Asset Impairment Charge, Per Share, Diluted

No definition available.

Name:	abm_AssetImpairmentChargePerShareDiluted
Namespace Prefix:	abm_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Business Acquisition, Acquisition Related Costs, Per Share, Diluted

+ References

No definition available.

+ Details

Name:	abm_BusinessAcquisitionAcquisitionRelatedCostsPerShareDiluted
Namespace Prefix:	abm_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Tax Benefit Effect on Earnings Per Share, after tax

+ References

No definition available.

+ Details

Name:	abm_TaxBenefitEffectonEarningsPerShareaftertax
Namespace Prefix:	abm_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Tax Cuts And Jobs Act, Income Tax Expense (Benefit)

+ References

No definition available.

+ Details

Name:	abm_TaxCutsAndJobsActIncomeTaxExpenseBenefit
Namespace Prefix:	abm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=68055307&loc=d3e2420-110228

Reference 2: 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

+ Details

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

- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
-URI http://asc.fasb.org/extlink&oid=84229725&loc=d3e1043-128460

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_SegmentReportingInformationLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_BusinessAcquisitionAxis=abm_GCAHoldingCorp.Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Selected Quarterly Financial Data (Unaudited) - Footnote Disclosure (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended			12 Months Ended
	Oct. 31, 2018	Jan. 31, 2018	Oct. 31, 2017	Oct. 31, 2018	Oct. 31, 2017
Segment Reporting Information [Line Items]
Tax benefit, reduction resulting from enactment of the tax act		$ 22.6		$ 23.2
Tax benefit effect on diluted earnings per share (usd per share)		$ 0.34
Goodwill and intangible asset impairment	$ 26.5
Goodwill and intangible asset impairment (usd per share)	$ 0.40
GCA Holding Corp.
Segment Reporting Information [Line Items]
Transaction expenses			$ 22.0		$ 24.2
Transaction expenses per diluted share (usd per share)			$ 0.38