WESCO International (WCC) 10-Q 6 May 16 2016 Q1 Quarterly report Financial data

DOCUMENT AND ENTITY INFORMATION

DOCUMENT AND ENTITY INFORMATION Document - shares	3 Months Ended
	Mar. 31, 2016	May. 04, 2016
Entity [Abstract]
Entity Registrant Name	WESCO INTERNATIONAL INC.
Entity Central Index Key	929,008
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		42,202,442

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Depreciation, Depletion and Amortization, Nonproduction	$ 16,374
Other Accrued Liabilities, Current	115,354	$ 102,515
Current Assets:
Cash and cash equivalents	147,834	160,279
Allowance for Doubtful Accounts Receivable, Current	22,774	22,587
Trade accounts receivable, net of allowance for doubtful accounts of $23,069 and $19,309 in 2014 and 2013, respectively	1,091,504	1,075,257
Accounts and Other Receivables, Net, Current	59,092	81,242
Inventories, net	844,106	810,067
Deferred Tax Assets, Net, Current	0	8,455
Prepaid expenses and other current assets	131,906	122,234
Total current assets	2,274,442	2,257,534
Property, buildings and equipment, net of accumulated depreciation of $229,041 and $213,758 in 2014 and 2013, respectively	167,539	166,739
Intangible assets, net	421,716	403,649
Goodwill	1,762,693	1,681,662
Other assets	64,438	60,142
Total assets	4,690,828	4,569,726
Current Liabilities:
Accounts payable	734,911	715,519
Accrued payroll and benefit costs	37,413	51,258
Short-term debt	48,251	43,314
Current portion of long-term debt	1,238	1,025
Total current liabilities	983,302	947,801
Long-term Debt, Excluding Current Maturities	1,391,227	1,439,062
Other noncurrent liabilities	54,020	44,154
Deferred income taxes	368,797	364,838
Total liabilities	$ 2,797,346	$ 2,795,855
Commitments and Contingencies
Bank Overdrafts	$ 46,135	$ 34,170
Stockholders' Equity:
Preferred stock, $.01 par value; 20,000,000 shares authorized, no shares issued or outstanding	0	0
Additional capital	1,118,869	1,117,421
Retained earnings	1,890,967	1,854,456
Treasury stock, at cost; 18,247,467 and 18,179,275 shares in 2014 and 2013, respectively	(771,760)	(772,679)
Accumulated other comprehensive income	(340,901)	(423,155)
Total WESCO International stockholders' equity	1,893,482	1,773,871
Noncontrolling interest	(4,322)	(2,801)
Total stockholders' equity	1,897,804	1,776,672
Total liabilities and stockholders' equity	4,690,828	4,569,726
Common Stock [Member]
Stockholders' Equity:
Common stock	586	586
Common Class B [Member]
Stockholders' Equity:
Common stock	$ 43	$ 43

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parentheticals) - USD ($)	Mar. 31, 2016	Dec. 31, 2015
Allowance for doubtful accounts	$ 22,774,000	$ 22,587,000
Accumulated depreciation	249,090,000	243,005,000
Finite-Lived Intangible Assets, Accumulated Amortization	151,991	138,374
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ 180,143,000	$ 182,041,000
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	20,000,000	20,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Treasury stock, shares (in shares)	20,738,340	20,763,021
Common Stock [Member]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	210,000,000	210,000,000
Common stock, shares, issued (in shares)	58,632,615	58,597,380
Common stock, shares outstanding (in shares)	42,233,706	42,173,790
Common Class B [Member]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	20,000,000	20,000,000
Common stock, shares, issued (in shares)	4,339,431	4,339,431
Common stock, shares outstanding (in shares)	0	0

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Income Statement [Abstract]
Net sales	$ 1,775,961	$ 1,816,330
Cost of goods sold	1,420,793	1,448,639
Selling, general and administrative expense	269,286	264,585
Depreciation and amortization	16,374	15,921
Income from operations	69,508	87,185
Interest expense, net	18,829	20,894
Income before income taxes	50,679	66,291
Provision for income taxes	16,145	19,498
Net income	34,534	46,793
Net (loss) income attributable to noncontrolling interest	(1,519)	(238)
Net income attributable to WESCO International, Inc.	36,053	47,031
Comprehensive Income:
Foreign currency translation adjustment	82,270	(113,814)
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	(16)	0
Comprehensive income attributable to WESCO International, Inc.	$ 118,307	$ (66,783)
Earnings per share attributable to WESCO International, Inc.
Basic (in dollars per share)	$ 0.85	$ 1.06
Diluted (in dollars per share)	$ 0.77	$ 0.90

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating Activities:
Net income	$ 34,534	$ 46,793
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	16,374	15,921
Deferred income taxes	6,473	7,849
Other operating activities, net	4,717	7,665
Changes in assets and liabilities
Increase (Decrease) in Accounts Receivable	(10,648)	(9,705)
Increase (Decrease) in Accounts and Other Receivables	(24,863)	(12,075)
Inventories, net	(17,523)	(13,248)
Prepaid expenses and other current assets	(4,597)	21,474
Accounts payable	3,223	20,589
Accrued payroll and benefit costs	(14,532)	(26,635)
Other current and noncurrent liabilities	14,388	(12,132)
Net cash provided by operating activities	78,568	90,056
Investing Activities:
Capital expenditures	(3,608)	(5,026)
Acquisition payments, net of cash acquired	(50,348)	0
Other investing activities	(8,148)	785
Net cash used in investing activities	(62,104)	(4,241)
Financing Activities:
Proceeds from issuance of short-term debt	20,776	49,360
Repayments of short-term debt	(16,645)	(43,958)
Proceeds from issuance of long-term debt	323,220	319,939
Repayments of Long-term Debt	(373,220)	(344,321)
Other financing activities, net	(209)	(484)
Net cash used in financing activities	(34,774)	(53,791)
Payments for Repurchase of Common Stock	(668)	(27,602)
Proceeds from (Repayments of) Bank Overdrafts	11,972	(6,725)
Effect of exchange rate on cash and cash equivalents	5,865	(5,992)
Net change in cash and cash equivalents	(12,445)	26,032
Cash and cash equivalents at the beginning of period	160,279	128,319
Cash and cash equivalents at the end of period	$ 147,834	$ 154,351

ORGANIZATION

ORGANIZATION	3 Months Ended
	Mar. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
ORGANIZATION	ORGANIZATION WESCO International, Inc. and its subsidiaries (collectively, “WESCO” or the "Company"), headquartered in Pittsburgh, Pennsylvania, is a full-line distributor of electrical, industrial and communications maintenance, repair and operating (“MRO”) and original equipment manufacturers (“OEM”) products, construction materials, and advanced supply chain management and logistics services used primarily in the industrial, construction, utility and commercial, institutional and government markets. WESCO serves over 80,000 active customers globally, through approximately 500 full service branches and nine distribution centers located primarily in the United States, Canada and Mexico, with operations in 14 additional countries.

ACCOUNTING POLICIES

ACCOUNTING POLICIES	3 Months Ended
	Mar. 31, 2016
Accounting Policies [Abstract]
ACCOUNTING POLICIES	ACCOUNTING POLICIES Basis of Presentation The accompanying 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 information should be read in conjunction with the audited Consolidated Financial Statements and Notes thereto included in WESCO’s 2015 Annual Report on Form 10-K as filed with the SEC on February 22, 2016. The Condensed Consolidated Balance Sheet at December 31, 2015 was derived from the audited Consolidated Financial Statements as of that date, but does not include all of the disclosures required by accounting principles generally accepted in the United States of America. The unaudited Condensed Consolidated Balance Sheet as of March 31, 2016 , the unaudited Condensed Consolidated Statements of Income and Comprehensive Income (Loss) for the three months ended March 31, 2016 and 2015 , respectively, and the unaudited Condensed Consolidated Statements of Cash Flows for the three months ended March 31, 2016 and 2015 , 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 presented herein. All adjustments reflected in the unaudited condensed consolidated financial information are of a normal recurring nature unless indicated. The results for the interim periods presented herein are not necessarily indicative of the results to be expected for the full year. During the first quarter of 2016, the Company adopted certain accounting pronouncements that were effective beginning this fiscal year. The adoption of such guidance, as described below, resulted in certain reclassifications to amounts previously reported in the Consolidated Balance Sheet at December 31, 2015 . Fair Value of Financial Instruments The Company measures the fair value of financial assets and liabilities in accordance with Financial Accounting Standards Board (FASB) Accounting Standards Codification (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 that prioritizes the inputs to valuation techniques used to measure fair value and requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to measurements involving significant unobservable inputs (Level 3 measurements). The three levels of the fair value hierarchy are as follows: • Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities that are accessible at the measurement date. • 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 March 31, 2016 , the carrying value of WESCO’s 6.0% Convertible Senior Debentures due 2029 (the "2029 Debentures") was $178.9 million and the fair value was approximately $663.9 million . At December 31, 2015 , the carrying value of WESCO’s 2029 Debentures was $177.8 million and the fair value was approximately $514.2 million . The reported carrying amounts of WESCO’s other debt instruments approximate their fair values. The Company uses a market approach to fair value all of its debt instruments, utilizing quoted prices in active markets, interest rates and other relevant information generated by market transactions involving similar instruments. Therefore, all of the Company's debt instruments are classified as Level 2 within the valuation hierarchy. For all of the Company's remaining financial instruments, consisting of cash and cash equivalents, accounts receivable, accounts payable and other accrued liabilities, carrying values are considered to approximate fair value due to the short maturity of these instruments. Recently Adopted Accounting Pronouncements In April 2015, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2015-03, Simplifying the Presentation of Debt Issuance Costs , which simplifies the presentation of debt issuance costs by requiring that debt issuance costs related to a recognized liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. The Company adopted this new guidance on a retrospective basis effective January 1, 2016. Accordingly, the Company reclassified approximately $17.7 million of debt issuance costs from other noncurrent assets to long-term debt in the balance sheet as of December 31, 2015 . In May 2015, the FASB issued ASU 2015-07, Disclosures for Investments in Certain Entities That Calculate Net Asset Value per Share (or Its Equivalent). This updated guidance removes the requirement to categorize investments for which fair value is measured using the net asset value (NAV) per share practical expedient within the fair value hierarchy. The amendments in this ASU are effective beginning in the first quarter of 2016 and will be applied retrospectively. This updated guidance will impact the Company's defined benefit plan disclosure in its Annual Report on Form 10-K for the fiscal year ending December 31, 2016 . Specifically, investments for which fair value is measured using the NAV per share practical expedient will be removed from the fair value hierarchy in all periods presented. In November 2015, the FASB issued ASU 2015-17, Balance Sheet Classification of Deferred Taxes . This ASU simplifies the presentation of deferred income taxes by requiring that all deferred tax assets and liabilities, along with any related valuation allowance, be classified as noncurrent in the balance sheet. The Company elected to early adopt this ASU on a prospective basis during the first quarter of 2016 . The adoption of this ASU did not have a material impact on WESCO's financial position and it had no impact on its results of operations or cash flows. Recently Issued Accounting Pronouncements In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers: Deferral of Effective Date . The Company previously reported that in May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers, which provides a framework for addressing revenue recognition issues and replaces almost all existing revenue recognition guidance in current U.S. generally accepted accounting principles. The core principle of ASU 2014-09 is for companies to recognize revenue for the transfer of goods or services to customers in amounts that reflect the consideration to which the company expects to be entitled in exchange for those goods or services. ASU 2014-09 will also result in enhanced disclosures about revenue, provide guidance for transactions that were not previously addressed comprehensively, and improve guidance for multiple-element arrangements. The amendments in ASU 2015-14 defer the effective date of the new revenue recognition guidance to annual reporting periods beginning after December 15, 2017, including interim periods within that reporting period. Early adoption is permitted to the original effective date of December 15, 2016, including interim periods within that reporting period. Management is currently evaluating the future impact of this guidance on WESCO's consolidated financial statements and notes thereto. In February 2016, the FASB issued ASU 2016-02, Leases , a comprehensive new standard that amends various aspects of existing accounting guidance for leases, including the recognition of a right-of-use asset and a lease liability on the balance sheet and disclosing key information about leasing arrangements. This guidance is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Early adoption is permitted. The new leasing standard requires modified retrospective transition, which requires application of the new guidance at the beginning of the earliest comparative period presented in the year of adoption. Management is currently evaluating the impact of this new standard on WESCO's consolidated financial statements and notes thereto. In March 2016 and April 2016, the FASB issued ASU 2016-08, Principal versus Agent Considerations (Reporting Revenue Gross versus Net) , and ASU 2016-10, Identifying Performance Obligations and Licensing , respectively. The amendments in these ASUs clarify the implementation guidance on principal versus agent considerations and identifying performance obligations, respectively. Neither ASU changed the core principle in the revenue recognition standard outlined above. These ASUs apply to all entities that enter into contracts with customers to transfer goods or services (that are an output of the entity’s ordinary activities) in exchange for consideration. The effective dates and transition requirements for these ASUs are the same as the effective dates and transition requirements of the revenue recognition guidance outlined above. Management is currently evaluating the impact of these ASUs on WESCO's consolidated financial statements and notes thereto. In March 2016, the FASB issued ASU 2016-09, Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting , which simplifies several aspects of accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. The amendments in this ASU affect all entities that issue share-based payment awards to their employees. Management is currently evaluating the impact of this accounting standard on WESCO's consolidated financial statements and notes thereto. Other pronouncements issued by the FASB or other authoritative accounting standards groups with future effective dates are either not applicable or are not expected to be significant to WESCO’s financial position, results of operations or cash flows.

