Restructuring Charges - Reconciliation of Beginning and Ended Restructuring Reserve Balances (Detail) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2015
Restructuring Reserve [Roll Forward]
Beginning balance			$ 10.4	$ 21.3
Costs incurred and charged to expense	$ 4.0	$ 9.0	12.7	26.9	$ 40.0
Costs paid or otherwise settled			(17.9)	(37.8)
Ending balance	5.2	10.4	5.2	10.4	21.3
Employee Separation Costs
Restructuring Reserve [Roll Forward]
Beginning balance			9.2	14.7
Costs incurred and charged to expense			9.0	16.7	27.8
Costs paid or otherwise settled			(14.3)	(22.2)
Ending balance	3.9	9.2	3.9	9.2	14.7
Other Costs
Restructuring Reserve [Roll Forward]
Beginning balance			1.2	6.6
Costs incurred and charged to expense			3.7	10.2	12.2
Costs paid or otherwise settled			(3.6)	(15.6)
Ending balance	$ 1.3	$ 1.2	$ 1.3	$ 1.2	$ 6.6