EMPLOYEE BENEFIT PLANS - Narrative (Details) $ in Millions	12 Months Ended
	Oct. 31, 2023 USD ($) plan	Oct. 31, 2022 USD ($)	Oct. 31, 2021 USD ($)
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Expected return on assets	$ 0.2	$ 0.4	$ 0.3
Net periodic benefit cost	0.6	0.1	0.3
Expected future benefit payments	$ 11.0
Number of defined contribution plans | plan	2
Cost recognized	$ 29.8	27.7	21.6
Defined Contribution Plans
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Cost recognized	59.2	54.7	21.2
Multiemployer Plans, Postretirement Benefit Plans
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Contributions by ABM	441.8	426.6	270.8
Rabbi Trust
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Fair value deferred compensation plan assets	4.0	4.1
Deferred Compensation Plans
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Total liability of deferred compensation	27.0	27.5
Compensation expense	$ 0.5	$ 0.3	$ 0.2