Fair Value of Financial Instruments - Non-Financial Assets Measured at Fair Value on a Non-Recurring Basis (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Apr. 30, 2020	Apr. 30, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill, impairment loss	$ 163.8	$ 163.8
Education
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill, impairment loss	99.3	99.3
Aviation
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill, impairment loss	55.5	55.5
Impairment of intangible assets		5.6
Impairment of intangible assets, gross		(13.8)
Impairment of intangible assets, accumulated amortization		8.2
Technical Solutions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill, impairment loss	$ 9.0	9.0
Impairment of intangible assets		3.4
Impairment of intangible assets, gross		(8.7)
Impairment of intangible assets, accumulated amortization		$ 5.3