Income Taxes (Narrative) (Details) £ in Millions, $ in Millions			3 Months Ended			9 Months Ended		12 Months Ended
	Jan. 19, 2018 GBP (£)	Dec. 20, 2017 GBP (£)	Jul. 31, 2018 USD ($)	Jan. 31, 2018 USD ($)	Jul. 31, 2017	Jul. 31, 2018 USD ($)	Jul. 31, 2017	Oct. 31, 2018	Oct. 31, 2017 USD ($)
Operating Loss Carryforwards [Line Items]
Repatriation tax			$ 174.1	$ 177.9
Repatriation tax, payment periods						8 years
Transition tax rate for foreign cash and certain other net current assets				15.50%
Transition tax rate on remaining deferred foreign income				8.00%
Provisional tax expense				$ 13.2
Current state and local tax expense (benefit)			7.5	8.1
Withholding taxes relating to the unremitted foreign earnings			$ 1.9	$ 2.8		$ 1.9
Effective income tax rate			11.50%		3.80%	82.10%	4.40%
Change of provisional tax expenses related to 2017 Act			$ (5.3)			$ 196.7
Unrecognized tax benefits			65.3			65.3			$ 59.9
Unrecognized tax benefits that could be settled			$ 25.3			$ 25.3
UNITED KINGDOM
Operating Loss Carryforwards [Line Items]
Diverted profit tax | £		£ 31.0
Payment for DPT | £	£ 31.0
Scenario, Forecast
Operating Loss Carryforwards [Line Items]
Blended tax rate								23.34%