Stock-Based Compensation (Details) (USD $)	3 Months Ended		9 Months Ended
	Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2013	Apr. 30, 2012
Income statement components of stock-based compensation expense recognized in Consolidated Statements of Income
Stock-based compensation before income taxes	$ 919,000	$ 706,000	$ 2,806,000	$ 3,019,000
Income tax benefits	(332,000)	(247,000)	(1,008,000)	(1,073,000)
Total stock-based compensation expense, net of tax	587,000	459,000	1,798,000	1,946,000
Decrease in earnings per common share due to stock-based compensation:
Basic (in dollars per share)	$ 0.02	$ 0.02	$ 0.07	$ 0.07
Diluted (in dollars per share)	$ 0.02	$ 0.02	$ 0.07	$ 0.07
Cost of sales
Income statement components of stock-based compensation expense recognized in Consolidated Statements of Income
Stock-based compensation before income taxes	41,000	51,000	133,000	141,000
Operating expenses: Selling
Income statement components of stock-based compensation expense recognized in Consolidated Statements of Income
Stock-based compensation before income taxes	69,000	109,000	250,000	300,000
Operating expenses: General and administrative
Income statement components of stock-based compensation expense recognized in Consolidated Statements of Income
Stock-based compensation before income taxes	802,000	533,000	2,396,000	2,545,000
Operating expenses: Research and development
Income statement components of stock-based compensation expense recognized in Consolidated Statements of Income
Stock-based compensation before income taxes	7,000	13,000	27,000	33,000
Total operating expenses
Income statement components of stock-based compensation expense recognized in Consolidated Statements of Income
Stock-based compensation before income taxes	$ 878,000	$ 655,000	$ 2,673,000	$ 2,878,000