Segment Information - Financial Information by Reportable Segment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2018	Apr. 30, 2017
Revenues
Revenues	$ 1,580.8	$ 1,310.5	$ 3,169.2	$ 2,637.2
Operating profit (loss)
Operating profit (loss)	45.3	51.0	64.8	74.8
Adjustment for income from unconsolidated affiliates, net, included in Aviation and Government Services	1.0	0.9	1.6	2.3
Interest expense	(13.8)	(3.0)	(28.1)	(6.3)
Income from continuing operations before income taxes	32.5	48.9	38.2	70.9
Corporate
Operating profit (loss)
Operating profit (loss)	(37.1)	(36.4)	(84.5)	(71.0)
Segment Reconciling Items
Operating profit (loss)
Adjustment for tax deductions for energy efficient government buildings, included in Technical Solutions	(2.0)	(0.8)	(2.3)	(1.4)
Adjustment for income from unconsolidated affiliates, net, included in Aviation and Government Services	(1.0)	(1.1)	(1.6)	(2.4)
Business & Industry | Operating Segments
Revenues
Revenues	723.2	637.5	1,445.3	1,293.0
Operating profit (loss)
Operating profit (loss)	43.5	36.0	72.0	63.2
Aviation | Operating Segments
Revenues
Revenues	245.4	232.1	501.6	464.0
Operating profit (loss)
Operating profit (loss)	5.1	6.8	10.9	11.4
Technology & Manufacturing | Operating Segments
Revenues
Revenues	227.5	161.4	459.5	332.9
Operating profit (loss)
Operating profit (loss)	16.0	12.1	32.9	24.8
Education | Operating Segments
Revenues
Revenues	206.3	65.2	412.6	132.2
Operating profit (loss)
Operating profit (loss)	10.6	3.6	19.8	7.2
Technical Solutions | Operating Segments
Revenues
Revenues	108.5	110.8	212.5	218.5
Operating profit (loss)
Operating profit (loss)	7.5	10.2	13.0	18.1
Healthcare | Operating Segments
Revenues
Revenues	69.9	60.6	137.6	122.3
Operating profit (loss)
Operating profit (loss)	2.7	2.4	5.4	4.9
Government Services | Operating Segments
Revenues
Revenues	0.0	42.9	0.0	74.3
Operating profit (loss)
Operating profit (loss)	$ 0.0	$ 18.2	$ (0.8)	$ 20.0