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Employee Benefit Plans - Multiemployer Plans Additional Information (Details) - USD ($) $ in Millions | 12 Months Ended
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Oct. 31, 2020 | Oct. 31, 2019 | Oct. 31, 2018
Defined Benefit Plan Disclosure [Line Items] |  |  |
Cost recognized | $ 18.2 | $ 24.3 | $ 21.6
Multiemployer Plans, Pension Plans | Defined Contribution Plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Cost recognized | 15.5 | 9.0 | 10.6
Multiemployer Plans, Postretirement Benefit Plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Contributions by ABM | $ 264.8 | $ 269.8 | $ 263.4

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- Definition Amount of cost for defined contribution plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942 + Details
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- Definition Amount of contributions made by entity participating in defined benefit plan, defined as multiple-employer plan but accounted for as multiemployer plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 30 -Section 55 -Paragraph 64 -URI http://asc.fasb.org/extlink&oid=65881987&loc=d3e16414-114935 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 30 -Section 55 -Paragraph 63 -URI http://asc.fasb.org/extlink&oid=65881987&loc=d3e16378-114935 + Details
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