Property Plant and Equipment (Details) - USD ($)	12 Months Ended
	Jul. 31, 2020	Jul. 31, 2019	Jul. 31, 2018
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 171,910,000	$ 174,147,000
Less accumulated depreciation and amortization	144,873,000	146,121,000
Property, plant and equipment, net	27,037,000	28,026,000
Depreciation and amortization	10,386,000	11,927,000	$ 13,655,000
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	156,314,000	159,882,000
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 15,596,000	$ 14,265,000