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COVER PAGE - shares
 3 Months Ended 6 Months Ended
Jun. 30, 2020
Jun. 30, 2020
Aug. 14, 2020
Cover [Abstract]      
Document Type 10-Q    
Document Quarterly Report true    
Document Period End Date Jun. 30, 2020    
Document Transition Report false    
Entity File Number 001-14989    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 25-1723342    
Entity Address, Address Line One 225 West Station Square DriveSuite 700    
Entity Address, City or Town Pittsburgh,    
Entity Address, State or Province PA    
Entity Address, Postal Zip Code 15219    
City Area Code 412    
Local Phone Number 454-2200    
Security Exchange Name NYSE    
Entity Current Reporting Status Yes Yes  
Entity Interactive Data Current Yes    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
Entity Shell Company false    
Entity Common Stock, Shares Outstanding     50,042,547
Entity Registrant Name   WESCO International, Inc.  
Current Fiscal Year End Date   --12-31  
Document Fiscal Year Focus   2020  
Document Fiscal Period Focus   Q2  
Amendment Flag   false  
Entity Central Index Key   0000929008  
Entity Listings [Line Items]      
Security Exchange Name NYSE    
Document Period End Date Jun. 30, 2020    
Series A Preferred Stock [Member]      
Cover [Abstract]      
Title of 12(b) Security Depositary Shares, each representing a 1/1,00th interest in a share of Series A Fixed-Rate Reset Cumulative Perpetual Preferred Stock    
Trading Symbol WCC PR A    
Security Exchange Name NYSE    
Entity Listings [Line Items]      
Title of 12(b) Security Depositary Shares, each representing a 1/1,00th interest in a share of Series A Fixed-Rate Reset Cumulative Perpetual Preferred Stock    
Trading Symbol WCC PR A    
Security Exchange Name NYSE    
Preferred Share Purchase Right [Member]      
Cover [Abstract]      
Title of 12(b) Security Preferred Share Purchase Rights    
Trading Symbol N/A    
Security Exchange Name NYSE    
Entity Listings [Line Items]      
Title of 12(b) Security Preferred Share Purchase Rights    
Trading Symbol N/A    
Security Exchange Name NYSE    
Common Class A [Member]      
Cover [Abstract]      
Title of 12(b) Security Common Stock, par value $.01 per share    
Trading Symbol WCC    
Entity Listings [Line Items]      
Title of 12(b) Security Common Stock, par value $.01 per share    
Trading Symbol WCC