Summary of Changes in Unrecognized Income Tax Benefits (Detail) - USD ($) $ in Millions	12 Months Ended
	Jul. 31, 2017	Jul. 31, 2016
Income Tax Disclosure [Abstract]
Beginning balance	$ 7.6	$ 6.0
Increases based on tax positions related to current year	0.2	1.8
Increases for tax positions of prior years	0.9	0.2
Decreases for tax positions of prior years	(1.5)
Decreases due to settlements with taxing authorities	(0.2)
Decreases due to lapse of applicable statute of limitations	(0.7)	(0.4)
Ending balance	6.3	7.6
Net interest as of end of fiscal year	$ 0.1	$ 0.4