Stock-Based Compensation - Expenses (Details) - USD ($)	3 Months Ended
	Oct. 31, 2015	Oct. 31, 2014	Jul. 31, 2015
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	$ 1,051,000	$ 1,337,000
Estimated income tax benefit	(365,000)	(468,000)
Net stock-based compensation expense	686,000	869,000
Total remaining unrecognized compensation cost related to the unvested stock-based awards	10,095,000
Estimated forfeitures related to unvested stock-based awards	$ 781,000
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	$ 92,000		$ 92,000
Stock Options
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	603,000	758,000
Performance Shares
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	334,000	408,000
Employee Stock Purchase Plan - ESPP
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	$ 43,000	$ 53,000
Discount offered to employees participating in the ESPP as a percentage of market price	15.00%	15.00%
RSUs and restricted stock
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	$ 71,000	$ 104,000
Share units
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	0	14,000
Cost of sales
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	63,000	67,000
Selling, general and administrative expenses
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	874,000	1,102,000
Research and development expenses
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	$ 114,000	$ 168,000