Stock-Based Compensation - Expenses (Details) - USD ($)	3 Months Ended		9 Months Ended
	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2016	Apr. 30, 2015	Jul. 31, 2015
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	$ 1,041,000	$ 1,244,000	$ 3,166,000	$ 3,642,000
Estimated income tax benefit	(391,000)	(432,000)	(1,103,000)	(1,283,000)
Net stock-based compensation expense	650,000	812,000	2,063,000	2,359,000
Total remaining unrecognized compensation cost related to the unvested stock-based awards	7,941,000		7,941,000
Estimated forfeitures related to unvested stock-based awards	743,000		$ 743,000
Weighted average number of years net compensation cost is expected to be recognized over			2 years 10 months 24 days
Stock-based compensation capitalized and included in ending inventory	51,000		$ 51,000		$ 92,000
Stock Options
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	591,000	778,000	1,803,000	2,267,000
Performance Shares
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	369,000	308,000	1,093,000	883,000
Employee Stock Purchase Plan - ESPP
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	35,000	52,000	118,000	$ 158,000
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	46,000	106,000	152,000	$ 306,000
Share units
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	0	0	0	28,000
Cost of sales
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	70,000	71,000	233,000	204,000
Selling, general and administrative expenses
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	875,000	1,005,000	2,630,000	2,963,000
Research and development expenses
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	$ 96,000	$ 168,000	$ 303,000	$ 475,000
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%