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Property Plant and Equipment (Details) - USD ($)
12 Months Ended
Jul. 31, 2021
Jul. 31, 2020
Jul. 31, 2019
Property, Plant and Equipment [Line Items]      
Property, plant and equipment, gross $ 186,326,000 $ 171,910,000  
Less accumulated depreciation and amortization 151,040,000 144,873,000  
Property, plant and equipment, net 35,286,000 27,037,000  
Depreciation and amortization 9,343,000 10,386,000 $ 11,927,000
Machinery and equipment      
Property, Plant and Equipment [Line Items]      
Property, plant and equipment, gross 170,600,000 156,314,000  
Leasehold improvements      
Property, Plant and Equipment [Line Items]      
Property, plant and equipment, gross $ 15,726,000 $ 15,596,000