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Segment Information (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
Segment Information (Details) - USD ($) $ in Millions	Jul. 31, 2021	Jul. 31, 2020	Apr. 30, 2020	Jul. 31, 2021	Jul. 31, 2020
Revenues
Revenues	$ 1,543.1	$ 1,394.1		$ 4,533.0	$ 4,503.0
Operating (loss) profit
Operating (loss) profit	(9.4)	93.6		150.6	22.8
Income from unconsolidated affiliates	0.5	0.2		1.4	2.0
Interest expense	(6.3)	(13.8)		(22.6)	(34.5)
(Loss) income from continuing operations before income taxes	(15.2)	80.0		129.4	(9.7)
Goodwill, impairment loss			$ 163.8
Goodwill and intangible asset impairment loss	0.0	0.0		0.0	172.8
Bucio \| Settled Litigation
Operating (loss) profit
Settlement reserve	112.9			142.9
Education
Operating (loss) profit
Goodwill, impairment loss			99.3		99.3
Aviation
Operating (loss) profit
Goodwill, impairment loss			55.5
Goodwill and intangible asset impairment loss					61.1
Technical Solutions
Operating (loss) profit
Goodwill, impairment loss			$ 9.0
Goodwill and intangible asset impairment loss					12.4
Operating Segments
Revenues
Revenues	1,584.1	1,424.2		4,639.1	4,594.1
Operating Segments \| Business & Industry
Revenues
Revenues	807.7	756.9		2,413.3	2,363.4
Operating (loss) profit
Operating (loss) profit	84.7	71.6		255.6	169.1
Operating Segments \| Technology & Manufacturing
Revenues
Revenues	246.1	243.2		741.6	710.8
Operating (loss) profit
Operating (loss) profit	25.5	24.5		79.2	60.9
Operating Segments \| Education
Revenues
Revenues	208.4	188.6		632.0	596.6
Operating (loss) profit
Operating (loss) profit	17.7	18.3		52.8	(56.3)
Operating Segments \| Aviation
Revenues
Revenues	175.7	116.4		467.2	539.9
Operating (loss) profit
Operating (loss) profit	10.3	(8.2)		19.3	(63.0)
Operating Segments \| Technical Solutions
Revenues
Revenues	146.1	119.2		385.0	383.5
Operating (loss) profit
Operating (loss) profit	14.5	13.2		30.8	13.1
Operating Segments \| Government Services
Operating (loss) profit
Operating (loss) profit	0.0	0.0		(0.1)	0.0
Elimination of inter-segment revenues
Revenues
Revenues	(40.9)	(30.1)		(106.1)	(91.1)
Corporate
Operating (loss) profit
Operating (loss) profit	(161.1)	(24.8)		(284.5)	(97.7)
Segment Reconciling Items
Operating (loss) profit
Income from unconsolidated affiliates	(0.5)	(0.2)		(1.4)	(2.0)
Adjustment for tax deductions for energy efficient government buildings, included in Technical Solutions	$ (0.5)	$ (0.8)		$ (1.1)	$ (1.2)