Information on stock options outstanding - Stock-Based Compensation (Details 2) - USD ($)	12 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015
Options Outstanding	18,095	19,639	30,233
Weighted Average Exercise Price per Share	$ 31.02	$ 30	$ 50
Options Weighted Average Remaining Life (Years)	1 year 1 month 9 days
Options Aggregate Intrinsic Value	$ 69,843
Exercise Price 1
Options Range of Exercise Price	$ 1.00
Options Range of Exercise Price	$ 1.00
Options Outstanding	17,245
Weighted Average Exercise Price per Share	$ 1.00
Options Weighted Average Remaining Life (Years)	1 year 15 days
Exercise Price 640
Options Range of Exercise Price	$ 640.00
Options Range of Exercise Price	$ 640.00
Options Outstanding	850
Weighted Average Exercise Price per Share	$ 640.00
Options Weighted Average Remaining Life (Years)	2 years 7 months 10 days