Segment Information - Financial Information by Reportable Segment (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2018	Jul. 31, 2017
Revenues
Revenues	$ 1,624.3	$ 1,318.4	$ 4,793.5	$ 3,955.6
Operating profit (loss)
Income from unconsolidated affiliates, net	1.0	1.2	2.5	3.6
Operating profit (loss)	48.1	22.6	112.9	97.4
Interest expense	(12.9)	(2.8)	(41.0)	(9.1)
Income from continuing operations before income taxes	36.1	21.0	74.4	91.9
Corporate
Operating profit (loss)
Operating profit (loss)	(42.7)	(47.5)	(127.3)	(118.5)
Segment Reconciling Items
Operating profit (loss)
Income from unconsolidated affiliates, net	(0.9)	(1.0)	(2.5)	(3.4)
Adjustment for tax deductions for energy efficient government buildings, included in Technical Solutions	(0.3)	(0.4)	(2.6)	(1.8)
Business & Industry | Operating Segments
Revenues
Revenues	735.2	652.6	2,180.5	1,945.6
Operating profit (loss)
Operating profit (loss)	38.9	37.3	111.0	100.4
Aviation | Operating Segments
Revenues
Revenues	256.8	258.9	758.3	722.9
Operating profit (loss)
Operating profit (loss)	9.7	5.4	20.6	16.8
Technology & Manufacturing | Operating Segments
Revenues
Revenues	230.8	161.5	690.3	494.4
Operating profit (loss)
Operating profit (loss)	16.9	11.0	49.8	35.8
Education | Operating Segments
Revenues
Revenues	210.9	67.3	623.5	199.5
Operating profit (loss)
Operating profit (loss)	12.0	3.9	31.8	11.1
Technical Solutions | Operating Segments
Revenues
Revenues	121.6	106.7	334.1	325.2
Operating profit (loss)
Operating profit (loss)	11.9	9.4	24.9	27.5
Healthcare | Operating Segments
Revenues
Revenues	69.1	59.3	206.7	181.6
Operating profit (loss)
Operating profit (loss)	2.5	2.8	7.9	7.7
Government Services | Operating Segments
Revenues
Revenues	0.0	12.3	0.0	86.5
Operating profit (loss)
Operating profit (loss)	$ 0.0	$ 1.7	$ (0.8)	$ 21.8