Stock-Based Compensation (Expenses) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2021	Apr. 30, 2020	Jan. 31, 2021	Oct. 31, 2020	Jul. 31, 2020
Stock-based Compensation Expenses
Stock-based compensation expense (benefit) before income tax benefit	$ 1,204,000	$ 981,000	$ 3,190,000	$ 3,098,000
Estimated Income tax benefit	(260,000)	(204,000)	(684,000)	(664,000)
Net stock-based compensation expense	944,000	777,000	2,506,000	2,434,000
Total remaining unrecognized compensation cost related to the unvested stock-based awards	11,162,000		11,162,000
Estimated forfeitures related to unvested stock-based awards	1,124,000		$ 1,124,000
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				$ 48,000
Stock options
Stock-based Compensation Expenses
Stock-based compensation expense (benefit) before income tax benefit	$ 72,000	39,000	$ 289,000	203,000
Number of stock-based awards outstanding at period end (in shares)	1,312,785		1,312,785		1,331,835	1,344,635	1,422,025
Performance shares
Stock-based Compensation Expenses
Stock-based compensation expense (benefit) before income tax benefit	$ 431,000	412,000	$ 1,096,000	1,185,000
RSUs and restricted stock
Stock-based Compensation Expenses
Stock-based compensation expense (benefit) before income tax benefit	649,000	477,000	2,270,000	1,850,000
ESPP
Stock-based Compensation Expenses
Stock-based compensation expense (benefit) before income tax benefit	52,000	53,000	$ 151,000	170,000
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	$ 0	0	$ (616,000)	(310,000)
2000 Stock Incentive Plan | Stock options
Stock-based Compensation Expenses
Number of stock-based awards outstanding at period end (in shares)	1,312,785		1,312,785
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				0
Cost of sales
Stock-based Compensation Expenses
Stock-based compensation expense (benefit) before income tax benefit	$ 42,000	45,000	$ 174,000	164,000
Selling, general and administrative expenses
Stock-based Compensation Expenses
Stock-based compensation expense (benefit) before income tax benefit	1,089,000	878,000	2,789,000	2,715,000
Research and development expenses
Stock-based Compensation Expenses
Stock-based compensation expense (benefit) before income tax benefit	$ 73,000	$ 58,000	$ 227,000	$ 219,000