COVER PAGE - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2020	Feb. 25, 2021	Jun. 30, 2020
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Document Transition Report	false
Entity File Number	001-14989
Entity Registrant Name	WESCO International, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	25-1723342
Entity Address, Postal Zip Code	15219
Entity Address, Address Line One	225 West Station Square DriveSuite 700
Entity Address, State or Province	PA
Entity Address, City or Town	Pittsburgh,
City Area Code	412
Local Phone Number	454-2200
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
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
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 1.7
Entity Common Stock, Shares Outstanding		50,161,831
Entity Central Index Key	0000929008
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false
Common Class A [Member]
Document Information [Line Items]
Title of 12(b) Security	Common Stock, par value $.01 per share
Trading Symbol	WCC
Name of Exchange	NYSE
Series A Preferred Stock
Document Information [Line Items]
Title of 12(b) Security	Depositary Shares, each representing a 1/100th interest in a share of Series A Fixed-Rate Reset Cumulative Perpetual Preferred Stock
Trading Symbol	WCC PR A
Name of Exchange	NYSE
Preferred Share Purchase Right [Member]
Document Information [Line Items]
Title of 12(b) Security	Preferred Share Purchase Rights
Trading Symbol	N/A
Name of Exchange	NYSE