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COVER PAGE - shares
 3 Months Ended
Mar. 31, 2020
Apr. 30, 2020
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Mar. 31, 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  
Title of 12(b) Security Common Stock, par value $.01 per share  
Trading Symbol WCC  
Security Exchange Name NYSE  
Entity Current Reporting Status 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   41,873,053
Entity Registrant Name WESCO International, Inc.  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2020  
Document Fiscal Period Focus Q1  
Amendment Flag false  
Entity Central Index Key 0000929008