ACQUISITIONS

ACQUISITIONS	3 Months Ended
	Mar. 31, 2016
Business Combinations [Abstract]
ACQUISITIONS	ACQUISITIONS The following table sets forth the consideration paid for acquisitions: Three Months Ended (In thousands of dollars) March 31, Fair value of assets acquired $ 77,005 Fair value of liabilities assumed 25,005 Cash paid for acquisitions $ 52,000 Supplemental cash flow disclosure: Cash paid for acquisitions $ 52,000 Less: cash acquired (1,652 ) Cash paid for acquisitions, net of cash acquired $ 50,348 The fair values of assets acquired and liabilities assumed during the three months ended March 31, 2016 are based upon preliminary calculations and valuations. WESCO's estimates and assumptions for its preliminary purchase price allocation are subject to change as it obtains additional information for its estimates during the respective measurement period (up to one year from the respective acquisition date). Acquisition of Atlanta Electrical Distributors, LLC On March 14, 2016 , WESCO Distribution, Inc. completed the acquisition of Atlanta Electrical Distributors, LLC ("AED") , an Atlanta-based electrical distributor focused on the construction and MRO markets from five locations in Georgia with approximately $85 million in annual sales. WESCO funded the purchase price paid at closing with borrowings under its revolving credit facility. The purchase price was allocated to the respective assets and liabilities based upon their estimated fair values as of the acquisition date. In addition to the cash paid at closing, the purchase price includes a contingent payment that may be earned upon the achievement of certain financial performance targets over three consecutive one year periods. The fair value of the contingent consideration was determined using a probability-weighted outcome analysis and Level 3 inputs such as internal forecasts. This amount has been accrued at the maximum potential payout under the terms of the purchase agreement and it is included in the fair value of liabilities assumed as presented above. The preliminary fair value of intangibles was estimated by management and the allocation resulted in intangible assets of $13.7 million and goodwill of $41.1 million . Management believes that the majority of goodwill is deductible for tax purposes. 2015 Acquisitions of Needham Electric Supply Corporation and Hill Country Electric Supply, LP On October 30, 2015 , WESCO Distribution, Inc. completed the acquisition of Needham Electric Supply Corporation , an electrical distributor focused on the commercial construction and lighting national account markets from 24 locations in Massachusetts, New Hampshire and Vermont with approximately $115 million in annual sales. WESCO funded the purchase price paid at closing with cash and borrowings under its Revolving Credit Facility. The purchase price was allocated to the respective assets and liabilities based upon their estimated fair values as of the acquisition date. The fair value of intangibles was estimated by management and the allocation resulted in intangible assets of $31.0 million and goodwill of $35.7 million . The intangible assets include customer relationships of $24.5 million amortized over 12 and 14 years, and trademarks of $6.5 million amortized over 13 years. No residual value is estimated for the intangible assets being amortized. Management believes that the majority of goodwill is deductible for tax purposes. On May 1, 2015 , WESCO Distribution, Inc. completed the acquisition of Hill Country Electric Supply, LP , an electrical distributor focused on the commercial construction market from nine locations in Central and South Texas with approximately $140 million in annual sales. WESCO funded the purchase price paid at closing with borrowings under its prior revolving credit facility. The purchase price was allocated to the respective assets and liabilities based upon their estimated fair values as of the acquisition date. The fair value of intangibles was estimated by management and the allocation resulted in intangible assets of $21.1 million and goodwill of $15.8 million . The intangible assets include customer relationships of $13.1 million amortized over 11 years, non-compete agreements of $0.2 million amortized over 5 years, and trademarks of $7.8 million amortized over 12 years. No residual value is estimated for the intangible assets being amortized. Management believes that the majority of goodwill is deductible for tax purposes.

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	3 Months Ended
	Mar. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
STOCK-BASED COMPENSATION	STOCK-BASED COMPENSATION WESCO’s stock-based employee compensation plans are comprised of stock-settled stock appreciation rights, restricted stock units and performance-based awards. Compensation cost for all stock-based awards is measured at fair value on the date of grant and compensation cost is recognized, net of estimated forfeitures, over the service period for awards expected to vest. The fair value of stock-settled stock appreciation rights and performance-based awards with market conditions is determined using the Black-Scholes and Monte Carlo simulation models, respectively. The fair value of restricted stock units and performance-based awards with performance conditions is determined by the grant-date closing price of WESCO’s common stock. The forfeiture assumption is based on WESCO’s historical employee behavior that is reviewed on an annual basis. No dividends are assumed. During the three months ended March 31, 2016 and 2015 , WESCO granted the following stock-settled stock appreciation rights, restricted stock units and performance-based awards at the following weighted-average fair values: Three Months Ended March 31, March 31, Stock-settled stock appreciation rights granted 703,510 394,182 Weighted-average fair value $ 12.88 $ 21.68 Restricted stock units granted 143,168 78,292 Weighted-average fair value $ 42.44 $ 69.54 Performance-based awards granted 91,768 59,661 Weighted-average fair value $ 47.00 $ 67.81 The fair value of stock-settled stock appreciation rights was estimated using the following weighted-average assumptions: Three Months Ended March 31, March 31, Risk free interest rate 1.2 % 1.6 % Expected life (in years) 5 5 Expected volatility 32 % 32 % The risk-free interest rate is based on the U.S. Treasury Daily Yield Curve rates as of the grant date. The expected life is based on historical exercise experience and the expected volatility is based on the volatility of the Company's daily stock prices over a five-year period preceding the grant date. The following table sets forth a summary of stock-settled stock appreciation rights and related information for the three months ended March 31, 2016 : Awards Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (In years) Aggregate Intrinsic Value (In thousands) Outstanding at December 31, 2015 2,567,021 $ 54.47 Granted 703,510 42.50 Exercised — — Forfeited (5,490 ) 67.15 Outstanding at March 31, 2016 3,265,041 51.86 5.5 $ 31,627 Exercisable at March 31, 2016 2,269,315 $ 52.01 3.7 $ 23,021 The following table sets forth a summary of time-based restricted stock units and related information for the three months ended March 31, 2016 : Awards Weighted- Average Fair Value Unvested at December 31, 2015 175,411 $ 74.52 Granted 143,168 42.44 Vested (50,830 ) 73.08 Forfeited (460 ) 78.05 Unvested at March 31, 2016 267,289 $ 57.78 Performance shares are awards for which the vesting will occur based on market or performance conditions. The following table sets forth a summary of performance-based awards for the three months ended March 31, 2016 : Awards Weighted- Average Fair Value Unvested at December 31, 2015 114,520 $ 76.48 Granted 91,768 47.00 Vested — — Forfeited (33,774 ) 78.37 Unvested at March 31, 2016 172,514 $ 60.43 The fair value of the performance shares granted during the three months ended March 31, 2016 was estimated using the following weighted-average assumptions: Weighted-Average Assumptions Grant date share price $ 42.44 WESCO expected volatility 26.3 % Peer group median volatility 24.2 % Risk-free interest rate 0.89 % Correlation of peer company returns 121.5 % The unvested performance-based awards in the table above include 86,257 shares in which vesting of the ultimate number of shares is dependent upon WESCO's total stockholder return in relation to the total stockholder return of a select group of peer companies over a three-year period. These awards are accounted for as awards with market conditions; compensation cost is recognized over the service period, regardless of whether the market conditions are achieved and the awards ultimately vest. Vesting of the remaining 86,257 shares of performance-based awards in the table above is dependent upon the three-year average growth rate of WESCO's net income. These awards are accounted for as awards with performance conditions; compensation cost is recognized over the performance period based upon WESCO's determination of whether it is probable that the performance targets will be achieved. WESCO recognized $3.6 million and $3.8 million of non-cash stock-based compensation expense, which is included in selling, general and administrative expenses, for the three months ended March 31, 2016 and 2015 , respectively. As of March 31, 2016 , there was $30.5 million of total unrecognized compensation cost related to non-vested stock-based compensation arrangements for all awards previously made, of which approximately $11.4 million is expected to be recognized over the remainder of 2016 , $11.5 million in 2017 , $6.8 million in 2018 and $0.8 million in 2019 . During the three months ended March 31, 2016 and 2015 , the total intrinsic value of all awards exercised was $2.2 million and $7.7 million , respectively. The gross deferred tax benefit associated with the exercise of awards for the three months ended March 31, 2016 and 2015 totaled $0.8 million and $2.6 million , respectively, and was recorded as an increase to additional capital.

