COVER PAGE Document - USD ($)	12 Months Ended
	Dec. 31, 2019	Feb. 21, 2020	Jun. 30, 2019
Cover page. [Abstract]
Entity Filer Category	Large Accelerated Filer
Title of 12(b) Security	Common Stock, par value $.01 per share
Trading Symbol	WCC
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	25-1723342
Document Type	10-K
Document Transition Report	false
Document Annual Report	true
Entity Address, Address Line One	225 West Station Square DriveSuite 700
Entity Address, Postal Zip Code	15219
Entity Address, City or Town	Pittsburgh,
Entity Address, State or Province	PA
Document Period End Date	Dec. 31, 2019
Entity File Number	001-14989
Entity Registrant Name	WESCO International, Inc.
City Area Code	412
Local Phone Number	454-2200
Trading Symbol	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 2,100,000,000
Entity Common Stock, Shares Outstanding		41,873,053