Goodwill and Other Intangible Assets - Changes in Carrying Amounts of Goodwill by Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Oct. 31, 2017		Oct. 31, 2016		Oct. 31, 2015
Goodwill [Roll Forward]
Beginning balance	$ 912.8		$ 867.5
Acquisitions	945.0	[1]	64.8	[2]
Foreign currency translation	6.4		(13.6)
Impairment loss	0.0		(6.0)		$ 0.0
Ending balance	1,864.2		912.8		867.5
Business & Industry
Goodwill [Roll Forward]
Beginning balance	470.2		463.0
Acquisitions	0.9	[1]	10.1	[2]
Foreign currency translation	2.2		(2.9)
Impairment loss			0.0
Ending balance	473.3		470.2		463.0
Aviation
Goodwill [Roll Forward]
Beginning balance	120.0		119.5
Acquisitions	3.8	[1]	1.0	[2]
Foreign currency translation	0.4		(0.6)
Impairment loss			0.0
Ending balance	124.2		120.0		119.5
Emerging Industries Group
Goodwill [Roll Forward]
Beginning balance	152.8		152.8
Acquisitions	0.0	[1]	0.0	[2]
Foreign currency translation	0.0		0.0
Impairment loss			0.0
Ending balance	152.8		152.8		152.8
Technical Solutions
Goodwill [Roll Forward]
Beginning balance	169.8		126.1
Acquisitions	6.4	[1]	53.7	[2]
Foreign currency translation	3.8		(10.1)
Impairment loss			0.0
Ending balance	180.0		169.8		126.1
GCA Services
Goodwill [Roll Forward]
Beginning balance	0.0		0.0
Acquisitions	933.9	[1]	0.0	[2]
Foreign currency translation	0.0		0.0
Impairment loss			0.0
Ending balance	933.9		0.0		0.0
Government Services
Goodwill [Roll Forward]
Beginning balance	0.0		6.0
Acquisitions	0.0	[1]	0.0	[2]
Foreign currency translation	0.0		0.0
Impairment loss			(6.0)
Ending balance	$ 0.0		$ 0.0		$ 6.0

[1] During 2017, goodwill primarily increased as a result of the GCA acquisition. See Note 4, “Acquisitions,” for additional information.

[2] During 2016, goodwill primarily increased as a result of the acquisitions of Westway and 8 Solutions. See Note 4, “Acquisitions,” for additional information.