Condensed Consolidated Statements of Stockholders' Equity (Parenthetical) (USD $)	3 Months Ended		6 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2013	Jan. 31, 2012
Statement of Stockholders' Equity [Abstract]
Dividends declared per common share (dollars per share)	$ 0.17	$ 0.15	$ 0.34	$ 0.30