Valuation And Qualifying Accounts (Detail) - USD ($) $ in Millions	12 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015
Allowance for Doubtful Accounts
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at the Beginning of Period	$ 1.0	$ 1.2	$ 0.8
Charged to Costs and Expenses	0.2	0.1	0.4
Deductions	(0.4)	(0.3)
Balance at End of Period	0.8	1.0	1.2
Income Tax Valuation Allowance
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at the Beginning of Period	11.5	10.6	6.6
Charged to Costs and Expenses	16.8	0.9	4.3
Deductions			(0.3)
Balance at End of Period	$ 28.3	$ 11.5	$ 10.6