Segment and Geographic Information - Revenues by Geographic Region (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Oct. 31, 2018	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2017	Jan. 31, 2017	Oct. 31, 2018		Oct. 31, 2017		Oct. 31, 2016
Revenues
Revenues		$ 1,648.8	$ 1,624.3	$ 1,580.8	$ 1,588.3	$ 1,497.9	$ 1,318.4	$ 1,310.5	$ 1,326.7	$ 6,442.2	[1]	$ 5,453.6	[1]	$ 5,144.7	[1]
United States
Revenues
Revenues	[1]									5,997.4		5,126.8		4,845.3
All other countries
Revenues
Revenues	[1]									$ 444.8		$ 326.8		$ 299.4

[1] Substantially all of our long-lived assets are related to United States operations.