Share-based Compensation Expense (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2018	Apr. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense before tax	$ 2.2	$ 2.2	$ 6.1	$ 6.4
Income tax effect	(0.6)	(0.7)	(1.1)	(2.0)
Share-based compensation expense included in net income	1.6	1.5	5.0	4.4
Cost of Product Sales
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense before tax	0.1	0.1	0.3	0.3
Cost of Engineering Sales
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense before tax			0.1	0.1
Research and Product Development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense before tax	0.5	0.4	1.4	1.2
Selling and Marketing
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense before tax	0.2	0.2	0.5	1.1
General and Administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense before tax	$ 1.4	$ 1.5	$ 3.8	$ 3.7