Common Stock Dividends (Common Stock Dividends, Record Date And Payable Date) (Details)	3 Months Ended			6 Months Ended
	Oct. 31, 2011	Jul. 31, 2011	Apr. 30, 2011	Jul. 31, 2011
Common Stock Dividends
Dividends Payable, Date Of Record, Month, Day And Year	Aug. 12, 2011	May 13, 2011	Mar. 11, 2011	Dec. 09, 2011
Dividends Payable, Date To Be Paid, Month, Day And Year	Sep. 06, 2011	Jun. 06, 2011	Apr. 04, 2011	Jan. 03, 2012