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EMPLOYEE BENEFIT PLANS - Narrative (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Feb. 12, 2024
Jun. 30, 2024
Mar. 31, 2024
Jun. 30, 2023
Jun. 30, 2024
Jun. 30, 2023
Dec. 31, 2023
Defined Benefit Plan Disclosure [Line Items]              
Defined Contribution Plan, Cost   $ 20.8   $ 21.5 $ 39.6 $ 42.9  
Pension Cost (Reversal of Cost)         5.5 0.0  
Service cost   0.5   1.2 1.0 2.4  
Interest cost   6.0   3.5 10.3 8.9  
Expected return on plan assets   (6.3)   (3.6) (10.1) (9.0)  
Recognized actuarial gain   (0.1)   (0.3) (0.2) (0.6)  
Net periodic pension cost   0.1   0.8 6.5 1.7  
Pension Cost (Reversal of Cost)         5.5 0.0  
WESCO Defined Contribution              
Defined Benefit Plan Disclosure [Line Items]              
Defined Contribution Plan, Employer Discretionary Contribution Amount   7.3          
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     3.4    
Pension Cost (Reversal of Cost)         0.0 0.0  
Service cost   0.5   1.2 1.0 2.4  
Interest cost   6.0   2.9 9.3 5.7  
Expected return on plan assets   (6.3)   (3.0) (9.8) (6.0)  
Recognized actuarial gain   (0.1)   (0.3) (0.2) (0.6)  
Net periodic pension cost   0.1   0.8 0.3 1.5  
Pension Cost (Reversal of Cost)         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)         5.5 0.0  
Service cost   0.0   0.0 0.0 0.0  
Interest cost   0.0   0.6 1.0 3.2  
Expected return on plan assets   0.0   (0.6) (0.3) (3.0)  
Recognized actuarial gain   0.0   0.0 0.0 0.0  
Net periodic pension cost   0.0   0.0 6.2 0.2  
Pension Cost (Reversal of Cost)         5.5 0.0  
Pension Plan [Member]              
Defined Benefit Plan Disclosure [Line Items]              
Other Nonoperating Gains (Losses)   (0.4)   $ (0.5) 5.5 $ (0.7)  
WESCODeferredCompensationPlanMember              
Defined Benefit Plan Disclosure [Line Items]              
Deferred Compensation Liability, Classified, Noncurrent   $ 30.3     $ 30.3   $ 27.4