Finite-Lived Intangible Assets (Detail) - USD ($) $ in Millions	3 Months Ended
	Oct. 31, 2017	Jul. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Cost	$ 62.3	$ 62.3
Accumulated Amortization	45.3	44.0
Net	$ 17.0	18.3
Developed technologies
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Amortization Period	10 years
Cost	$ 17.7	17.7
Accumulated Amortization	14.8	14.4
Net	$ 2.9	3.3
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Amortization Period	13 years
Cost	$ 43.7	43.7
Accumulated Amortization	29.6	28.7
Net	$ 14.1	15.0
Trade names
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Amortization Period	3 years
Cost	$ 0.9	0.9
Accumulated Amortization	$ 0.9	$ 0.9