Post Retirement Benefit Plans - Schedule of Plan's Change in Benefit Obligation (Detail) - Other Postretirement Benefits Plan - USD ($) $ in Millions	12 Months Ended
	Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2016
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	$ 12.6	$ 13.6
Interest cost	0.5	0.5	$ 0.5
Actuarial gain	(1.4)	(0.7)
Benefits paid	(1.0)	(0.8)
Benefit obligation at end of year	$ 10.7	$ 12.6	$ 13.6