Share-based Compensation Expense (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2018	Jan. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense before tax	$ 1.9	$ 2.6	$ 3.9	$ 4.2
Income tax effect	(0.4)	(0.8)	(0.5)	(1.3)
Share-based compensation expense included in net income	1.5	1.8	3.4	2.9
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	0.2	0.2
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	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	0.4	0.5	0.9	0.9
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	0.5	0.4	0.9
General and Administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense before tax	$ 1.1	$ 1.4	$ 2.3	$ 2.2