EARNINGS PER SHARE

EARNINGS PER SHARE	3 Months Ended
	Mar. 31, 2016
Earnings Per Share [Abstract]
EARNINGS PER SHARE	EARNINGS PER SHARE Basic earnings per share is computed by dividing net income by the weighted-average number of common shares outstanding during the periods. Diluted earnings per share is computed by dividing net income by the weighted-average common shares and common share equivalents outstanding during the periods. The dilutive effect of common share equivalents is considered in the diluted earnings per share computation using the treasury stock method, which includes consideration of dilutive equity awards and contingently convertible debt. The following table sets forth the details of basic and diluted earnings per share: Three Months Ended March 31, (In thousands, except per share data) 2016 2015 Net income attributable to WESCO International, Inc. $ 36,053 $ 47,031 Weighted-average common shares outstanding used in computing basic earnings per share 42,210 44,406 Common shares issuable upon exercise of dilutive equity awards 414 824 Common shares issuable from contingently convertible debentures (see below for basis of calculation) 4,189 6,966 Weighted-average common shares outstanding and common share equivalents used in computing diluted earnings per share 46,813 52,196 Earnings per share attributable to WESCO International, Inc. Basic $ 0.85 $ 1.06 Diluted $ 0.77 $ 0.90 For the three months ended March 31, 2016 and 2015 , the computation of diluted earnings per share attributable to WESCO International, Inc. excluded stock-based awards of approximately 2.3 million and 0.9 million , respectively. These amounts were excluded because their effect would have been antidilutive. Because of WESCO’s obligation to settle the par value of the 2029 Debentures in cash upon conversion, WESCO is required to include shares underlying the 2029 Debentures in its diluted weighted-average shares outstanding when the average stock price per share for the period exceeds the conversion price of the debentures. Only the number of shares that would be issuable under the treasury stock method of accounting for share dilution are included, which is based upon the amount by which the average stock price exceeds the conversion price. The conversion price of the 2029 Debentures is $28.87 . Share dilution as of March 31, 2016 is limited to a maximum of 11,947,533 shares for the 2029 Debentures. For the three months ended March 31, 2016 and 2015 , the effect of the 2029 Debentures on diluted earnings per share attributable to WESCO International, Inc. was a decrease of $0.08 and $0.14 , respectively. In December 2014, the Company's Board of Directors authorized the repurchase of up to $300 million of the Company's common stock through December 31, 2017. During the year ended December 31, 2015 , the Company entered into accelerated stock repurchase agreements (the "ASR Transactions") with certain financial institutions to purchase shares of its common stock. In exchange for up-front cash payments totaling $150 million , the Company received 2,468,576 shares, of which 300,651 shares were received during the three months ended March 31, 2015 . The total number of shares ultimately delivered under the ASR Transactions was determined by the average of the volume-weighted-average prices of the Company's common stock for each exchange business day during the respective settlement valuation periods. WESCO funded the repurchases with borrowings under its prior revolving credit facility. For purposes of computing earnings per share, share repurchases were reflected as a reduction to common shares outstanding on the respective share delivery dates.

EMPLOYEE BENEFIT PLANS

EMPLOYEE BENEFIT PLANS	3 Months Ended
	Mar. 31, 2016
Compensation and Retirement Disclosure [Abstract]
EMPLOYEE BENEFIT PLANS	EMPLOYEE BENEFIT PLANS A majority of WESCO’s employees are covered by defined contribution retirement savings plans for their services rendered subsequent to WESCO’s formation. WESCO also offers a deferred compensation plan for select individuals. For U.S. participants, WESCO will make contributions in an amount equal to 50% of the participant’s total monthly contributions up to a maximum of 6% of eligible compensation. For Canadian participants, WESCO will make contributions in an amount ranging from 3% to 5% of the participant’s eligible compensation based on years of continuous service. In addition, for U.S. participants, employer contributions may be made at the discretion of the Board of Directors. For the three months ended March 31, 2016 and 2015 , WESCO incurred charges of $8.3 million and $5.1 million , respectively, for all such plans. Contributions are made in cash to defined contribution retirement savings plans. The deferred compensation plan is an unfunded plan. Employees have the option to transfer balances allocated to their accounts in the defined contribution retirement savings plan and the deferred compensation plan into any of the available investment options. In connection with the December 14, 2012 acquisition of EECOL, the Company assumed a contributory defined benefit plan covering substantially all Canadian employees of EECOL and a Supplemental Executive Retirement Plan for certain executives of EECOL. The following table reflects the components of net periodic benefit costs for the Company's defined benefit plans: Three Months Ended March 31, (In thousands of dollars) 2016 2015 Service cost $ 923 $ 1,171 Interest cost 926 1,042 Expected return on plan assets (1,279 ) (1,366 ) Recognized actuarial gain (10 ) (4 ) Net periodic benefit cost $ 560 $ 843 During the three months ended March 31, 2016 and 2015 , the Company made aggregate cash contributions of $0.5 million to its defined benefit plans.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	3 Months Ended
	Mar. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES WESCO is subject to the laws and regulations of states and other jurisdictions concerning the identification, reporting and escheatment (the transfer of property to the state) of unclaimed or abandoned funds, and is subject to audit and examination for compliance with these requirements. WESCO Distribution, Inc. is currently undergoing a compliance audit in the State of Delaware concerning the identification, reporting and escheatment of unclaimed or abandoned property. A third party auditor is conducting the audit on behalf of the State, and the Company has been working with an outside consultant during the audit process and in discussions with the auditors. The Company is defending the audit, the outcome of which cannot be predicted with certainty at this time. After the third party auditor completes its field work, it is expected to issue preliminary findings for review by the Company and the State, and thereafter the auditor is expected to issue a final report of examination. If the Company and State do not reach resolution after further discussion, the State issues a demand for payment, which the Company may either agree to pay or appeal, in full or in part. The Company has recorded a liability for unclaimed property based on the facts currently known to the Company. In October 2014, WESCO was notified that the New York County District Attorney’s Office is conducting a criminal investigation involving minority and disadvantaged business contracting practices in the construction industry in New York City and that various contractors, minority and disadvantaged business firms, and their material suppliers, including the Company, are a part of this investigation. The Company has commenced an internal review of this matter and intends to cooperate with the government investigation. The Company cannot predict the outcome or impact of the matter at this time, but could be subject to fines, penalties or other adverse consequences. Based on the facts currently known to the Company, it cannot reasonably estimate a range of exposure to potential liability at this time.

INCOME TAXES

INCOME TAXES	3 Months Ended
	Mar. 31, 2016
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The effective tax rate for the three months ended March 31, 2016 and 2015 was 31.9% and 29.4% , respectively. WESCO’s effective tax rate is lower than the federal statutory rate of 35% due to benefits resulting from the tax effect of intercompany financing and lower rates on foreign earnings, which are partially offset by nondeductible expenses and state taxes. During the three months ended March 31, 2016 , WESCO recognized a discrete item related to the settlement of an outstanding tax matter which increased the effective tax rate by 3.4 percentage points. There were no significant discrete items in the comparable prior year quarter. The total amount of unrecognized tax benefits was reduced by $2.3 million during the three months ended March 31, 2016 to $3.1 million due to the settlement of outstanding tax matters and the expiration of statutes of limitation. At March 31, 2016 , the amount of unrecognized tax benefits that would affect the effective tax rate if recognized in the consolidated financial statements was $4.5 million . It is reasonably possible that the amount of unrecognized tax benefits will decrease by approximately $1.0 million within the next twelve months due to the expiration of statutes of limitation and the settlement of state audits. Of this amount, $0.3 million could impact the effective tax rate.

