Stock-Based Compensation (Expenses) (Details) - USD ($)	12 Months Ended
	Jul. 31, 2020	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2017
Stock-based Compensation Expenses
Stock-based compensation expense (benefit) before income tax benefit	$ 9,275,000	$ 11,427,000	$ 8,569,000
Estimated Income tax benefit	(2,042,000)	(2,553,000)	(2,005,000)
Net stock-based compensation expense	7,233,000	8,874,000	6,564,000
Total remaining unrecognized compensation cost related to the unvested stock-based awards	9,677,000
Estimated forfeitures related to unvested stock-based awards	$ 883,000
Weighted average number of years net compensation cost is expected to be recognized over	3 years 2 months 12 days
Stock-based compensation capitalized and included in ending inventory	$ 48,000	48,000
Stock options
Stock-based Compensation Expenses
Stock-based compensation expense (benefit) before income tax benefit	$ 442,000	$ 739,000	$ 1,089,000
Number of stock-based awards outstanding at period end (in shares)	1,422,025	1,555,555	1,668,975	1,855,875
Performance shares
Stock-based Compensation Expenses
Stock-based compensation expense (benefit) before income tax benefit	$ 1,491,000	$ 1,554,000	$ 1,013,000
RSUs and restricted stock
Stock-based Compensation Expenses
Stock-based compensation expense (benefit) before income tax benefit	2,543,000	2,149,000	1,458,000
ESPP
Stock-based Compensation Expenses
Stock-based compensation expense (benefit) before income tax benefit	$ 222,000	215,000	205,000
Discount offered to employees participating in the ESPP as a percentage of market price	15.00%
Share units
Stock-based Compensation Expenses
Stock-based compensation expense (benefit) before income tax benefit	$ 4,577,000	6,770,000	4,804,000
Recoupment of share units
Stock-based Compensation Expenses
Stock-based compensation expense (benefit) before income tax benefit	$ (310,000)	$ (130,000)	(62,000)
2000 Stock Incentive Plan | Stock options
Stock-based Compensation Expenses
Number of stock-based awards outstanding at period end (in shares)	1,422,025
2000 Stock Incentive Plan | Stock appreciation rights (SARs)
Stock-based Compensation Expenses
Number of stock-based awards outstanding at period end (in shares)	0	0
Cost of sales
Stock-based Compensation Expenses
Stock-based compensation expense (benefit) before income tax benefit	$ 823,000	$ 1,047,000	758,000
Selling, general and administrative expenses
Stock-based Compensation Expenses
Stock-based compensation expense (benefit) before income tax benefit	7,527,000	9,336,000	6,866,000
Research and development expenses
Stock-based Compensation Expenses
Stock-based compensation expense (benefit) before income tax benefit	$ 925,000	$ 1,044,000	$ 945,000