EMPLOYEE BENEFIT PLANS - Narrative (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
	Feb. 12, 2024	Sep. 30, 2024	Jun. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Cost		$ 18.8		$ 15.9	$ 58.4	$ 58.8
Pension Cost (Reversal of Cost)		(2.2)		0.0	3.3	0.0
Service cost		0.4		1.2	1.4	3.6
Interest cost		3.2		7.5	13.6	16.4
Expected return on plan assets		(3.2)		(7.4)	(13.3)	(16.4)
Recognized actuarial gain		(0.2)		(0.3)	(0.4)	(0.9)
Net periodic pension (benefit) cost		(2.0)		1.0	4.6	2.7
Pension Cost (Reversal of Cost)		(2.2)		0.0	3.3	0.0
Foreign Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year		7.0			7.0
Defined Benefit Plan, Plan Assets, Contributions by Employer		1.0			4.4
Pension Cost (Reversal of Cost)		0.0		0.0	0.0	0.0
Service cost		0.4		1.2	1.4	3.6
Interest cost		3.2		2.9	12.5	8.6
Expected return on plan assets		(3.2)		(3.1)	(13.0)	(9.1)
Recognized actuarial gain		(0.2)		(0.3)	(0.4)	(0.9)
Net periodic pension (benefit) cost		0.2		0.7	0.5	2.2
Pension Cost (Reversal of Cost)		0.0		0.0	0.0	0.0
UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement	$ 138.8
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Assets Transferred to (from) Plan			$ 30.6
Excise and Sales Taxes		4.8
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Settlement Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]			Other Nonoperating Income (Expense)
Pension Cost (Reversal of Cost)		(2.2)		0.0	3.3	0.0
Service cost		0.0		0.0	0.0	0.0
Interest cost		0.0		4.6	1.1	7.8
Expected return on plan assets		0.0		(4.3)	(0.3)	(7.3)
Recognized actuarial gain		0.0		0.0	0.0	0.0
Net periodic pension (benefit) cost		(2.2)		0.3	4.1	0.5
Pension Cost (Reversal of Cost)		(2.2)		0.0	3.3	0.0
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Other Nonoperating Gains (Losses)		(2.4)		$ (0.2)	3.2	$ (0.9)
WESCODeferredCompensationPlanMember
Defined Benefit Plan Disclosure [Line Items]
Deferred Compensation Liability, Classified, Noncurrent		$ 32.5			$ 32.5		$ 27.4

WESCO INTERNATIONAL INC 10-Q