OTHER FINANCIAL INFORMATION

OTHER FINANCIAL INFORMATION	3 Months Ended
	Mar. 31, 2016
Condensed Financial Information [Abstract]
OTHER FINANCIAL INFORMATION	WESCO International, Inc. has outstanding $344.9 million in aggregate principal amount of 2029 Debentures. The 2029 Debentures are fully and unconditionally guaranteed by WESCO Distribution, Inc., a 100% owned subsidiary of WESCO International, Inc., on a senior subordinated basis to all existing and future senior indebtedness of WESCO Distribution, Inc. WESCO Distribution, Inc. has outstanding $500 million in aggregate principal amount of 5.375% Senior Notes due 2021 (the "2021 Notes"). The 2021 Notes are unsecured senior obligations of WESCO Distribution, Inc. and are fully and unconditionally guaranteed on a senior unsecured basis by WESCO International, Inc. Condensed consolidating financial information for WESCO International, Inc., WESCO Distribution, Inc. and the non-guarantor subsidiaries is presented in the following tables. Condensed Consolidating Balance Sheet March 31, 2016 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Cash and cash equivalents $ — $ 36,166 $ 111,668 $ — $ 147,834 Trade accounts receivable, net — — 1,091,504 — 1,091,504 Inventories — 393,120 450,986 — 844,106 Prepaid expenses and other current assets 8 34,281 165,680 (8,971 ) 190,998 Total current assets 8 463,567 1,819,838 (8,971 ) 2,274,442 Intercompany receivables, net — — 1,931,545 (1,931,545 ) — Property, buildings and equipment, net — 54,688 112,851 — 167,539 Intangible assets, net — 3,909 417,807 — 421,716 Goodwill — 255,251 1,507,442 — 1,762,693 Investments in affiliates 3,429,718 3,900,638 — (7,330,356 ) — Other assets — 23,745 40,693 — 64,438 Total assets $ 3,429,726 $ 4,701,798 $ 5,830,176 $ (9,270,872 ) $ 4,690,828 Accounts payable $ — $ 404,468 $ 330,443 $ — $ 734,911 Short-term debt — — 48,251 — 48,251 Other current liabilities 10,082 62,450 136,579 (8,971 ) 200,140 Total current liabilities 10,082 466,918 515,273 (8,971 ) 983,302 Intercompany payables, net 1,323,843 607,702 — (1,931,545 ) — Long-term debt, net 178,896 717,869 494,462 — 1,391,227 Other noncurrent liabilities 19,101 226,601 177,115 — 422,817 Total WESCO International, Inc. stockholders' equity 1,897,804 2,682,708 4,647,648 (7,330,356 ) 1,897,804 Noncontrolling interests — — (4,322 ) — (4,322 ) Total liabilities and stockholders’ equity $ 3,429,726 $ 4,701,798 $ 5,830,176 $ (9,270,872 ) $ 4,690,828 Condensed Consolidating Balance Sheet December 31, 2015 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Cash and cash equivalents $ — $ 38,963 $ 121,316 $ — $ 160,279 Trade accounts receivable, net — — 1,075,257 — 1,075,257 Inventories — 376,641 433,426 — 810,067 Prepaid expenses and other current assets 15 47,290 173,596 (8,970 ) 211,931 Total current assets 15 462,894 1,803,595 (8,970 ) 2,257,534 Intercompany receivables, net — — 1,964,848 (1,964,848 ) — Property, buildings and equipment, net — 56,921 109,818 — 166,739 Intangible assets, net — 4,072 399,577 — 403,649 Goodwill — 255,251 1,426,411 — 1,681,662 Investments in affiliates 3,309,006 3,827,069 — (7,136,075 ) — Other assets — 32,601 27,541 — 60,142 Total assets $ 3,309,021 $ 4,638,808 $ 5,731,790 $ (9,109,893 ) $ 4,569,726 Accounts payable $ — $ 414,524 $ 300,995 $ — $ 715,519 Short-term debt — — 43,314 — 43,314 Other current liabilities 15,254 55,129 127,555 (8,970 ) 188,968 Total current liabilities 15,254 469,653 471,864 (8,970 ) 947,801 Intercompany payables, net 1,320,240 644,608 — (1,964,848 ) — Long-term debt, net 177,753 737,490 523,819 — 1,439,062 Other noncurrent liabilities 19,102 216,515 173,375 — 408,992 Total WESCO International, Inc. stockholders' equity 1,776,672 2,570,542 4,565,533 (7,136,075 ) 1,776,672 Noncontrolling interests — — (2,801 ) — (2,801 ) Total liabilities and stockholders’ equity $ 3,309,021 $ 4,638,808 $ 5,731,790 $ (9,109,893 ) $ 4,569,726 Condensed Consolidating Statement of Income (Loss) and Comprehensive Income Three Months Ended March 31, 2016 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 800,490 $ 1,000,045 $ (24,574 ) $ 1,775,961 Cost of goods sold (excluding depreciation and amortization) — 639,673 805,694 (24,574 ) 1,420,793 Selling, general and administrative expenses (378 ) 80,208 189,456 — 269,286 Depreciation and amortization — 5,106 11,268 — 16,374 Results of affiliates’ operations 38,459 (8,684 ) — (29,775 ) — Interest expense (income), net 6,318 18,859 (6,348 ) — 18,829 Provision for income taxes (2,015 ) 18,046 114 — 16,145 Net income (loss) 34,534 29,914 (139 ) (29,775 ) 34,534 Net loss attributable to noncontrolling interests — — (1,519 ) — (1,519 ) Net income attributable to WESCO International, Inc. $ 34,534 $ 29,914 $ 1,380 $ (29,775 ) $ 36,053 Other comprehensive income (loss): Foreign currency translation adjustments 82,270 82,270 82,270 (164,540 ) 82,270 Post retirement benefit plan adjustments $ (16 ) $ (16 ) $ (16 ) $ 32 $ (16 ) Comprehensive income attributable to WESCO International, Inc. $ 116,788 $ 112,168 $ 83,634 $ (194,283 ) $ 118,307 Condensed Consolidating Statement of Income and Comprehensive Loss Three Months Ended March 31, 2015 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 839,282 $ 1,005,250 $ (28,202 ) $ 1,816,330 Cost of goods sold (excluding depreciation and amortization) — 669,806 807,035 (28,202 ) 1,448,639 Selling, general and administrative expenses 8 136,411 128,166 — 264,585 Depreciation and amortization — 4,834 11,087 — 15,921 Results of affiliates’ operations 51,165 36,268 — (87,433 ) — Interest expense (income), net 6,187 18,640 (3,933 ) — 20,894 Provision for income taxes (1,822 ) 2,821 18,499 — 19,498 Net income 46,792 43,038 44,396 (87,433 ) 46,793 Net loss attributable to noncontrolling interests — — (238 ) — (238 ) Net income attributable to WESCO International, Inc. $ 46,792 $ 43,038 $ 44,634 $ (87,433 ) $ 47,031 Other comprehensive loss: Foreign currency translation adjustments (113,814 ) (113,814 ) (113,814 ) 227,628 (113,814 ) Comprehensive loss attributable to WESCO International, Inc. $ (67,022 ) $ (70,776 ) $ (69,180 ) $ 140,195 $ (66,783 ) Condensed Consolidating Statement of Cash Flows Three Months Ended March 31, 2016 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net cash (used in) provided by operating activities $ (3,138 ) $ 62,678 $ 19,028 $ — $ 78,568 Investing activities: Capital expenditures — (3,084 ) (524 ) — (3,608 ) Acquisition payments, net of cash acquired — (50,348 ) — — (50,348 ) Dividends received from subsidiaries — 15,310 — (15,310 ) — Other — (14,548 ) (3,783 ) 10,183 (8,148 ) Net cash used in investing activities — (52,670 ) (4,307 ) (5,127 ) (62,104 ) Financing activities: Borrowings 3,603 284,972 69,969 (14,548 ) 343,996 Repayments — (309,337 ) (84,893 ) 4,365 (389,865 ) Increase in bank overdrafts — 11,972 — — 11,972 Dividends paid by subsidiaries — — (15,310 ) 15,310 — Other (465 ) (412 ) — — (877 ) Net cash provided by (used in) financing activities 3,138 (12,805 ) (30,234 ) 5,127 (34,774 ) Effect of exchange rate changes on cash and cash equivalents — — 5,865 — 5,865 Net change in cash and cash equivalents — (2,797 ) (9,648 ) — (12,445 ) Cash and cash equivalents at the beginning of period — 38,963 121,316 — 160,279 Cash and cash equivalents at the end of period $ — $ 36,166 $ 111,668 $ — $ 147,834 Condensed Consolidating Statement of Cash Flows Three Months Ended March 31, 2015 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net cash (used in) provided by operating activities $ (4,441 ) $ 53,333 $ 41,164 $ — $ 90,056 Investing activities: Capital expenditures — (4,005 ) (1,021 ) — (5,026 ) Dividends received from subsidiaries — 16,090 — (16,090 ) — Other — (43,850 ) 5,150 39,485 785 Net cash used in investing activities — (31,765 ) 4,129 23,395 (4,241 ) Financing activities: Borrowings 32,125 218,699 162,325 (43,850 ) 369,299 Repayments — (226,064 ) (166,580 ) 4,365 (388,279 ) Equity activities (27,602 ) — — — (27,602 ) Decrease in bank overdrafts — (6,725 ) — — (6,725 ) Dividends paid by subsidiaries — — (16,090 ) 16,090 — Other (82 ) (402 ) — — (484 ) Net cash provided by (used in) financing activities 4,441 (14,492 ) (20,345 ) (23,395 ) (53,791 ) Effect of exchange rate changes on cash and cash equivalents — — (5,992 ) — (5,992 ) Net change in cash and cash equivalents — 7,076 18,956 — 26,032 Cash and cash equivalents at the beginning of period — 32,508 95,811 — 128,319 Cash and cash equivalents at the end of period $ — $ 39,584 $ 114,767 $ — $ 154,351 Revisions The unaudited Condensed Consolidating Statement of Cash Flows for the three months ended March 31, 2015 was revised to appropriately present dividends paid by the non-guarantor subsidiaries and dividends received by WESCO Distribution, Inc. The revisions did not impact the consolidated amounts previously reported, nor did they impact the Company's obligations under the 2021 Notes or the 2029 Debentures. As described in Note 1, the Company adopted certain accounting pronouncements during the first quarter of 2016 that were effective beginning this fiscal year. The adoption of such guidance resulted in certain reclassifications to amounts previously reported in the Condensed Consolidating Balance Sheet at December 31, 2015 .

Subsequent Events SUBSEQUENT EV

Subsequent Events SUBSEQUENT EVENTS (Notes)	3 Months Ended
	Mar. 31, 2016
Subsequent Events [Abstract]
Subsequent Events [Text Block]	11. SUBSEQUENT EVENTS The Company evaluated subsequent events and concluded that no subsequent events have occurred that would require recognition in the unaudited Condensed Consolidated Financial Statements or disclosure in the Notes thereto except as described below. On May 3, 2016, the Company issued a press release announcing the resignation of its Chief Financial Officer with such resignation to be effective on May 31, 2016. The Company has appointed an interim Chief Financial Officer and has commenced a search process for a new Chief Financial Officer.

GOODWILL (Notes)

GOODWILL (Notes)	3 Months Ended
	Mar. 31, 2016
Goodwill [Line Items]
Goodwill Disclosure [Text Block]	4. GOODWILL The following table sets forth the changes in the carrying value of goodwill: Three Months Ended March 31, March 31, (In thousands) Beginning balance January 1 $ 1,681,662 $ 1,735,440 Foreign currency exchange rate changes 39,918 (59,859 ) Additions to goodwill for acquisitions 41,113 — Ending balance March 31 $ 1,762,693 $ 1,675,581

ACCOUNTING POLICIES (Policies)

ACCOUNTING POLICIES (Policies)	3 Months Ended
	Mar. 31, 2016
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying 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 information should be read in conjunction with the audited Consolidated Financial Statements and Notes thereto included in WESCO’s 2015 Annual Report on Form 10-K as filed with the SEC on February 22, 2016. The Condensed Consolidated Balance Sheet at December 31, 2015 was derived from the audited Consolidated Financial Statements as of that date, but does not include all of the disclosures required by accounting principles generally accepted in the United States of America. The unaudited Condensed Consolidated Balance Sheet as of March 31, 2016 , the unaudited Condensed Consolidated Statements of Income and Comprehensive Income (Loss) for the three months ended March 31, 2016 and 2015 , respectively, and the unaudited Condensed Consolidated Statements of Cash Flows for the three months ended March 31, 2016 and 2015 , 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 presented herein. All adjustments reflected in the unaudited condensed consolidated financial information are of a normal recurring nature unless indicated. The results for the interim periods presented herein are not necessarily indicative of the results to be expected for the full year.
Reclassification	.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company measures the fair value of financial assets and liabilities in accordance with Financial Accounting Standards Board (FASB) Accounting Standards Codification (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 that prioritizes the inputs to valuation techniques used to measure fair value and requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to measurements involving significant unobservable inputs (Level 3 measurements). The three levels of the fair value hierarchy are as follows: • Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities that are accessible at the measurement date. • 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 March 31, 2016 , the carrying value of WESCO’s 6.0% Convertible Senior Debentures due 2029 (the "2029 Debentures") was $178.9 million and the fair value was approximately $663.9 million . At December 31, 2015 , the carrying value of WESCO’s 2029 Debentures was $177.8 million and the fair value was approximately $514.2 million . The reported carrying amounts of WESCO’s other debt instruments approximate their fair values. The Company uses a market approach to fair value all of its debt instruments, utilizing quoted prices in active markets, interest rates and other relevant information generated by market transactions involving similar instruments. Therefore, all of the Company's debt instruments are classified as Level 2 within the valuation hierarchy. For all of the Company's remaining financial instruments, consisting of cash and cash equivalents, accounts receivable, accounts payable and other accrued liabilities, carrying values are considered to approximate fair value due to the short maturity of these instruments.
New Accounting Pronouncements, Policy [Policy Text Block]	Recently Adopted Accounting Pronouncements In April 2015, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2015-03, Simplifying the Presentation of Debt Issuance Costs , which simplifies the presentation of debt issuance costs by requiring that debt issuance costs related to a recognized liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. The Company adopted this new guidance on a retrospective basis effective January 1, 2016. Accordingly, the Company reclassified approximately $17.7 million of debt issuance costs from other noncurrent assets to long-term debt in the balance sheet as of December 31, 2015 . In May 2015, the FASB issued ASU 2015-07, Disclosures for Investments in Certain Entities That Calculate Net Asset Value per Share (or Its Equivalent). This updated guidance removes the requirement to categorize investments for which fair value is measured using the net asset value (NAV) per share practical expedient within the fair value hierarchy. The amendments in this ASU are effective beginning in the first quarter of 2016 and will be applied retrospectively. This updated guidance will impact the Company's defined benefit plan disclosure in its Annual Report on Form 10-K for the fiscal year ending December 31, 2016 . Specifically, investments for which fair value is measured using the NAV per share practical expedient will be removed from the fair value hierarchy in all periods presented. In November 2015, the FASB issued ASU 2015-17, Balance Sheet Classification of Deferred Taxes . This ASU simplifies the presentation of deferred income taxes by requiring that all deferred tax assets and liabilities, along with any related valuation allowance, be classified as noncurrent in the balance sheet. The Company elected to early adopt this ASU on a prospective basis during the first quarter of 2016 . The adoption of this ASU did not have a material impact on WESCO's financial position and it had no impact on its results of operations or cash flows. Recently Issued Accounting Pronouncements In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers: Deferral of Effective Date . The Company previously reported that in May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers, which provides a framework for addressing revenue recognition issues and replaces almost all existing revenue recognition guidance in current U.S. generally accepted accounting principles. The core principle of ASU 2014-09 is for companies to recognize revenue for the transfer of goods or services to customers in amounts that reflect the consideration to which the company expects to be entitled in exchange for those goods or services. ASU 2014-09 will also result in enhanced disclosures about revenue, provide guidance for transactions that were not previously addressed comprehensively, and improve guidance for multiple-element arrangements. The amendments in ASU 2015-14 defer the effective date of the new revenue recognition guidance to annual reporting periods beginning after December 15, 2017, including interim periods within that reporting period. Early adoption is permitted to the original effective date of December 15, 2016, including interim periods within that reporting period. Management is currently evaluating the future impact of this guidance on WESCO's consolidated financial statements and notes thereto. In February 2016, the FASB issued ASU 2016-02, Leases , a comprehensive new standard that amends various aspects of existing accounting guidance for leases, including the recognition of a right-of-use asset and a lease liability on the balance sheet and disclosing key information about leasing arrangements. This guidance is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Early adoption is permitted. The new leasing standard requires modified retrospective transition, which requires application of the new guidance at the beginning of the earliest comparative period presented in the year of adoption. Management is currently evaluating the impact of this new standard on WESCO's consolidated financial statements and notes thereto. In March 2016 and April 2016, the FASB issued ASU 2016-08, Principal versus Agent Considerations (Reporting Revenue Gross versus Net) , and ASU 2016-10, Identifying Performance Obligations and Licensing , respectively. The amendments in these ASUs clarify the implementation guidance on principal versus agent considerations and identifying performance obligations, respectively. Neither ASU changed the core principle in the revenue recognition standard outlined above. These ASUs apply to all entities that enter into contracts with customers to transfer goods or services (that are an output of the entity’s ordinary activities) in exchange for consideration. The effective dates and transition requirements for these ASUs are the same as the effective dates and transition requirements of the revenue recognition guidance outlined above. Management is currently evaluating the impact of these ASUs on WESCO's consolidated financial statements and notes thereto. In March 2016, the FASB issued ASU 2016-09, Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting , which simplifies several aspects of accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. The amendments in this ASU affect all entities that issue share-based payment awards to their employees. Management is currently evaluating the impact of this accounting standard on WESCO's consolidated financial statements and notes thereto. Other pronouncements issued by the FASB or other authoritative accounting standards groups with future effective dates are either not applicable or are not expected to be significant to WESCO’s financial position, results of operations or cash flows.

