price per share (in dollars per share)	$ 40.73	$ 33.65
Total Company repurchased common stock	$ 43.6	$ 75.7
Number of shares repurchased under the program	21,522,935
Number of shares available for repurchase under stock repurchase program	27,477,065
Purchase of common shares from tender offer			10,526,315
Tender price to purchase common shares (in dollars per share)			$ 38.00
Number of shares accepted for purchase under tender offer			12,172,088
Additional purchase of common shares from tender offer			1,645,773
Threshold limit for purchase of company's additional shares			2.00%
Dilutive earnings per share, impact of repurchase shares, less than (in dollars per share)	less than $0.01
Remittance by the company to the taxing authorities under statutory withholding requirements	$ 0.2	$ 4.2