| Cover Page | Dec. 26, 2019 |
| Cover page. | |
| Document Type | 8-K |
| Document Period End Date | Dec. 26, 2019 |
| Entity Registrant Name | WESCO International, Inc. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-14989 |
| Entity Tax Identification Number | 25-1723342 |
| 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 |
| 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 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000929008 |
| Amendment Flag | false |