ACQUISITIONS (Tables)

ACQUISITIONS (Tables)	3 Months Ended
	Mar. 31, 2016
Business Combinations [Abstract]
Schedule of Business Acquisitions, by Acquisition [Table Text Block]	Three Months Ended (In thousands of dollars) March 31, Fair value of assets acquired $ 77,005 Fair value of liabilities assumed 25,005 Cash paid for acquisitions $ 52,000 Supplemental cash flow disclosure: Cash paid for acquisitions $ 52,000 Less: cash acquired (1,652 ) Cash paid for acquisitions, net of cash acquired $ 50,348

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	3 Months Ended
	Mar. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]	During the three months ended March 31, 2016 and 2015 , WESCO granted the following stock-settled stock appreciation rights, restricted stock units and performance-based awards at the following weighted-average fair values: Three Months Ended March 31, March 31, Stock-settled stock appreciation rights granted 703,510 394,182 Weighted-average fair value $ 12.88 $ 21.68 Restricted stock units granted 143,168 78,292 Weighted-average fair value $ 42.44 $ 69.54 Performance-based awards granted 91,768 59,661 Weighted-average fair value $ 47.00 $ 67.81
Schedule of Share-based Compensation, Stock Options and Stock Appreciation Rights Award Activity [Table Text Block]	The following table sets forth a summary of stock-settled stock appreciation rights and related information for the three months ended March 31, 2016 : Awards Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (In years) Aggregate Intrinsic Value (In thousands) Outstanding at December 31, 2015 2,567,021 $ 54.47 Granted 703,510 42.50 Exercised — — Forfeited (5,490 ) 67.15 Outstanding at March 31, 2016 3,265,041 51.86 5.5 $ 31,627 Exercisable at March 31, 2016 2,269,315 $ 52.01 3.7 $ 23,021
Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block]	The following table sets forth a summary of time-based restricted stock units and related information for the three months ended March 31, 2016 : Awards Weighted- Average Fair Value Unvested at December 31, 2015 175,411 $ 74.52 Granted 143,168 42.44 Vested (50,830 ) 73.08 Forfeited (460 ) 78.05 Unvested at March 31, 2016 267,289 $ 57.78
Schedule of Nonvested Performance-based Units Activity [Table Text Block]	The following table sets forth a summary of performance-based awards for the three months ended March 31, 2016 : Awards Weighted- Average Fair Value Unvested at December 31, 2015 114,520 $ 76.48 Granted 91,768 47.00 Vested — — Forfeited (33,774 ) 78.37 Unvested at March 31, 2016 172,514 $ 60.43
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]	Weighted-Average Assumptions Grant date share price $ 42.44 WESCO expected volatility 26.3 % Peer group median volatility 24.2 % Risk-free interest rate 0.89 % Correlation of peer company returns 121.5 %
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]	Three Months Ended March 31, March 31, Risk free interest rate 1.2 % 1.6 % Expected life (in years) 5 5 Expected volatility 32 % 32 %

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	3 Months Ended
	Mar. 31, 2016
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]	The following table sets forth the details of basic and diluted earnings per share: Three Months Ended March 31, (In thousands, except per share data) 2016 2015 Net income attributable to WESCO International, Inc. $ 36,053 $ 47,031 Weighted-average common shares outstanding used in computing basic earnings per share 42,210 44,406 Common shares issuable upon exercise of dilutive equity awards 414 824 Common shares issuable from contingently convertible debentures (see below for basis of calculation) 4,189 6,966 Weighted-average common shares outstanding and common share equivalents used in computing diluted earnings per share 46,813 52,196 Earnings per share attributable to WESCO International, Inc. Basic $ 0.85 $ 1.06 Diluted $ 0.77 $ 0.90

EMPLOYEE BENEFIT PLANS Schedule

EMPLOYEE BENEFIT PLANS Schedule of Net Benefit Costs (Tables)	3 Months Ended
	Mar. 31, 2016
Postemployment Benefits [Abstract]
Schedule of Net Benefit Costs [Table Text Block]	The following table reflects the components of net periodic benefit costs for the Company's defined benefit plans: Three Months Ended March 31, (In thousands of dollars) 2016 2015 Service cost $ 923 $ 1,171 Interest cost 926 1,042 Expected return on plan assets (1,279 ) (1,366 ) Recognized actuarial gain (10 ) (4 ) Net periodic benefit cost $ 560 $ 843

OTHER FINANCIAL INFORMATION (Ta

OTHER FINANCIAL INFORMATION (Tables)	3 Months Ended
	Mar. 31, 2016
Condensed Balance Sheet Statements, Captions [Line Items]
Condensed Balance Sheet [Table Text Block]	Condensed Consolidating Balance Sheet March 31, 2016 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Cash and cash equivalents $ — $ 36,166 $ 111,668 $ — $ 147,834 Trade accounts receivable, net — — 1,091,504 — 1,091,504 Inventories — 393,120 450,986 — 844,106 Prepaid expenses and other current assets 8 34,281 165,680 (8,971 ) 190,998 Total current assets 8 463,567 1,819,838 (8,971 ) 2,274,442 Intercompany receivables, net — — 1,931,545 (1,931,545 ) — Property, buildings and equipment, net — 54,688 112,851 — 167,539 Intangible assets, net — 3,909 417,807 — 421,716 Goodwill — 255,251 1,507,442 — 1,762,693 Investments in affiliates 3,429,718 3,900,638 — (7,330,356 ) — Other assets — 23,745 40,693 — 64,438 Total assets $ 3,429,726 $ 4,701,798 $ 5,830,176 $ (9,270,872 ) $ 4,690,828 Accounts payable $ — $ 404,468 $ 330,443 $ — $ 734,911 Short-term debt — — 48,251 — 48,251 Other current liabilities 10,082 62,450 136,579 (8,971 ) 200,140 Total current liabilities 10,082 466,918 515,273 (8,971 ) 983,302 Intercompany payables, net 1,323,843 607,702 — (1,931,545 ) — Long-term debt, net 178,896 717,869 494,462 — 1,391,227 Other noncurrent liabilities 19,101 226,601 177,115 — 422,817 Total WESCO International, Inc. stockholders' equity 1,897,804 2,682,708 4,647,648 (7,330,356 ) 1,897,804 Noncontrolling interests — — (4,322 ) — (4,322 ) Total liabilities and stockholders’ equity $ 3,429,726 $ 4,701,798 $ 5,830,176 $ (9,270,872 ) $ 4,690,828 Condensed Consolidating Balance Sheet December 31, 2015 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Cash and cash equivalents $ — $ 38,963 $ 121,316 $ — $ 160,279 Trade accounts receivable, net — — 1,075,257 — 1,075,257 Inventories — 376,641 433,426 — 810,067 Prepaid expenses and other current assets 15 47,290 173,596 (8,970 ) 211,931 Total current assets 15 462,894 1,803,595 (8,970 ) 2,257,534 Intercompany receivables, net — — 1,964,848 (1,964,848 ) — Property, buildings and equipment, net — 56,921 109,818 — 166,739 Intangible assets, net — 4,072 399,577 — 403,649 Goodwill — 255,251 1,426,411 — 1,681,662 Investments in affiliates 3,309,006 3,827,069 — (7,136,075 ) — Other assets — 32,601 27,541 — 60,142 Total assets $ 3,309,021 $ 4,638,808 $ 5,731,790 $ (9,109,893 ) $ 4,569,726 Accounts payable $ — $ 414,524 $ 300,995 $ — $ 715,519 Short-term debt — — 43,314 — 43,314 Other current liabilities 15,254 55,129 127,555 (8,970 ) 188,968 Total current liabilities 15,254 469,653 471,864 (8,970 ) 947,801 Intercompany payables, net 1,320,240 644,608 — (1,964,848 ) — Long-term debt, net 177,753 737,490 523,819 — 1,439,062 Other noncurrent liabilities 19,102 216,515 173,375 — 408,992 Total WESCO International, Inc. stockholders' equity 1,776,672 2,570,542 4,565,533 (7,136,075 ) 1,776,672 Noncontrolling interests — — (2,801 ) — (2,801 ) Total liabilities and stockholders’ equity $ 3,309,021 $ 4,638,808 $ 5,731,790 $ (9,109,893 ) $ 4,569,726

