Acquisitions - Total Purchase Consideration for Business and Asset Acquisitions (Details) - USD ($)	Jan. 31, 2020	Oct. 31, 2019	Oct. 31, 2018
Schedule Of Business Acquisitions And Asset Acquisition, By Acquisition [Line Items]
Goodwill	$ 2,445,900,000	$ 2,428,900,000	$ 2,392,100,000
Technology
Schedule Of Business Acquisitions And Asset Acquisition, By Acquisition [Line Items]
Total identifiable intangible assets	0	12.3
Customer relationships
Schedule Of Business Acquisitions And Asset Acquisition, By Acquisition [Line Items]
Total identifiable intangible assets	3.4	7.5
Trademarks
Schedule Of Business Acquisitions And Asset Acquisition, By Acquisition [Line Items]
Total identifiable intangible assets	0	10.2
Other
Schedule Of Business Acquisitions And Asset Acquisition, By Acquisition [Line Items]
Total identifiable intangible assets	0	0.1
Acquisitions 2019
Schedule Of Business Acquisitions And Asset Acquisition, By Acquisition [Line Items]
Total identifiable intangible assets	3.4
Goodwill	4.0
Net tangible assets	1.8
Total purchase price	$ 9.2
Acquisitions 2018
Schedule Of Business Acquisitions And Asset Acquisition, By Acquisition [Line Items]
Total identifiable intangible assets		30.1
Goodwill		29.8
Net tangible assets		7.3
Total purchase price		$ 67.2