Fair Value Measurements using Significant Unobservable Inputs (Detail) - USD ($) $ in Millions		12 Months Ended
		Jul. 31, 2017		Jul. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Balance at beginning of fiscal year		$ 15.3	[1]	$ 15.0
Actual return on plan assets
Foreign currency exchange gain		0.7		0.1
Balance at end of fiscal year	[1]	16.7		15.3
Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Balance at beginning of fiscal year		15.3	[1]	15.0
Actual return on plan assets
Relating to assets still held at end of fiscal year		0.9		0.4
Purchases, sales and settlements		(0.2)		(0.2)
Foreign currency exchange gain		0.7		0.1
Balance at end of fiscal year	[1]	$ 16.7		$ 15.3

[1] This comprises units of segregated pooled funds with an insurance company. These funds have underlying values primarily derived from mutual funds that have debt and equity securities, which are traded on an active market based on the closing price of each trading day.