Shareholders' Equity (Details 2) (USD $)	3 Months Ended
	Nov. 30, 2011	Nov. 30, 2010
Shareholders' Equity (Details 2) [Abstract]
Treasury stock reissued, shares	200,000	100,000
Aggregate share repurchase program	$ 500,000,000
Share Repurchases [Line Items]
Treasury stock purchases, cost	80,682,000	176,931,000
Amount remaining on repurchase authorization	421,800,000
Share Repurchases [Member]
Share Repurchases [Line Items]
Treasury stock purchases, shares	1,700,000	4,700,000
Treasury stock purchases, cost	78,200,000	176,500,000
Treasury stock purchases, average price per share	$ 45.84	$ 37.58
Repurchases Related To Restricted Stock Units [Member]
Share Repurchases [Line Items]
Treasury stock purchases, shares	52,000	13,000
Treasury stock purchases, cost	$ 2,400,000	$ 400,000