Goodwill and Other Intangible Assets - Changes in Carrying Amounts of Goodwill by Segment (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Oct. 31, 2018	Oct. 31, 2018		Oct. 31, 2017
Goodwill [Roll Forward]
Beginning balance			$ 1,864.2		$ 912.8
Acquisitions	[1]				945.0
Purchase price adjustments			(6.2)
Foreign currency translation			(2.8)		6.4
Impairment loss	[2]		(20.3)
Ending balance		$ 1,834.8	1,834.8		1,864.2
Business & Industry
Goodwill [Roll Forward]
Beginning balance			529.9		404.8
Acquisitions	[1]				122.9
Purchase price adjustments			(0.9)
Foreign currency translation			(1.1)		2.2
Impairment loss	[2]		0.0
Ending balance		527.9	527.9		529.9
Aviation
Goodwill [Roll Forward]
Beginning balance			124.8		120.0
Acquisitions	[1]				4.4
Purchase price adjustments			0.4
Foreign currency translation			(0.2)		0.4
Impairment loss	[2]		0.0
Ending balance		124.9	124.9		124.8
Technology & Manufacturing
Goodwill [Roll Forward]
Beginning balance			409.3		130.7
Acquisitions	[1]				278.6
Purchase price adjustments			(2.1)
Foreign currency translation			0.0		0.0
Impairment loss	[2]		0.0
Ending balance		407.2	407.2		409.3
Education
Goodwill [Roll Forward]
Beginning balance			561.3		49.7
Acquisitions	[1]				511.6
Purchase price adjustments			(3.8)
Foreign currency translation			0.0		0.0
Impairment loss	[2]		0.0
Ending balance		557.4	557.4		561.3
Technical Solutions
Goodwill [Roll Forward]
Beginning balance			180.0		169.8
Acquisitions	[1]				6.4
Purchase price adjustments			0.4
Foreign currency translation			(1.5)		3.8
Impairment loss		(20.3)	(20.3)	[2]
Ending balance		158.7	158.7		180.0
Healthcare
Goodwill [Roll Forward]
Beginning balance			58.9		37.8
Acquisitions	[1]				21.1
Purchase price adjustments			(0.2)
Foreign currency translation			0.0		0.0
Impairment loss	[2]		0.0
Ending balance		$ 58.7	$ 58.7		$ 58.9

[1] During 2017, goodwill primarily increased as a result of the GCA acquisition. See Note 3, “Acquisitions,” for additional information.

[2] Represents accumulated impairment charges at October 31, 2018.