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Business Segment Information (Details 2) - Revenues [Member]
12 Months Ended
Jul. 31, 2018
Jul. 31, 2017
Jul. 31, 2016
Revenue from customers located outside of the United States [Member]      
Revenue, Major Customer [Line Items]      
Concentration risk, percentage 32.00% 31.00% 29.00%
Revenue from customers located in the United Kingdom [Member]      
Revenue, Major Customer [Line Items]      
Concentration risk, percentage 14.00% 14.00% 23.00%