REVENUE Revenue, Performance Obligation (Details)	6 Months Ended
Jun. 30, 2018
Revenue from Contract with Customer [Abstract]
Revenue, Performance Obligation, Description of Timing	WESCO’s revenue arrangements generally consist of single performance obligations to transfer a promised good or service, or a combination of goods and services. Revenue is recognized when control has transferred to the customer, which is generally when the product has shipped from a WESCO facility or directly from a supplier. For products that ship directly from suppliers to customers, WESCO acts as the principal in the transaction and recognizes revenue on a gross basis. Revenue for integrated supply services is recognized over time based on hours incurred. This method reflects the transfer of control as the customer benefits from these services as they are being performed. WESCO generally satisfies its performance obligations within a year or less.

REVENUE Revenue, Performance Obligation (Details)

6 Months Ended

Jun. 30, 2018

Revenue from Contract with Customer [Abstract]

Revenue, Performance Obligation, Description of Timing

WESCO’s revenue arrangements generally consist of single performance obligations to transfer a promised good or service, or a combination of goods and services. Revenue is recognized when control has transferred to the customer, which is generally when the product has shipped from a WESCO facility or directly from a supplier. For products that ship directly from suppliers to customers, WESCO acts as the principal in the transaction and recognizes revenue on a gross basis. Revenue for integrated supply services is recognized over time based on hours incurred. This method reflects the transfer of control as the customer benefits from these services as they are being performed. WESCO generally satisfies its performance obligations within a year or less.