Segment and Geographic Information - Financial Information by Reportable Segment (Details) - USD ($)	3 Months Ended	12 Months Ended
	Apr. 30, 2020	Oct. 31, 2021	Oct. 31, 2020	Oct. 31, 2019
Revenues
Revenues		$ 6,228,600,000	$ 5,987,600,000	$ 6,498,600,000
Operating profit
Operating profit		206,300,000	95,700,000	208,300,000
Income from unconsolidated affiliates		2,100,000	2,200,000	3,000,000.0
Interest expense		(28,600,000)	(44,600,000)	(51,100,000)
Income from continuing operations before income taxes		179,800,000	53,300,000	160,200,000
Depreciation and amortization
Depreciation and amortization		89,900,000	96,400,000	107,400,000
Goodwill, impairment loss	$ 163,800,000	0	163,800,000
Goodwill and intangible asset impairment		0	172,800,000	0
Bucio | Settled Litigation
Depreciation and amortization
Settlement reserve		142,900,000
Operating Segments
Revenues
Revenues		6,372,900,000	6,110,000,000
Elimination of inter-segment revenues
Revenues
Revenues		(144,200,000)	(122,400,000)	(127,700,000)
Corporate
Operating profit
Operating profit		(374,600,000)	(146,900,000)	(159,000,000.0)
Depreciation and amortization
Depreciation and amortization		12,700,000	13,500,000	13,900,000
Segment Reconciling Items
Operating profit
Income from unconsolidated affiliates		(2,100,000)	(2,200,000)	(3,000,000.0)
Adjustment for tax deductions for energy efficient government buildings, included in Technical Solutions		(1,200,000)	(2,100,000)	100,000
Business & Industry
Depreciation and amortization
Goodwill, impairment loss			0
Business & Industry | Operating Segments
Revenues
Revenues		3,346,500,000	3,157,800,000	3,251,400,000
Operating profit
Operating profit		337,800,000	253,700,000	182,300,000
Depreciation and amortization
Depreciation and amortization		20,400,000	18,900,000	21,300,000
Technology & Manufacturing
Depreciation and amortization
Goodwill, impairment loss			0
Technology & Manufacturing | Operating Segments
Revenues
Revenues		987,100,000	956,000,000.0	917,000,000.0
Operating profit
Operating profit		103,800,000	84,400,000	72,500,000
Depreciation and amortization
Depreciation and amortization		11,300,000	12,500,000	14,300,000
Education
Depreciation and amortization
Goodwill, impairment loss	99,300,000		99,300,000
Education | Operating Segments
Revenues
Revenues		836,400,000	808,800,000	847,400,000
Operating profit
Operating profit		60,500,000	(41,100,000)	39,000,000.0
Depreciation and amortization
Depreciation and amortization		30,600,000	33,800,000	37,300,000
Aviation
Depreciation and amortization
Goodwill, impairment loss	55,500,000		55,500,000
Goodwill and intangible asset impairment			61,100,000
Aviation | Operating Segments
Revenues
Revenues		668,800,000	680,900,000	1,017,300,000
Operating profit
Operating profit		32,500,000	(59,600,000)	21,100,000
Depreciation and amortization
Depreciation and amortization		9,100,000	10,600,000	11,900,000
Technical Solutions
Depreciation and amortization
Goodwill, impairment loss	$ 9,000,000		9,000,000.0
Goodwill and intangible asset impairment			12,400,000
Technical Solutions | Operating Segments
Revenues
Revenues		534,000,000.0	506,600,000	593,200,000
Operating profit
Operating profit		49,800,000	9,500,000	55,400,000
Depreciation and amortization
Depreciation and amortization		5,900,000	7,200,000	8,600,000
Government Services | Operating Segments
Operating profit
Operating profit		$ (200,000)	$ (100,000)	$ (100,000)