Summary of Charges Related to Accrued Restructuring Activities (Detail) - USD ($) $ in Millions		3 Months Ended	9 Months Ended
		Apr. 30, 2018	Apr. 30, 2018
Restructuring Cost and Reserve [Line Items]
Balance at beginning period		$ 1.1	$ 2.8
Restructuring charge			0.8
Adjustments			(0.1)
Cash payments		(0.7)	(3.3)
Non-cash adjustments			0.2
Balance at end period		0.4	0.4
Employee Severance and Benefits
Restructuring Cost and Reserve [Line Items]
Balance at beginning period	[1]	0.8	2.7
Restructuring charge	[1]		0.5
Adjustments	[1]		(0.1)
Cash payments	[1]	(0.7)	(3.3)
Non-cash adjustments	[1]		0.3
Balance at end period	[1]	0.1	0.1
Facility Exit Costs
Restructuring Cost and Reserve [Line Items]
Balance at beginning period	[1]	0.3	0.1
Restructuring charge	[1]		0.3
Non-cash adjustments	[1]		(0.1)
Balance at end period	[1]	$ 0.3	$ 0.3

[1] Restructuring charges in fiscal year 2018 relate to the Fiscal Year 2017 Restructuring Plan.