Restructuring Charges - Reconciliation of Beginning and Ending Restructuring Reserve Balances (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2018	Apr. 30, 2017
Restructuring Reserve [Roll Forward]
Beginning balance			$ 5.2
Costs incurred and charged to expense	$ 6.0	$ 5.1	10.1	$ 4.8
Costs paid or otherwise settled			(9.1)
Ending balance	6.2		6.2
Employee Separation Costs
Restructuring Reserve [Roll Forward]
Beginning balance			3.9
Costs incurred and charged to expense	5.5		8.3
Costs paid or otherwise settled			(6.7)
Ending balance	5.5		5.5
Other Costs
Restructuring Reserve [Roll Forward]
Beginning balance			1.3
Costs incurred and charged to expense	0.5		1.8
Costs paid or otherwise settled			(2.4)
Ending balance	$ 0.7		$ 0.7