Segment Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2021	Apr. 30, 2020
Revenues
Revenues	$ 1,497.4	$ 1,496.0	$ 2,989.8	$ 3,109.0
Operating profit (loss)
Operating profit (loss)	50.3	(116.7)	160.1	(70.8)
Income from unconsolidated affiliates	0.2	0.9	0.8	1.8
Interest expense	(7.8)	(10.5)	(16.3)	(20.7)
Income (loss) from continuing operations before income taxes	42.8	(126.2)	144.6	(89.7)
Goodwill, impairment loss		163.8
Goodwill and intangible asset impairment loss	0.0	172.8	0.0	172.8
Education
Operating profit (loss)
Goodwill, impairment loss		99.3		99.3
Aviation
Operating profit (loss)
Goodwill, impairment loss		55.5
Goodwill and intangible asset impairment loss		61.1		61.1
Technical Solutions
Operating profit (loss)
Goodwill, impairment loss		9.0
Goodwill and intangible asset impairment loss		12.4		12.4
Operating Segments
Revenues
Revenues	1,530.5	1,526.4	3,055.0	3,170.0
Operating Segments | Business & Industry
Revenues
Revenues	796.2	785.6	1,605.6	1,606.5
Operating profit (loss)
Operating profit (loss)	85.3	59.2	171.0	97.4
Operating Segments | Technology & Manufacturing
Revenues
Revenues	246.3	233.7	495.5	467.6
Operating profit (loss)
Operating profit (loss)	26.9	19.7	53.8	36.3
Operating Segments | Education
Revenues
Revenues	214.2	200.1	423.6	408.0
Operating profit (loss)
Operating profit (loss)	13.6	(85.8)	35.0	(74.6)
Operating Segments | Aviation
Revenues
Revenues	148.3	184.7	291.5	423.5
Operating profit (loss)
Operating profit (loss)	5.8	(60.5)	9.0	(54.9)
Operating Segments | Technical Solutions
Revenues
Revenues	125.5	122.3	238.8	264.3
Operating profit (loss)
Operating profit (loss)	10.2	(8.4)	16.3	(0.1)
Operating Segments | Government Services
Operating profit (loss)
Operating profit (loss)	0.0	0.0	(0.1)	0.0
Elimination of inter-segment revenues
Revenues
Revenues	(33.1)	(30.4)	(65.2)	(61.0)
Corporate
Operating profit (loss)
Operating profit (loss)	(90.8)	(39.5)	(123.4)	(72.8)
Segment Reconciling Items
Operating profit (loss)
Income from unconsolidated affiliates	(0.2)	(0.9)	(0.8)	(1.8)
Adjustment for tax deductions for energy efficient government buildings, included in Technical Solutions	$ (0.4)	$ (0.4)	$ (0.6)	$ (0.4)