OTHER FINANCIAL INFORMATION Con

OTHER FINANCIAL INFORMATION Condensed Income Statement (Tables)	3 Months Ended
	Mar. 31, 2016
Condensed Income Statements, Captions [Line Items]
Condensed Income Statement [Table Text Block]	Condensed Consolidating Statement of Income (Loss) and Comprehensive Income Three Months Ended March 31, 2016 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 800,490 $ 1,000,045 $ (24,574 ) $ 1,775,961 Cost of goods sold (excluding depreciation and amortization) — 639,673 805,694 (24,574 ) 1,420,793 Selling, general and administrative expenses (378 ) 80,208 189,456 — 269,286 Depreciation and amortization — 5,106 11,268 — 16,374 Results of affiliates’ operations 38,459 (8,684 ) — (29,775 ) — Interest expense (income), net 6,318 18,859 (6,348 ) — 18,829 Provision for income taxes (2,015 ) 18,046 114 — 16,145 Net income (loss) 34,534 29,914 (139 ) (29,775 ) 34,534 Net loss attributable to noncontrolling interests — — (1,519 ) — (1,519 ) Net income attributable to WESCO International, Inc. $ 34,534 $ 29,914 $ 1,380 $ (29,775 ) $ 36,053 Other comprehensive income (loss): Foreign currency translation adjustments 82,270 82,270 82,270 (164,540 ) 82,270 Post retirement benefit plan adjustments $ (16 ) $ (16 ) $ (16 ) $ 32 $ (16 ) Comprehensive income attributable to WESCO International, Inc. $ 116,788 $ 112,168 $ 83,634 $ (194,283 ) $ 118,307 Condensed Consolidating Statement of Income and Comprehensive Loss Three Months Ended March 31, 2015 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 839,282 $ 1,005,250 $ (28,202 ) $ 1,816,330 Cost of goods sold (excluding depreciation and amortization) — 669,806 807,035 (28,202 ) 1,448,639 Selling, general and administrative expenses 8 136,411 128,166 — 264,585 Depreciation and amortization — 4,834 11,087 — 15,921 Results of affiliates’ operations 51,165 36,268 — (87,433 ) — Interest expense (income), net 6,187 18,640 (3,933 ) — 20,894 Provision for income taxes (1,822 ) 2,821 18,499 — 19,498 Net income 46,792 43,038 44,396 (87,433 ) 46,793 Net loss attributable to noncontrolling interests — — (238 ) — (238 ) Net income attributable to WESCO International, Inc. $ 46,792 $ 43,038 $ 44,634 $ (87,433 ) $ 47,031 Other comprehensive loss: Foreign currency translation adjustments (113,814 ) (113,814 ) (113,814 ) 227,628 (113,814 ) Comprehensive loss attributable to WESCO International, Inc. $ (67,022 ) $ (70,776 ) $ (69,180 ) $ 140,195 $ (66,783 )

OTHER FINANCIAL INFORMATION C24

OTHER FINANCIAL INFORMATION Condensed Cash Flow Statement (Tables)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Condensed Cash Flow Statements, Captions [Line Items]
Condensed Cash Flow Statement [Table Text Block]	Condensed Consolidating Statement of Cash Flows Three Months Ended March 31, 2016 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net cash (used in) provided by operating activities $ (3,138 ) $ 62,678 $ 19,028 $ — $ 78,568 Investing activities: Capital expenditures — (3,084 ) (524 ) — (3,608 ) Acquisition payments, net of cash acquired — (50,348 ) — — (50,348 ) Dividends received from subsidiaries — 15,310 — (15,310 ) — Other — (14,548 ) (3,783 ) 10,183 (8,148 ) Net cash used in investing activities — (52,670 ) (4,307 ) (5,127 ) (62,104 ) Financing activities: Borrowings 3,603 284,972 69,969 (14,548 ) 343,996 Repayments — (309,337 ) (84,893 ) 4,365 (389,865 ) Increase in bank overdrafts — 11,972 — — 11,972 Dividends paid by subsidiaries — — (15,310 ) 15,310 — Other (465 ) (412 ) — — (877 ) Net cash provided by (used in) financing activities 3,138 (12,805 ) (30,234 ) 5,127 (34,774 ) Effect of exchange rate changes on cash and cash equivalents — — 5,865 — 5,865 Net change in cash and cash equivalents — (2,797 ) (9,648 ) — (12,445 ) Cash and cash equivalents at the beginning of period — 38,963 121,316 — 160,279 Cash and cash equivalents at the end of period $ — $ 36,166 $ 111,668 $ — $ 147,834	Condensed Consolidating Statement of Cash Flows Three Months Ended March 31, 2015 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net cash (used in) provided by operating activities $ (4,441 ) $ 53,333 $ 41,164 $ — $ 90,056 Investing activities: Capital expenditures — (4,005 ) (1,021 ) — (5,026 ) Dividends received from subsidiaries — 16,090 — (16,090 ) — Other — (43,850 ) 5,150 39,485 785 Net cash used in investing activities — (31,765 ) 4,129 23,395 (4,241 ) Financing activities: Borrowings 32,125 218,699 162,325 (43,850 ) 369,299 Repayments — (226,064 ) (166,580 ) 4,365 (388,279 ) Equity activities (27,602 ) — — — (27,602 ) Decrease in bank overdrafts — (6,725 ) — — (6,725 ) Dividends paid by subsidiaries — — (16,090 ) 16,090 — Other (82 ) (402 ) — — (484 ) Net cash provided by (used in) financing activities 4,441 (14,492 ) (20,345 ) (23,395 ) (53,791 ) Effect of exchange rate changes on cash and cash equivalents — — (5,992 ) — (5,992 ) Net change in cash and cash equivalents — 7,076 18,956 — 26,032 Cash and cash equivalents at the beginning of period — 32,508 95,811 — 128,319 Cash and cash equivalents at the end of period $ — $ 39,584 $ 114,767 $ — $ 154,351

GOODWILL (Tables)

GOODWILL (Tables)	3 Months Ended
	Mar. 31, 2016
Goodwill [Line Items]
Schedule of Goodwill [Table Text Block]	Three Months Ended March 31, March 31, (In thousands) Beginning balance January 1 $ 1,681,662 $ 1,735,440 Foreign currency exchange rate changes 39,918 (59,859 ) Additions to goodwill for acquisitions 41,113 — Ending balance March 31 $ 1,762,693 $ 1,675,581

ORGANIZATION (Details)

ORGANIZATION (Details)	Mar. 31, 2016customerscountriesbranches
Restructuring Cost and Reserve [Line Items]
Active customers (in customers) | customers	80,000
Full service branches (in branches) | branches	500
Additional countries (in countries) | countries	14

ACCOUNTING POLICIES (Details)

ACCOUNTING POLICIES (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Fixed Rate Debt, Par Value	$ 178.9	$ 177.8
Convertible Debt, Fair Value Disclosures	$ 663.9	$ 514.2

ACQUISITIONS - ACQUISITIONS (De

ACQUISITIONS - ACQUISITIONS (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2016USD ($)branches	Mar. 31, 2015USD ($)	Dec. 31, 2015USD ($)
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	$ 77,005
Payments to Acquire Businesses, Gross	50,348	$ 0
Goodwill, Acquired During Period	41,113	$ 0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	25,005
Payments to Acquire Businesses, Gross	$ 52,000
Number of Stores | branches	500
Cash Acquired from Acquisition	$ (1,652)
Atlanta Electrical Distributors, LLC (AED) [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition	Mar. 14, 2016
Business Acquisition, Name of Acquired Entity	Atlanta Electrical Distributors, LLC ("AED")
Business Acquisition, Revenue Reported by Acquired Entity for Last Annual Period	$ 85,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	13,700
Goodwill, Acquired During Period	$ 41,100
Number of Stores	5
Hill Country Electric Supply [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition			May 1, 2015
Business Acquisition, Name of Acquired Entity			Hill Country Electric Supply, LP
Business Acquisition, Revenue Reported by Acquired Entity for Last Annual Period			$ 140,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill			21,100
Goodwill, Acquired During Period			$ 15,800
Number of Stores			9
Needham Electric Supply Corporation [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition			Oct. 30, 2015
Business Acquisition, Name of Acquired Entity			Needham Electric Supply Corporation
Business Acquisition, Revenue Reported by Acquired Entity for Last Annual Period			$ 115,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill			31,000
Goodwill, Acquired During Period			$ 35,700
Number of Stores			24
Customer Relationships [Member] | Hill Country Electric Supply [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired			$ 13,100
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			11 years
Customer Relationships [Member] | Needham Electric Supply Corporation [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired			$ 24,500
Noncompete Agreements [Member] | Hill Country Electric Supply [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired			$ 200
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			5 years
Trademarks [Member] | Hill Country Electric Supply [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired			$ 7,800
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			12 years
Trademarks [Member] | Needham Electric Supply Corporation [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired			$ 6,500
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			13 years
Minimum [Member] | Customer Relationships [Member] | Needham Electric Supply Corporation [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			12 years
Maximum [Member] | Customer Relationships [Member] | Needham Electric Supply Corporation [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			14 years

SCHEDULE OF SHARE-BASED COMPENS

SCHEDULE OF SHARE-BASED COMPENSATION, STOCK OPTIONS AND STOCK APPRECIATION RIGHTS AWARD ACTIVITY (Details) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Share-based Compensation Arrangement By Share-based Payment Award, Options and Stock Appreciation Rights, Outstanding [Roll Forward]
Weighted Average Exercise Price, Exercises in Period (in dollars per share)	$ 0
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 42.50
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	$ 23,021,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$ 51.86		$ 54.47
Share-based Compensation Arrangement By Share-based Payment Award, Options and Stock Appreciation Rights, Outstanding [Roll Forward]
Beginning of Year (in shares)	2,269,315
Grants in Period (in shares)	703,510	394,182
Exercises in Period (in shares)	0
Forfeitures in Period (in shares)	5,490
Weighted Average Exercise Price, Forfeitures in Period (in dollars per share)	$ 67.15
Weighted Average Exercise Price, Exercisable (in dollars per share)	$ 52.01
Weighted Average Remaining Contractual Term, Outstanding (in years)	5 years 6 months
Weighted Average Remaining Contractual Term, Exercisable (in years)	3 years 8 months 12 days
Aggregate Intrinsic Value, Outstanding	$ 31,627,000
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number	3,265,041		2,567,021

SCHEDULE OF SHARE-BASED PAYMENT

SCHEDULE OF SHARE-BASED PAYMENT AWARD, VALUATION ASSUMPTIONS (Details) - $ / shares	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate	1.20%	1.60%
Expected life (in years)	5 years	5 years
WESCO expected volatility	32.00%	32.00%
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	703,510	394,182
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 13	$ 21.68
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	143,168	78,292
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 42.44	$ 69.54
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	91,768	59,661
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 47	$ 67.81
Risk free interest rate	0.00%
WESCO expected volatility	0.00%

SUMMARY OF RESTRICTED STOCK UNI

SUMMARY OF RESTRICTED STOCK UNITS (Details) - Restricted Stock Units (RSUs) [Member] - $ / shares	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Unvested (in shares)	267,289		175,411
Granted (in shares)	143,168	78,292
Vested (in shares)	(50,830)
Forfeited (in shares)	(460)
Unvested, Weighted Average Fair Value (in dollars per share)	$ 57.78		$ 74.52
Granted, Weighted Average Fair Value (in dollars per share)	42.44	$ 69.54
Vested in Period, Weighted Average Fair Value (in dollars per share)	73.08
Forfeited in Period, Weighted Average Fair Value (in dollars per share)	$ 78.05

