Summary of Charges Related to Accrued Restructuring Activities (Parenthetical) (Detail) - USD ($) $ in Millions		12 Months Ended
		Jul. 31, 2017	Jul. 31, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring Charge	[1],[2]	$ 7.2	$ 9.6
Non-cash adjustments	[1],[2]	1.9
Cash payments	[1],[2]	(7.7)	(5.0)
Charlottesville Facility
Restructuring Cost and Reserve [Line Items]
Restructuring Charge		0.1
Fiscal Year 2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Charge		5.1
Cash payments		(2.5)
Restructuring Charge including write-off and related costs		7.2
Fiscal Year 2016 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring Charge			9.6
Cash payments		$ (5.2)	(4.4)
Fiscal Year 2014 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Cash payments			(0.2)
Fiscal Year 2013 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Cash payments			$ (0.4)

[1] Activity in fiscal year 2016 pertains to the Fiscal Year 2016 Restructuring Plan, the Fiscal Year 2014 Restructuring Plan and the 2013 Restructuring Plan. In fiscal year 2016, there were restructuring charges of $9.6 million and cash payments of ($4.4) million related to the Fiscal Year 2016 Restructuring Plan, while there were cash payments of ($0.2) million and ($0.4) million related to the Fiscal Year 2014 Restructuring Plan and Fiscal Year 2013 Restructuring Plan, respectively.

[2] Activity in fiscal year 2017 pertains to the Fiscal Year 2017 Restructuring Plan and the Fiscal Year 2016 Restructuring Plan.  In fiscal year 2017, there were restructuring charges of $7.2 million and cash payments of ($2.5) million related to the Fiscal Year 2017 Restructuring Plan, while there were cash payments of ($5.2) million related to the Fiscal Year 2016 Restructuring.