Earnings per Share (Details) (USD $)	1 Months Ended	2 Months Ended	3 Months Ended		9 Months Ended
	Oct. 31, 2010	Jul. 31, 2011	Aug. 31, 2011	Aug. 31, 2010	Jul. 29, 2011
Basic Earnings per Share
Net income			$ 68,638,000	$ 61,277,000
Less: net income allocated to participating unvested securities			370,000	227,000
Net income available to common shareholders			68,268,000	61,050,000
Basic weighted average common shares outstanding (in shares)			131,309,000	152,164,000
Basic earnings per share (in dollars per share)			$ 0.52	$ 0.40
Diluted Earnings per Share
Net income			68,638,000	61,277,000
Less: net income allocated to participating unvested securities			370,000	227,000
Net income available to common shareholders			68,268,000	61,050,000
Basic weighted average common shares outstanding (in shares)			131,309,000	152,164,000
Effect of dilutive securities - employee stock options (in shares)			29,000
Diluted weighted average common shares outstanding (in shares)			131,338,000	152,164,000
Diluted earnings per share (in dollars per share)			$ 0.52	$ 0.40
Options granted excluded from the computation of diluted earnings per share (in shares)			2,500,000	5,000,000
Additional amount authorized under share buyback program	500,000,000
Common stock purchased under a share buyback program (in shares)		8,100,000			15,800,000
Aggregate purchase price of common stock under a share buyback program		$ 259,500,000			$ 500,000,000
Average price of common stock purchased under a share buyback program (in dollars per share)					$ 31.70