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Auction Rate Securities - Significant Assumptions Used to Determine Fair Value of Auction Rate Securities (Details) | 12 Months Ended
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Oct. 31, 2019 | Oct. 31, 2018
Investments, Debt and Equity Securities [Abstract] |  |
Discount rates | 0.34% | 0.37%
Libor plus stated yield | 2.00% | 2.00%
Average expected lives | 4 years | 4 years

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- Definition The average expected life assumptions used to determine the fair value of auction rate securities. + References No definition available. + Details
Name: | abm_AverageExpectedLifeAuctionRateSecurities
Namespace Prefix: | abm_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition The discount rate over London Interbank Offered Rate assumptions used to determine the fair value of auction rate securities. + References No definition available. + Details
Name: | abm_SecuritiesDiscountRateOverLondonInterbankOfferedRate
Namespace Prefix: | abm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition The fixed yield over London Interbank Offered Rate used as an input in determining the fair value for the one of the Company's auction rate securities. + References No definition available. + Details
Name: | abm_SecuritiesYieldsOverLondonInterbankOfferedRate
Namespace Prefix: | abm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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