Basis of Presentation and Significant Accounting Policies - Management Reimbursement Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Oct. 31, 2021	Oct. 31, 2020	Oct. 31, 2019
Segment Reporting Information [Line Items]
Revenues	$ 6,228.6	$ 5,987.6	$ 6,498.6
Management Reimbursement Revenue
Segment Reporting Information [Line Items]
Revenues	240.3	295.6	378.7
Management Reimbursement Revenue | Business & Industry
Segment Reporting Information [Line Items]
Revenues	185.8	221.4	283.1
Management Reimbursement Revenue | Aviation
Segment Reporting Information [Line Items]
Revenues	$ 54.5	$ 74.3	$ 95.5