Share-based Compensation Expenses for Continuing Operations (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jul. 31, 2012	Jul. 31, 2011	Jul. 31, 2010
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Share-based compensation expense before tax	$ 13,396	$ 9,638	$ 5,791
Cost of Sales
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Share-based compensation expense before tax	802	570	445
Cost of Engineering Sales
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Share-based compensation expense before tax	1,134
Research and Development Expense
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Share-based compensation expense before tax	2,680	3,181	1,558
Selling and Marketing Expense
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Share-based compensation expense before tax	1,686	1,110	657
General and Administrative Expense
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Share-based compensation expense before tax	$ 7,094	$ 4,777	$ 3,131