Basis of Presentation and Significant Accounting Policies (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jul. 31, 2021	Jul. 31, 2020	Jul. 31, 2021	Jul. 31, 2020
Segment Reporting Information [Line Items]
Revenues	$ 1,543.1	$ 1,394.1	$ 4,533.0	$ 4,503.0
Management Reimbursement Revenue
Segment Reporting Information [Line Items]
Revenues	60.9	57.4	174.1	239.3
Management Reimbursement Revenue | Business & Industry
Segment Reporting Information [Line Items]
Revenues	47.5	42.6	134.1	178.0
Management Reimbursement Revenue | Aviation
Segment Reporting Information [Line Items]
Revenues	$ 13.4	$ 14.8	$ 39.9	$ 61.4