Annual report pursuant to Section 13 and 15(d)

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

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Income taxes (Details) - (Provision) Benefit for income taxes were at rates different from U.S. federal statutory rates
12 Months Ended
Jul. 31, 2017
Jul. 31, 2016
Jul. 31, 2015
(Provision) Benefit 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 (14.50%) (1.10%) (18.60%)
State income taxes, net of benefit of federal tax deduction (2.10%) (0.40%) (0.50%)
Change in valuation allowance 64.00% 32.90% (15.20%)
State tax law change (82.80%)    
Other (2.00%)   0.60%
(3.40%) (2.60%) 0.30%