Finite-Lived Intangible Assets (Detail) - USD ($) $ in Millions	6 Months Ended
	Jan. 31, 2018	Jul. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Cost	$ 62.3	$ 62.3
Accumulated Amortization	46.6	44.0
Net	$ 15.7	18.3
Developed technologies
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Amortization Period	10 years
Cost	$ 17.7	17.7
Accumulated Amortization	15.2	14.4
Net	$ 2.5	3.3
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Amortization Period	13 years
Cost	$ 43.7	43.7
Accumulated Amortization	30.5	28.7
Net	$ 13.2	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