Goodwill and Other Intangible Assets - Other Intangible Assets (Details) - USD ($) $ in Millions		12 Months Ended
		Oct. 31, 2018	Oct. 31, 2016	Oct. 31, 2017
Acquired Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	[1]	$ 606.0		$ 619.2
Accumulated Amortization	[1]	(250.4)		(189.1)
Total	[1]	$ 355.7		430.1
Intangible assets weighted average life		13 years
Government Services
Acquired Indefinite-lived Intangible Assets [Line Items]
Net impairment charge			$ 4.4
Customer contracts and relationships
Acquired Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	[2]	$ 595.7		607.9
Accumulated Amortization	[2]	(243.6)		(186.3)
Total	[2]	352.2		421.6
Customer contracts and relationships | Technical Solutions
Acquired Indefinite-lived Intangible Assets [Line Items]
Net impairment charge		6.2
Reduction in carrying amount		10.5
Amortization of intangible assets		4.3
Trademarks and trade names
Acquired Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount		9.8		10.8
Accumulated Amortization		(6.4)		(2.4)
Total		3.4		8.4
Contract rights and other
Acquired Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount		0.5		0.5
Accumulated Amortization		(0.4)		(0.4)
Total		$ 0.1		$ 0.1

[1] These intangible assets are being amortized over the expected period of benefit, with a weighted average life of approximately 13 years.

[2] Reflects a net impairment charge of $6.2 million recorded in 2018, consisting of a $10.5 million reduction in the gross carrying amount of the underlying customer relationships less $4.3 million of accumulated amortization.