Fair Value of Financial Instruments - Narrative (Details) $ in Millions	3 Months Ended	6 Months Ended
	Apr. 30, 2020 USD ($)	Apr. 30, 2020 USD ($)	Apr. 30, 2021 reportingUnit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill reporting units | reportingUnit			3
Goodwill, impairment loss	$ 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
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
Impairment of intangible assets	3.4
Impairment of intangible assets, gross	8.7
Impairment of intangible assets, accumulated amortization	$ 5.3