Income Taxes - Changes to Deferred Tax Asset Valuation Allowance (Details) - USD ($) $ in Millions	12 Months Ended
Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2017
Operating Loss Carryforwards, Valuation Allowance Rollforward [Roll Forward]
Valuation allowance at beginning of year	$ 12.0	$ 7.7	$ 5.4
GCA acquisition	0.0	2.4	4.1
Other, net	(3.6)	1.8	(1.8)
Valuation allowance at end of year	$ 8.4	$ 12.0	$ 7.7

The portion of the valuation allowance pertaining to the deferred tax asset representing potential future taxable deductions from net operating loss carryforwards for which it is more likely than not that a tax benefit will not be realized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 30
-Paragraph 5
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=109238119&loc=d3e30536-109315

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32559-109319

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319

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