Income Taxes (Narrative) (Details) £ in Millions, $ in Millions			12 Months Ended
	Jan. 19, 2018 GBP (£)	Dec. 20, 2017 GBP (£)	Oct. 31, 2018 USD ($)	Oct. 31, 2017 USD ($)	Oct. 31, 2016 USD ($)
Operating Loss Carryforwards [Line Items]
Unrecognized tax benefits			$ 68.9	$ 59.9	$ 39.9
Provisional tax expense, 2017 Act			214.6
Repatriation tax			$ 185.7
Effective tax rate (ETR)			57.90%	5.30%	7.00%
Statutory income tax rate			23.34%	35.00%
Less valuation allowance			$ 39.1	$ 59.1
Research credit			0.7	0.7	$ 1.2
Unrecognized tax benefits that would impact ETR			46.6	38.1	24.8
Interest and penalties			4.4	3.6	$ 3.7
Provisional tax expense			20.0
Deferred tax liability, undistributed foreign earnings, additional state income tax, 2017 Act			7.0
Deferred tax liability, undistributed foreign earnings, withholding taxes, 2017 Act			1.9
Deferred tax liability, undistributed foreign earnings, 2017 Act			8.9	$ 0.0
Valuation allowance, deferred tax asset, decrease			16.5
Significant change in unrecognized tax benefits that is reasonably possible during the next twelve months			26.0
UNITED KINGDOM
Operating Loss Carryforwards [Line Items]
Diverted profit tax (in GBP) | £		£ 31.0
Payment for diverted profit tax (in GBP) | £	£ 31.0
Federal [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards			53.6
California [Member]
Operating Loss Carryforwards [Line Items]
Research credit			$ 1.7