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Insurance - Instruments Used to Collateralize Insurance Obligations (Details) - USD ($) $ in Millions | Oct. 31, 2020 | Oct. 31, 2019
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Letters Of Credit [Line Items] |  |
Instruments used to collateralize insurance obligations | $ 226.9 | $ 232.6
Standby letters of credit |  |
Letters Of Credit [Line Items] |  |
Instruments used to collateralize insurance obligations | 143.6 | 141.0
Surety bonds |  |
Letters Of Credit [Line Items] |  |
Instruments used to collateralize insurance obligations | 82.6 | 90.8
Restricted insurance deposits |  |
Letters Of Credit [Line Items] |  |
Instruments used to collateralize insurance obligations | $ 0.7 | $ 0.8

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- Definition Instruments Used To Collateralize Insurance Obligations + References No definition available. + Details
Name: | abm_InstrumentsUsedToCollateralizeInsuranceObligations
Namespace Prefix: | abm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Letters Of Credit [Line Items] + References No definition available. + Details
Name: | abm_LettersOfCreditLineItems
Namespace Prefix: | abm_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_StandbyLettersOfCreditMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_SuretyBondMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_DepositsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |