Stockholders' Equity (Details) (USD $)	6 Months Ended
	Jan. 31, 2013	Jan. 31, 2012
Treasury stock, shares, acquired	397,798	5,066,292
Treasury stock, value, acquired, cost method	$ 10,477,000	$ 155,744,000
Average price per share of shares repurchased on the open market	$ 26.34	$ 30.74
Payment of accrued repurchases of common stock		2,001,000
Prior targeted annual dividend per share authorized by our Board of Directors		$ 1.00
Targeted annual dividend per share	$ 1.10
Remaining Authorization - Subsequent [Member]
Stock repurchase program, remaining authorized repurchase amount	45,054,000
Dividend Declared, Subsequent Event [Member]
Dividends payable, date declared, day, month and year	Mar. 07, 2013
Dividends payable, date to be paid	May 21, 2013
Quarterly dividend payment amount per share	$ 0.275
Dividends payable, date of record	Apr. 19, 2013
Dividend Declared - First [Member]
Dividends payable, date declared, day, month and year	Sep. 26, 2012
Dividends payable, date to be paid	Nov. 20, 2012
Quarterly dividend payment amount per share	$ 0.275
Dividend Declared - Second [Member]
Dividends payable, date declared, day, month and year	Dec. 06, 2012
Dividends payable, date to be paid	Dec. 27, 2012
Quarterly dividend payment amount per share	$ 0.275
Second Stock Repurchase Program [Member]
Maximum amount authorized by the Board of Directors for the repurchase of shares of the Company's common stock	250,000,000
Date Board of Directors authorized stock repurchase program	Sep. 27, 2011
Date that the stock repurchase program was completed	Feb. 06, 2013
Third Stock Repurchase Program [Member]
Maximum amount authorized by the Board of Directors for the repurchase of shares of the Company's common stock	50,000,000
Date Board of Directors authorized stock repurchase program	Dec. 06, 2012
Stock repurchase program, remaining authorized repurchase amount	$ 50,798,000