SUMMARY OF PERFORMANCE-BASED AW

SUMMARY OF PERFORMANCE-BASED AWARDS (Details) - $ / shares	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Unvested (in shares)	172,514		114,520
Granted (in shares)	91,768	59,661
Vested (in shares)	0
Forfeited (in shares)	(33,774)
Unvested, Weighted Average Fair Value (in dollars per share)	$ 60.43		$ 76.48
Granted, Weighted Average Fair Value (in dollars per share)	47	$ 67.81
Vested in Period, Weighted Average Fair Value (in dollars per share)	0
Forfeited in Period, Weighted Average Fair Value (in dollars per share)	$ 78.37
Share-based Compensation Award, Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Unvested (in shares)	86,257

SCHEDULE OF SHARE-BASED PAYME33

SCHEDULE OF SHARE-BASED PAYMENT AWARD, PERFORMANCE-BASED AWARDS, VALUATION ASSUMPTIONS (Details) - $ / shares	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Feb. 16, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
WESCO expected volatility	32.00%	32.00%
Risk free interest rate	1.20%	1.60%
Correlation	0.00%
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Exercise Price			$ 42.44
WESCO expected volatility	0.00%
Risk free interest rate	0.00%

STOCK-BASED COMPENSATION (Detai

STOCK-BASED COMPENSATION (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended	12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 3.6	$ 3.8
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	2.2	7.7
Total unrecognized compensation cost	30.5
Tax benefit associated with exercise of awards	$ 0.8	$ 2.6
Share-based Compensation Award, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance-based awards outstanding (in shares)	86,257
Performance-based Awards - Peer Group Total Shareholder Return [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance-based awards outstanding (in shares)	86,257
Scenario, Forecast [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ 11.4	$ 0.8	$ 6.8	$ 11.5

SCHEDULE OF EARNINGS PER SHARE,

SCHEDULE OF EARNINGS PER SHARE, BASIC AND DILUTED (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Earnings Per Share [Abstract]
Net income (loss) attributable to WESCO International, Inc.	$ 36,053	$ 47,031
Weighted average common shares outstanding used in computing basic earnings per share (in shares)	42,210	44,406
Common shares issuable upon exercise of dilutive stock options (in shares)	414	824
Common shares issuable from contingently convertible debentures (in shares)	4,189	6,966
Weighted average common shares outstanding and common share equivalents used in computing diluted earnings per share (in shares)	46,813	52,196
Earnings Per Share, Basic and Diluted [Abstract]
Basic (in dollars per share)	$ 0.85	$ 1.06
Diluted (in dollars per share)	$ 0.77	$ 0.90

EARNINGS PER SHARE (Details)

EARNINGS PER SHARE (Details) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Earnings Per Share Dilution Limit (in shares)	4,189,000	6,966,000
Convertible Debt Securities [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Debt Instrument, Convertible, Conversion Price (in dollars per share)	$ 28.87
Earnings Per Share Dilution Limit (in shares)	11,947,533
Dilutive Securities, Effect on Basic Earnings Per Share	$ 0.08	$ 0.14
Equity Award [Domain]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	2,300,000	900,000

EARNINGS PER SHARE Accelerated

EARNINGS PER SHARE Accelerated Share Repurchase (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Accelerated Share Repurchases [Line Items]
Payments for Repurchase of Common Stock	$ (668)	$ (27,602)
Stock Repurchase Program, Authorized Amount	$ 300,000
Repurchase Agreements [Member]
Accelerated Share Repurchases [Line Items]
Payments for Repurchase of Common Stock			$ (150,000)
Treasury Stock, Shares, Acquired		300,651	2,468,576

EMPLOYEE BENEFIT PLANS (Details

EMPLOYEE BENEFIT PLANS (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Defined Benefit Plan, Contributions by Employer	$ 0.5
Schedule of Employee Benefit Plans [Line Items]
Postemployment Benefits, Period Expense	$ 8.3	$ 5.1
CANADA | Minimum [Member]
Schedule of Employee Benefit Plans [Line Items]
Defined Contribution Plan Employer Matching Contribution Percent	3.00%
CANADA | Maximum [Member]
Schedule of Employee Benefit Plans [Line Items]
Defined Contribution Plan Employer Matching Contribution Percent	5.00%
UNITED STATES
Schedule of Employee Benefit Plans [Line Items]
Defined Contribution Plan Employer Matching Contribution Percent	50.00%
Defined Contribution Plan Maximum Annual Contribution Per Employee Percent	6.00%

EMPLOYEE BENEFIT PLANS EMPLOYEE

EMPLOYEE BENEFIT PLANS EMPLOYEE BENEFIT PLANS Pension Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Defined Benefit Plan, Contributions by Employer	$ 500
Service cost	923	$ 1,171
Interest cost	926	1,042
Expected return on plan assets	(1,279)	(1,366)
Defined Benefit Plan, Actuarial Gain (Loss)	(10)	(4)
Net periodic benefit cost	$ 560	$ 843

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Income Tax Contingency [Line Items]
Effective tax rate	31.90%	29.41274%
Federal statutory rate	35.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Domestic, Percent	340.00%
Unrecognized Tax Benefits	$ 2,300,000
Unrecognized Tax Benefits	3,100,000
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	4,500,000
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	1,000,000
Settlement with Taxing Authority [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 300,000

OTHER FINANCIAL INFORMATION (De

OTHER FINANCIAL INFORMATION (Details) $ in Millions	Mar. 31, 2016USD ($)
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	5.375%
Convertible Senior Debentures Due in 2029 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 344.9
Senior Notes due 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 500

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Condensed Financial Information [Line Items]
Cash and cash equivalents	$ 147,834	$ 160,279	$ 154,351	$ 128,319
Trade accounts receivable, net	1,091,504	1,075,257
Inventories, net	844,106	810,067
Prepaid Expense and Other Assets, Current	131,906	122,234
Total current assets	2,274,442	2,257,534
Property, buildings and equipment, net	167,539	166,739
Intangible assets, net	421,716	403,649
Goodwill and other intangibles, net	1,762,693	1,681,662	1,675,581	1,735,440
Other assets	64,438	60,142
Total assets	4,690,828	4,569,726
Accounts payable	734,911	715,519
Short-term debt	48,251	43,314
Total current liabilities	983,302	947,801
Total stockholders' equity	1,897,804	1,776,672
Stockholders' Equity Attributable to Noncontrolling Interest	4,322	2,801
Total liabilities and stockholders' equity	4,690,828	4,569,726
Parent Company [Member]
Condensed Financial Information [Line Items]
Cash and cash equivalents	0	0	0	0
Trade accounts receivable, net	0	0
Inventories, net	0	0
Prepaid Expense and Other Assets, Current	8	15
Total current assets	8	15
Intercompany receivables, net	0	0
Property, buildings and equipment, net	0	0
Intangible assets, net	0	0
Goodwill and other intangibles, net	0	0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	3,429,718	3,309,006
Other assets	0	0
Total assets	3,429,726	3,309,021
Accounts payable	0	0
Short-term debt	0	0
Other Liabilities, Current	10,082	15,254
Total current liabilities	10,082	15,254
Intercompany payables, net	1,323,843	1,320,240
Long-term debt	178,896	177,753
Liabilities, Other than Long-term Debt, Noncurrent	19,101	19,102
Total stockholders' equity	1,897,804	1,776,672
Stockholders' Equity Attributable to Noncontrolling Interest	0	0
Total liabilities and stockholders' equity	3,429,726	3,309,021
Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Cash and cash equivalents	36,166	38,963	39,584	32,508
Trade accounts receivable, net	0	0
Inventories, net	393,120	376,641
Prepaid Expense and Other Assets, Current	34,281	47,290
Total current assets	463,567	462,894
Intercompany receivables, net	0	0
Property, buildings and equipment, net	54,688	56,921
Intangible assets, net	3,909	4,072
Goodwill and other intangibles, net	255,251	255,251
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	3,900,638	3,827,069
Other assets	23,745	32,601
Total assets	4,701,798	4,638,808
Accounts payable	404,468	414,524
Short-term debt	0	0
Other Liabilities, Current	62,450	55,129
Total current liabilities	466,918	469,653
Intercompany payables, net	607,702	644,608
Long-term debt	717,869	737,490
Liabilities, Other than Long-term Debt, Noncurrent	226,601	216,515
Total stockholders' equity	2,682,708	2,570,542
Stockholders' Equity Attributable to Noncontrolling Interest	0	0
Total liabilities and stockholders' equity	4,701,798	4,638,808
Non-Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Cash and cash equivalents	111,668	121,316	114,767	95,811
Trade accounts receivable, net	1,091,504	1,075,257
Inventories, net	450,986	433,426
Prepaid Expense and Other Assets, Current	165,680	173,596
Total current assets	1,819,838	1,803,595
Intercompany receivables, net	1,931,545	1,964,848
Property, buildings and equipment, net	112,851	109,818
Intangible assets, net	417,807	399,577
Goodwill and other intangibles, net	1,507,442	1,426,411
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0	0
Other assets	40,693	27,541
Total assets	5,830,176	5,731,790
Accounts payable	330,443	300,995
Short-term debt	48,251	43,314
Other Liabilities, Current	136,579	127,555
Total current liabilities	515,273	471,864
Intercompany payables, net	0	0
Long-term debt	494,462	523,819
Liabilities, Other than Long-term Debt, Noncurrent	177,115	173,375
Total stockholders' equity	4,647,648	4,565,533
Stockholders' Equity Attributable to Noncontrolling Interest	4,322	2,801
Total liabilities and stockholders' equity	5,830,176	5,731,790
Consolidation, Eliminations [Member]
Condensed Financial Information [Line Items]
Cash and cash equivalents	0	0	0	0
Trade accounts receivable, net	0	0
Inventories, net	0	0
Prepaid Expense and Other Assets, Current	(8,971)	(8,970)
Total current assets	(8,971)	(8,970)
Intercompany receivables, net	(1,931,545)	(1,964,848)
Property, buildings and equipment, net	0	0
Intangible assets, net	0	0
Goodwill and other intangibles, net	0	0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	(7,330,356)	(7,136,075)
Other assets	0	0
Total assets	(9,270,872)	(9,109,893)
Accounts payable	0	0
Short-term debt	0	0
Other Liabilities, Current	(8,971)	(8,970)
Total current liabilities	(8,971)	(8,970)
Intercompany payables, net	(1,931,545)	(1,964,848)
Long-term debt	0	0
Liabilities, Other than Long-term Debt, Noncurrent	0	0
Total stockholders' equity	(7,330,356)	(7,136,075)
Stockholders' Equity Attributable to Noncontrolling Interest	0	0
Total liabilities and stockholders' equity	(9,270,872)	(9,109,893)
Consolidated Entities [Member]
Condensed Financial Information [Line Items]
Cash and cash equivalents	147,834	160,279	$ 154,351	$ 128,319
Trade accounts receivable, net	1,091,504	1,075,257
Inventories, net	844,106	810,067
Prepaid Expense and Other Assets, Current	190,998	211,931
Total current assets	2,274,442	2,257,534
Intercompany receivables, net	0	0
Property, buildings and equipment, net	167,539	166,739
Intangible assets, net	421,716	403,649
Goodwill and other intangibles, net	1,762,693	1,681,662
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0	0
Other assets	64,438	60,142
Total assets	4,690,828	4,569,726
Accounts payable	734,911	715,519
Short-term debt	48,251	43,314
Other Liabilities, Current	200,140	188,968
Total current liabilities	983,302	947,801
Intercompany payables, net	0	0
Long-term debt	1,391,227	1,439,062
Liabilities, Other than Long-term Debt, Noncurrent	422,817	408,992
Total stockholders' equity	1,897,804	1,776,672
Stockholders' Equity Attributable to Noncontrolling Interest	4,322	2,801
Total liabilities and stockholders' equity	$ 4,690,828	$ 4,569,726

