Annual report pursuant to Section 13 and 15(d)

Income taxes (Details) - Benefit (provision) for income taxes were at rates different from U.S. federal statutory rates

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Income taxes (Details) - Benefit (provision) for income taxes were at rates different from U.S. federal statutory rates
12 Months Ended
Jul. 31, 2015
Jul. 31, 2014
Jul. 31, 2013
Benefit (provision) for income taxes were at rates different from U.S. federal statutory rates [Abstract]      
Federal statutory rate 34.00% 34.00% 34.00%
Penalties and other expenses not deductible for income tax return purposes (18.60%) (6.60%) (0.90%)
State income taxes, net of benefit of federal tax deduction (0.50%) 0.20% 2.50%
Change in valuation allowance (15.20%) (16.50%) (32.70%)
State tax law change   (12.30%)  
Other 0.60% 0.50% (0.90%)
0.30% (0.70%) 3.80%