Stockholders' Equity (Details) (USD $)	9 Months Ended
	Apr. 30, 2011
Stockholders' Equity
Maximum amount authorized by the board of directors for the repurchase of shares of the company's common stock	$ 100,000,000
Treasury Stock, Shares, Acquired	2,365,870
Treasury Stock, Value, Acquired, Cost Method	68,071,000
Average price per share of shares repurchased on the open market	$ 28.77
Amount at period end that remains to be expended under the current board repurchase authorization	$ 32,000,000
Quarterly dividend payment amount per share	$ 0.25
Dividends Declared Per Share Subsequent Event	$ 0.25
Targeted annual dividend per share	$ 1.00
Dividends Payable, Date Declared, Month and Year	2011-03
Dividends Payable, Date to be Paid, Day, Month and Year	May 20, 2011
Date Dividend Declared, subsequent period	Jun. 07, 2011