Amount, before tax, of (gain) loss recognized for the (reversal of write-down) write-down to fair value, less cost to sell, of a disposal group. Excludes discontinued operations.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84176398&loc=d3e2941-110230

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=68055307&loc=d3e2443-110228

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

Name:	us-gaap_DisposalGroupNotDiscontinuedOperationLossGainOnWriteDown
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Fair Value of Financial Instruments - Non-Financial Assets Measured at Fair Value on Non-Recurring Basis (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Apr. 30, 2017	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment (recovery) loss		$ (18.5)	$ 22.5	$ 0.0
Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations \| Government Services
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Offer from strategic buyer for sale of business	$ 35.0
Fair Value, Measurements, Nonrecurring \| Fair Value, Inputs, Level 3 \| Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment (recovery) loss	$ (17.4)		$ 22.5