Stock-Based Compensation - Expenses (Details) - USD ($)	3 Months Ended
	Oct. 31, 2016	Oct. 31, 2015	Jul. 31, 2016
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	$ 970,000	$ 1,051,000
Estimated income tax benefit	(341,000)	(365,000)
Net stock-based compensation expense	629,000	686,000
Total remaining unrecognized compensation cost related to the unvested stock-based awards	9,738,000
Estimated forfeitures related to unvested stock-based awards	$ 788,000
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	$ 51,000		$ 51,000
Stock Options
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	$ 246,000	603,000
Number of stock-based option awards outstanding at period end (in shares)	2,138,174		2,256,679
Performance Shares
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	$ 494,000	334,000
Employee Stock Purchase Plan - ESPP
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	42,000	$ 43,000
Discount offered to employees participating in the ESPP as a percentage of market price		15.00%
RSUs and restricted stock
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	$ 188,000	$ 71,000
Stock Appreciation Rights (SARs)
Stock-based Compensation Expenses
Number of stock-based option awards outstanding at period end (in shares)	0
Cost of sales
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	$ 48,000	63,000
Selling, general and administrative expenses
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	851,000	874,000
Research and development expenses
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	$ 71,000	$ 114,000
2001 Employee Stock Purchase Plan | Employee Stock Purchase Plan - ESPP
Stock-based Compensation Expenses
Discount offered to employees participating in the ESPP as a percentage of market price	15.00%