Stock-Based Compensation Expenses (Details) - USD ($)	12 Months Ended
	Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	$ 8,569,000	$ 8,506,000	$ 4,117,000
Estimated Income tax benefit	(2,005,000)	(3,065,000)	(1,434,000)
Net stock-based compensation expense	6,564,000	5,441,000	2,683,000
Total remaining unrecognized compensation cost related to the unvested stock-based awards	6,641,000
Estimated forfeitures related to unvested stock-based awards	$ 742,000
Weighted average number of years net compensation cost is expected to be recognized over	2 years 8 months 12 days
Stock-based compensation capitalized and included in ending inventory	$ 48,000	12,000
Cost of Sales
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	758,000	760,000	296,000
Selling, General and Administrative Expenses
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	6,866,000	7,071,000	3,407,000
Research and Development Expense
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	945,000	675,000	414,000
Stock options
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	$ 1,089,000	$ 1,400,000	$ 2,353,000
Number of stock-based awards outstanding at period end (in shares)	1,668,975	1,855,875	2,256,679	2,119,683
Performance Shares
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	$ 1,013,000	$ 1,607,000	$ 1,374,000
RSUs and restricted stock
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	1,458,000	829,000	227,000
Employee Stock Purchase Plan - ESPP
Stock-based Compensation Expenses
Stock-based compensation expense before income tax benefit	$ 205,000	162,000	163,000
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 before income tax benefit	$ 4,804,000	$ 4,508,000	$ 0
2000 Stock Incentive Plan | Stock options
Stock-based Compensation Expenses
Number of stock-based awards outstanding at period end (in shares)	1,668,975
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