Acquisitions - Total Purchase Consideration for Business and Asset Acquisitions (Details) - USD ($) $ in Millions	Jul. 31, 2019	Oct. 31, 2018	Oct. 31, 2017
Schedule Of Business Acquisitions And Asset Acquisition, By Acquisition [Line Items]
Goodwill	$ 2,391.4	$ 2,392.1	$ 2,354.8
Technology
Schedule Of Business Acquisitions And Asset Acquisition, By Acquisition [Line Items]
Total identifiable intangible assets	12.3	0.0
Customer relationships
Schedule Of Business Acquisitions And Asset Acquisition, By Acquisition [Line Items]
Total identifiable intangible assets	7.5	23.5
Trademarks
Schedule Of Business Acquisitions And Asset Acquisition, By Acquisition [Line Items]
Total identifiable intangible assets	10.2	100.0
Composite intangible asset
Schedule Of Business Acquisitions And Asset Acquisition, By Acquisition [Line Items]
Total identifiable intangible assets	0.0	1,061.9
Other
Schedule Of Business Acquisitions And Asset Acquisition, By Acquisition [Line Items]
Total identifiable intangible assets	0.1	4.2
Acquisitions 2019
Schedule Of Business Acquisitions And Asset Acquisition, By Acquisition [Line Items]
Total identifiable intangible assets	30.1
Goodwill	35.8
Net tangible assets	1.3
Total purchase price	$ 67.2
Acquisitions 2018
Schedule Of Business Acquisitions And Asset Acquisition, By Acquisition [Line Items]
Total identifiable intangible assets		1,189.6
Goodwill		70.6
Net tangible assets		59.6
Total purchase price		$ 1,319.8