Subsequent Events (Details) (USD $)	3 Months Ended		6 Months Ended		1 Months Ended
	Jul. 30, 2011	Jul. 31, 2010	Jul. 30, 2011	Jul. 31, 2010	Aug. 31, 2011 Dividend Declared
Subsequent Events
Cash dividend announced on common stock (in dollars per share)	$ 0.20	$ 0.16	$ 0.40	$ 0.32	$ 0.20