Share-based Compensation Expenses (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2014	Jan. 31, 2013
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Share-based compensation expense before tax	$ 3.1	$ 3.3	$ 5.8	$ 6.0
Income tax effect	(1.0)	(1.1)	(1.8)	(2.0)
Share-based compensation expense included in net income	2.1	2.2	4.0	4.0
Cost of product sales
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Share-based compensation expense before tax	0.2	0.2	0.4	0.4
Cost of Engineering Sales
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Share-based compensation expense before tax	0.1	0.3	0.2	0.7
Research and Product Development
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Share-based compensation expense before tax	0.8	0.9	1.5	1.2
Selling and Marketing
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Share-based compensation expense before tax	0.3	0.2	0.6	0.5
General and Administrative
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Share-based compensation expense before tax	$ 1.7	$ 1.7	$ 3.1	$ 3.2