Inventories (Details) - USD ($)	Apr. 30, 2020	Jul. 31, 2019
Inventory Disclosure [Abstract]
Raw materials and components	$ 60,203,000	$ 53,959,000
Work-in-process and finished goods	38,070,000	40,576,000
Total inventories	98,273,000	94,535,000
Less reserve for excess and obsolete inventories	18,850,000	19,696,000
Inventories, net	79,423,000	74,839,000
Inventory directly related to long-term contracts	6,410,000	4,053,000
Inventory related to contracts from third party commercial customers who outsource their manufacturing to us	$ 1,606,000	$ 1,513,000