Stock-Based Compensation Stock-Based Compensation Expenses (Details) (USD $)	12 Months Ended
	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2012
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	$ 4,263,000	$ 3,130,000	$ 3,572,000
Estimated Income tax benefit	(1,550,000)	(1,198,000)	(1,308,000)
Net stock-based compensation expense	2,713,000	1,932,000	2,264,000
Total remaining unrecognized compensation cost related to the unvested stock-based awards	8,829,000
Estimated forfeitures related to unvested stock-based awards	544,000
Weighted average number of years net compensation cost is expected to be recognized over	3 years 0 months 0 days
Stock-based compensation capitalized and included in ending inventory	68,000	72,000
Cost of Sales [Member]
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	252,000	174,000	284,000
Selling, General and Administrative Expenses [Member]
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	3,403,000	2,470,000	2,716,000
Research and Development Expense [Member]
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	608,000	486,000	572,000
Stock options [Member]
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	2,752,000	2,400,000	3,279,000
Performance Shares [Member]
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	976,000	382,000	52,000
Employee Stock Purchase Plan - ESPP [Member]
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	184,000	189,000	232,000
Discount offered to employees participating in the ESPP as a percentage of market price	15.00%
RSUs and restricted stock [Member]
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	293,000	140,000	13,000
Share units [Member]
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	41,000	24,000	12,000
Equity-classified stock-based awards [Member]
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	4,246,000	3,135,000	3,588,000
Stock appreciation rights (SARs) [Member]
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	17,000	(5,000)	(16,000)
Accrued expense related to the cash settlement of liability-classified stock appreciation rights		$ 1,000