Segment and Geographic Information - Financial Information by Reportable Segment (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]
Operating profit (loss)
Operating profit (loss)										138.6		101.9		54.7
Income from unconsolidated affiliates, net										3.2		4.2		7.6
Interest expense										(54.1)		(19.2)		(10.4)
Income from continuing operations before income taxes										87.7		86.9		51.9
Depreciation and amortization
Depreciation and amortization	[2]									112.5		70.1		57.5
Corporate
Operating profit (loss)
Operating profit (loss)										(168.8)		(189.0)		(167.2)
Depreciation and amortization
Depreciation and amortization	[2]									12.4		11.8		8.2
Segment Reconciling Items
Operating profit (loss)
Adjustment for tax deductions for energy efficient government buildings, included in Technical Solutions										(2.8)		(1.9)		(1.2)
Income from unconsolidated affiliates, net										(3.2)		(4.1)		(6.5)
Business & Industry | Operating Segments
Revenues
Revenues										2,917.6		2,629.1		2,557.1
Operating profit (loss)
Operating profit (loss)										154.6		135.6		111.6
Depreciation and amortization
Depreciation and amortization	[2]									21.3		14.5		14.4
Aviation | Operating Segments
Revenues
Revenues										1,023.8		990.4		851.5
Operating profit (loss)
Operating profit (loss)										23.2		25.3		27.7
Depreciation and amortization
Depreciation and amortization	[2]									13.1		13.4		12.2
Technology & Manufacturing | Operating Segments
Revenues
Revenues										924.5		697.4		679.3
Operating profit (loss)
Operating profit (loss)										67.4		47.8		54.8
Depreciation and amortization
Depreciation and amortization	[2]									15.6		7.0		4.2
Education | Operating Segments
Revenues
Revenues										837.5		363.1		272.1
Operating profit (loss)
Operating profit (loss)										43.8		18.0		17.4
Depreciation and amortization
Depreciation and amortization	[2]									37.1		8.4		2.1
Technical Solutions | Operating Segments
Revenues
Revenues										465.6		439.6		425.3
Operating profit (loss)
Operating profit (loss)										16.5		37.6		28.9
Depreciation and amortization
Depreciation and amortization	[2]									10.2		12.5		12.3
Healthcare | Operating Segments
Revenues
Revenues										273.3		247.5		242.7
Operating profit (loss)
Operating profit (loss)										8.8		10.6		12.7
Depreciation and amortization
Depreciation and amortization	[2]									2.8		2.3		2.5
Government Services | Operating Segments
Revenues
Revenues										0.0		86.5		116.7
Operating profit (loss)
Operating profit (loss)										(0.8)		21.8		(23.4)
Depreciation and amortization
Depreciation and amortization	[2]									$ 0.0		$ 0.0		$ 1.6

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

[2] Excludes amortization related to income from unconsolidated affiliates.