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Goodwill and Other Intangible Assets - Narrative (Details) | Oct. 31, 2020 segment
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Goodwill and Intangible Assets Disclosure [Abstract] |
Number of reporting units evaluated for impairment | 3

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- Definition Number of Reporting Units Evaluated for Impairment + References No definition available. + Details
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Namespace Prefix: | abm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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- References No definition available. + Details
Name: | us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration