Stock-Based Compensation (Details) (USD $)	12 Months Ended
	Jul. 31, 2013	Jul. 31, 2012	Jul. 31, 2011
Income statement components of stock-based compensation expense recognized in Consolidated Statements of Income
Stock-based compensation before income taxes	$ 3,733,000	$ 3,840,000	$ 3,350,000
Income tax benefits	(1,343,000)	(1,363,000)	(1,215,000)
Total stock-based compensation expense, net of tax	2,390,000	2,477,000	2,135,000
Decrease in earnings per common share due to stock-based compensation:
Basic (in dollars per share)	$ 0.06	$ 0.06	$ 0.06
Diluted (in dollars per share)	$ 0.06	$ 0.06	$ 0.05
Cost of sales
Income statement components of stock-based compensation expense recognized in Consolidated Statements of Income
Stock-based compensation before income taxes	174,000	195,000	126,000
Operating expenses: Selling
Income statement components of stock-based compensation expense recognized in Consolidated Statements of Income
Stock-based compensation before income taxes	329,000	397,000	391,000
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	3,198,000	3,203,000	2,805,000
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	32,000	45,000	28,000
Total operating expenses
Income statement components of stock-based compensation expense recognized in Consolidated Statements of Income
Stock-based compensation before income taxes	$ 3,559,000	$ 3,645,000	$ 3,224,000