Segment and Geographic Information - Revenues by Geographic Region (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Oct. 31, 2020	Jul. 31, 2020	Apr. 30, 2020	Jan. 31, 2020	Oct. 31, 2019	Jul. 31, 2019	Apr. 30, 2019	Jan. 31, 2019	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2018
Revenues
Revenues	$ 1,484.6	$ 1,394.1	$ 1,496.0	$ 1,612.9	$ 1,648.0	$ 1,647.9	$ 1,594.7	$ 1,607.9	$ 5,987.6	$ 6,498.6	$ 6,442.2
United States
Revenues
Revenues									5,625.1	6,025.2	5,997.4
All other countries
Revenues
Revenues									$ 362.5	$ 473.3	$ 444.8