Shareholder Rights Plan (Details)	6 Months Ended
	Jan. 31, 2013 item
Shareholder Rights Plan
Number preferred purchase rights received for each share of common stock held	1
Threshold for activation of common stock	10.00%
Base activation threshold for existing owners	10.00%
Percent increase for activation of common stock exercises	1.00%
Common stock purchase right redeemption price	0.01