Employee benefit plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2014
Employee benefit plan (Details) [Line Items]
Employer Matched Contributions Percentage Of The Employees Contribution	50.00%	50.00%	50.00%
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	10.00%	10.00%	10.00%
Share Based 401k Employer Match Expense (in Dollars)	$ 709	$ 662	$ 636
Defined Benefit Plan, Contribution in Accrued Liabilities (in Dollars)	$ 413	$ 387	$ 372
Defined Contribution Plan Minimum Annual Contribution Percent	13.00%
Minimum Age of Employee for Saving Contribution	25 years
Defined Benefit Plan Minimum Annual Investment Return Percentage	1.25%
Defined Contribution Pension Plan Expiration Date	Dec. 31, 2019
Swiss Employees [Member]
Employee benefit plan (Details) [Line Items]
Employer Matched Contributions Percentage Of The Employees Contribution	50.00%