ACCOUNTING POLICIES	9 Months Ended
Sep. 30, 2012
Accounting Policies [Abstract]
ACCOUNTING POLICIES	ACCOUNTING POLICIES Basis of Presentation The unaudited condensed consolidated financial statements of WESCO have been prepared in accordance with Rule 10-01 of Regulation S-X of the Securities and Exchange Commission (the “SEC”). The unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto included in WESCO’s 2011 Annual Report on Form 10-K filed with the SEC. The December 31, 2011 condensed consolidated balance sheet data was derived from audited financial statements but does not include all disclosures required by accounting principles generally accepted in the United States. The unaudited condensed consolidated balance sheet as of September 30, 2012, the unaudited condensed consolidated statements of income for the three and nine months ended September 30, 2012 and 2011, respectively, and the unaudited condensed consolidated statements of cash flows for the nine months ended September 30, 2012 and 2011, respectively, in the opinion of management, have been prepared on the same basis as the audited consolidated financial statements and include all adjustments necessary for the fair statement of the results of the interim periods. All adjustments reflected in the unaudited condensed consolidated financial statements are of a normal recurring nature unless indicated. Results for the interim periods presented are not necessarily indicative of the results to be expected for the full year. Reclassification Certain prior period amounts have been reclassified to conform with the current period's financial statement presentation. Fair Value of Financial Instruments The Company measures the fair value of financial assets and liabilities based on the guidance of ASC 820, "Fair Value Measurements and Disclosures," which defines fair value, establishes a framework for measuring fair value, and expands disclosures about fair value measurements. ASC 820 establishes a fair value hierarchy, which requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. ASC 820 describes three levels of inputs that may be used to measure fair value: Level 1 inputs are quoted prices in active markets for identical assets or liabilities. Level 2 inputs include inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices in active markets for similar assets and liabilities, quoted prices for identical or similar assets or liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of assets or liabilities. Level 3 inputs are unobservable inputs in which little or no market data exists, therefore requiring an entity to develop its own assumptions. At September 30, 2012, the carrying value of WESCO’s 7.50% Senior Subordinated Notes due 2017 (the "2017 Notes") and 6.0% Convertible Senior Debentures due 2029 (the "2029 Debentures") was $494.9 million and the fair value was approximately $892.9 million. At December 31, 2011, the carrying value of WESCO’s 2017 Notes and 2029 Debentures was $495.0 million and the fair value was approximately $850.9 million. The fair value of WESCO’s 2017 Notes and 2029 Debentures is based on quoted prices in active markets and is therefore classified as Level 1 within the valuation hierarchy. The reported carrying amounts of WESCO’s other debt instruments approximate their fair values and are classified as Level 2 within the valuation hierarchy. Other debt instruments included in Level 2 are valued using a market approach, utilizing interest rates and other relevant information generated by market transactions involving similar instruments. Recent Accounting Pronouncements In July 2012, the Financial Accounting Standards Board (the "FASB"), issued updated guidance on the periodic testing of indefinite-lived intangible assets, other than goodwill, for impairment. This updated guidance will allow companies the option to first assess qualitative factors to determine if it is more-likely-than-not that an indefinite-lived intangible asset might be impaired and whether it is necessary to perform the quantitative impairment test required under current accounting standards. This guidance is effective for annual and interim impairment tests performed for fiscal years beginning after September 15, 2012. WESCO will adopt this guidance in 2013. Adoption of this guidance is not expected to have a material impact on WESCO's financial position, results of operations or cash flows.

ACCOUNTING POLICIES

Basis of Presentation

The unaudited condensed consolidated financial statements of WESCO have been prepared in accordance with Rule 10-01 of Regulation S-X of the Securities and Exchange Commission (the “SEC”). The unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto included in WESCO’s 2011 Annual Report on Form 10-K filed with the SEC. The December 31, 2011 condensed consolidated balance sheet data was derived from audited financial statements but does not include all disclosures required by accounting principles generally accepted in the United States.

The unaudited condensed consolidated balance sheet as of September 30, 2012, the unaudited condensed consolidated statements of income for the three and nine months ended September 30, 2012 and 2011, respectively, and the unaudited condensed consolidated statements of cash flows for the nine months ended September 30, 2012 and 2011, respectively, in the opinion of management, have been prepared on the same basis as the audited consolidated financial statements and include all adjustments necessary for the fair statement of the results of the interim periods. All adjustments reflected in the unaudited condensed consolidated financial statements are of a normal recurring nature unless indicated. Results for the interim periods presented are not necessarily indicative of the results to be expected for the full year.

Reclassification

Certain prior period amounts have been reclassified to conform with the current period's financial statement presentation.

Fair Value of Financial Instruments

The Company measures the fair value of financial assets and liabilities based on the guidance of ASC 820, "Fair Value Measurements and Disclosures," which defines fair value, establishes a framework for measuring fair value, and expands disclosures about fair value measurements.

ASC 820 establishes a fair value hierarchy, which requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. ASC 820 describes three levels of inputs that may be used to measure fair value:

Level 1 inputs are quoted prices in active markets for identical assets or liabilities.

Level 2 inputs include inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices in active markets for similar assets and liabilities, quoted prices for identical or similar assets or liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of assets or liabilities.

Level 3 inputs are unobservable inputs in which little or no market data exists, therefore requiring an entity to develop its own assumptions.

At September 30, 2012, the carrying value of WESCO’s 7.50% Senior Subordinated Notes due 2017 (the "2017 Notes") and 6.0% Convertible Senior Debentures due 2029 (the "2029 Debentures") was $494.9 million and the fair value was approximately $892.9 million. At December 31, 2011, the carrying value of WESCO’s 2017 Notes and 2029 Debentures was $495.0 million and the fair value was approximately $850.9 million. The fair value of WESCO’s 2017 Notes and 2029 Debentures is based on quoted prices in active markets and is therefore classified as Level 1 within the valuation hierarchy. The reported carrying amounts of WESCO’s other debt instruments approximate their fair values and are classified as Level 2 within the valuation hierarchy. Other debt instruments included in Level 2 are valued using a market approach, utilizing interest rates and other relevant information generated by market transactions involving similar instruments.

Recent Accounting Pronouncements

In July 2012, the Financial Accounting Standards Board (the "FASB"), issued updated guidance on the periodic testing of indefinite-lived intangible assets, other than goodwill, for impairment. This updated guidance will allow companies the option to first assess qualitative factors to determine if it is more-likely-than-not that an indefinite-lived intangible asset might be impaired and whether it is necessary to perform the quantitative impairment test required under current accounting standards. This guidance is effective for annual and interim impairment tests performed for fiscal years beginning after September 15, 2012. WESCO will adopt this guidance in 2013. Adoption of this guidance is not expected to have a material impact on WESCO's financial position, results of operations or cash flows.