Income Taxes (Tax Effects of Temporary Differences) (Details) - USD ($)	Jul. 31, 2020	Jul. 31, 2019
Deferred tax assets:
Inventory and warranty reserves	$ 5,786,000	$ 7,318,000
Compensation and commissions	3,210,000	3,548,000
Contract liabilities	0	5,331,000
Federal, state and foreign research and experimentation credits	19,656,000	18,183,000
Stock-based compensation	4,955,000	5,817,000
Foreign scientific research and experimental development expenditures	1,765,000	1,689,000
Federal, state and foreign net operating losses	3,942,000	6,248,000
Lease liabilities	7,335,000
Other	6,600,000	9,012,000
Less: valuation allowance	(11,471,000)	(12,568,000)
Total deferred tax assets	41,778,000	44,578,000
Deferred tax liabilities:
Plant and equipment	(801,000)	(1,362,000)
Lease right-of-use assets	(7,080,000)
Intangibles	(50,368,000)	(54,612,000)
Total deferred tax liabilities	(58,249,000)	(55,974,000)
Net deferred tax liabilities	$ (16,471,000)	$ (11,396,000)