Post Retirement Benefit Plans - Components of Net Periodic Cost for Postretirement Benefits (Detail) (Other Postretirement Benefit Plans, Defined Benefit [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Apr. 30, 2015	Apr. 30, 2014	Apr. 30, 2015	Apr. 30, 2014
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 0	$ 0	$ 0
Interest cost	0.2	0.2	0.4	0.4
Amortization of prior service cost and recognized actuarial gain	(0.4)	(0.4)	(0.8)	(0.8)
Net periodic (benefit) cost	$ (0.2)	$ (0.2)	$ (0.4)	$ (0.4)