CONDENSED CONSOLIDATED INCOME S

CONDENSED CONSOLIDATED INCOME STATEMENTS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Condensed Financial Information [Line Items]
Net sales	$ 1,775,961	$ 1,816,330
Cost of goods sold	1,420,793	1,448,639
Selling, general and administrative expense	269,286	264,585
Depreciation and amortization	16,374	15,921
Provision for income taxes	16,145	19,498
Net income (loss)	34,534	46,793
Less: Net (loss) income attributable to noncontrolling interest	(1,519)	(238)
Net income (loss) attributable to WESCO International, Inc.	36,053	47,031
Comprehensive Income:
Foreign currency translation adjustment	82,270	(113,814)
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	(16)	0
Comprehensive income attributable to WESCO International, Inc.	118,307	(66,783)
Parent Company [Member]
Condensed Financial Information [Line Items]
Net sales	0	0
Cost of goods sold	0	0
Selling, general and administrative expense	(378)	8
Depreciation and amortization	0	0
Income (Loss) from Subsidiaries, before Tax	38,459	51,165
Interest Income (Expense), Net	(6,318)	(6,187)
Provision for income taxes	(2,015)	(1,822)
Net income (loss)	34,534	46,792
Less: Net (loss) income attributable to noncontrolling interest	0	0
Net income (loss) attributable to WESCO International, Inc.	34,534	46,792
Comprehensive Income:
Foreign currency translation adjustment	82,270	(113,814)
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	(16)
Comprehensive income attributable to WESCO International, Inc.	116,788	(67,022)
Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Net sales	800,490	839,282
Cost of goods sold	639,673	669,806
Selling, general and administrative expense	80,208	136,411
Depreciation and amortization	5,106	4,834
Income (Loss) from Subsidiaries, before Tax	(8,684)	36,268
Interest Income (Expense), Net	(18,859)	(18,640)
Provision for income taxes	18,046	2,821
Net income (loss)	29,914	43,038
Less: Net (loss) income attributable to noncontrolling interest	0	0
Net income (loss) attributable to WESCO International, Inc.	29,914	43,038
Comprehensive Income:
Foreign currency translation adjustment	82,270	(113,814)
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	(16)
Comprehensive income attributable to WESCO International, Inc.	112,168	(70,776)
Non-Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Net sales	1,000,045	1,005,250
Cost of goods sold	805,694	807,035
Selling, general and administrative expense	189,456	128,166
Depreciation and amortization	11,268	11,087
Income (Loss) from Subsidiaries, before Tax	0	0
Interest Income (Expense), Net	(6,348)	(3,933)
Provision for income taxes	114	18,499
Net income (loss)	(139)	44,396
Less: Net (loss) income attributable to noncontrolling interest	(1,519)	(238)
Net income (loss) attributable to WESCO International, Inc.	1,380	44,634
Comprehensive Income:
Foreign currency translation adjustment	82,270	(113,814)
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	(16)
Comprehensive income attributable to WESCO International, Inc.	83,634	(69,180)
Consolidation, Eliminations [Member]
Condensed Financial Information [Line Items]
Net sales	(24,574)	(28,202)
Cost of goods sold	(24,574)	(28,202)
Selling, general and administrative expense	0	0
Depreciation and amortization	0	0
Income (Loss) from Subsidiaries, before Tax	(29,775)	(87,433)
Interest Income (Expense), Net	0	0
Provision for income taxes	0	0
Net income (loss)	(29,775)	(87,433)
Less: Net (loss) income attributable to noncontrolling interest	0	0
Net income (loss) attributable to WESCO International, Inc.	(29,775)	(87,433)
Comprehensive Income:
Foreign currency translation adjustment	(164,540)	227,628
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	32
Comprehensive income attributable to WESCO International, Inc.	(194,283)	140,195
Consolidated Entities [Member]
Condensed Financial Information [Line Items]
Net sales	1,775,961	1,816,330
Cost of goods sold	1,420,793	1,448,639
Selling, general and administrative expense	269,286	264,585
Depreciation and amortization	16,374	15,921
Income (Loss) from Subsidiaries, before Tax	0	0
Interest Income (Expense), Net	18,829	(20,894)
Provision for income taxes	16,145	19,498
Net income (loss)	34,534	46,793
Less: Net (loss) income attributable to noncontrolling interest	(1,519)	(238)
Net income (loss) attributable to WESCO International, Inc.	36,053	47,031
Comprehensive Income:
Foreign currency translation adjustment	82,270	(113,814)
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	(16)
Comprehensive income attributable to WESCO International, Inc.	$ 118,307	$ (66,783)

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENT OF CASH FLOWS (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	$ (8,148)	$ 785
Net cash (used) provided by operating activities	78,568	90,056
Investing Activities:
Capital expenditures	(3,608)	(5,026)
Acquisition payments	(50,348)	0
Net cash used in investing activities	(62,104)	(4,241)
Financing Activities:
Proceeds from (Repayments of) Bank Overdrafts	11,972	(6,725)
Payments for Repurchase of Common Stock	(668)	(27,602)
Proceeds from (Payments for) Other Financing Activities	(209)	(484)
Net cash used in financing activities	(34,774)	(53,791)
Effect of exchange rate changes on cash and cash equivalents	5,865	(5,992)
Net change in cash and cash equivalents	(12,445)	26,032
Cash and cash equivalents at the beginning of period	160,279	128,319	$ 128,319
Cash and cash equivalents at the end of period	147,834	154,351	160,279
Parent Company [Member]
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	0	0
Net cash (used) provided by operating activities	(3,138)	(4,441)
Investing Activities:
Capital expenditures	0	0
Acquisition payments	0
Proceeds from Dividends Received	0	0
Net cash used in investing activities	0	0
Financing Activities:
Borrowings	3,603	32,125
Repayments	0	0
Proceeds from (Repayments of) Bank Overdrafts	0	0
Cash Dividends Paid to Parent Company	0	0
Payments for Repurchase of Common Stock		(27,602)
Proceeds from (Payments for) Other Financing Activities	(465)	(82)
Net cash used in financing activities	3,138	4,441
Effect of exchange rate changes on cash and cash equivalents	0	0
Net change in cash and cash equivalents	0	0
Cash and cash equivalents at the beginning of period	0	0	0
Cash and cash equivalents at the end of period	0	0	0
Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	(14,548)	(43,850)
Net cash (used) provided by operating activities	62,678	53,333
Investing Activities:
Capital expenditures	(3,084)	(4,005)
Acquisition payments	(50,348)
Proceeds from Dividends Received	15,310	16,090
Net cash used in investing activities	(52,670)	(31,765)
Financing Activities:
Borrowings	284,972	218,699
Repayments	(309,337)	(226,064)
Proceeds from (Repayments of) Bank Overdrafts	11,972	(6,725)
Cash Dividends Paid to Parent Company	0	0
Payments for Repurchase of Common Stock		0
Proceeds from (Payments for) Other Financing Activities	(412)	(402)
Net cash used in financing activities	(12,805)	(14,492)
Effect of exchange rate changes on cash and cash equivalents	0	0
Net change in cash and cash equivalents	(2,797)	7,076
Cash and cash equivalents at the beginning of period	38,963	32,508	32,508
Cash and cash equivalents at the end of period	36,166	39,584	38,963
Non-Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	(3,783)	5,150
Net cash (used) provided by operating activities	19,028	41,164
Investing Activities:
Capital expenditures	(524)	(1,021)
Acquisition payments	0
Proceeds from Dividends Received	0	0
Net cash used in investing activities	(4,307)	4,129
Financing Activities:
Borrowings	69,969	162,325
Repayments	(84,893)	(166,580)
Proceeds from (Repayments of) Bank Overdrafts	0	0
Cash Dividends Paid to Parent Company	(15,310)	(16,090)
Payments for Repurchase of Common Stock		0
Proceeds from (Payments for) Other Financing Activities	0	0
Net cash used in financing activities	(30,234)	(20,345)
Effect of exchange rate changes on cash and cash equivalents	5,865	(5,992)
Net change in cash and cash equivalents	(9,648)	18,956
Cash and cash equivalents at the beginning of period	121,316	95,811	95,811
Cash and cash equivalents at the end of period	111,668	114,767	121,316
Consolidation, Eliminations [Member]
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	10,183	39,485
Net cash (used) provided by operating activities	0	0
Investing Activities:
Capital expenditures	0	0
Acquisition payments	0
Proceeds from Dividends Received	(15,310)	(16,090)
Net cash used in investing activities	(5,127)	23,395
Financing Activities:
Borrowings	(14,548)	(43,850)
Repayments	(4,365)	(4,365)
Proceeds from (Repayments of) Bank Overdrafts	0	0
Cash Dividends Paid to Parent Company	(15,310)	(16,090)
Payments for Repurchase of Common Stock		0
Proceeds from (Payments for) Other Financing Activities	0	0
Net cash used in financing activities	5,127	(23,395)
Effect of exchange rate changes on cash and cash equivalents	0	0
Net change in cash and cash equivalents	0	0
Cash and cash equivalents at the beginning of period	0	0	0
Cash and cash equivalents at the end of period	0	0	0
Consolidated Entities [Member]
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	(8,148)	785
Net cash (used) provided by operating activities	78,568	90,056
Investing Activities:
Capital expenditures	(3,608)	(5,026)
Acquisition payments	(50,348)
Proceeds from Dividends Received	0	0
Net cash used in investing activities	(62,104)	(4,241)
Financing Activities:
Borrowings	343,996	369,299
Repayments	(389,865)	(388,279)
Proceeds from (Repayments of) Bank Overdrafts	11,972	(6,725)
Cash Dividends Paid to Parent Company	0	0
Payments for Repurchase of Common Stock		(27,602)
Proceeds from (Payments for) Other Financing Activities	(877)	(484)
Net cash used in financing activities	(34,774)	(53,791)
Effect of exchange rate changes on cash and cash equivalents	5,865	(5,992)
Net change in cash and cash equivalents	(12,445)	26,032
Cash and cash equivalents at the beginning of period	160,279	128,319	128,319
Cash and cash equivalents at the end of period	$ 147,834	$ 154,351	$ 160,279

Subsequent Events (Details)

Subsequent Events (Details) - Needham Electric Supply Corporation [Member] $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)
Subsequent Event [Line Items]
Business Acquisition, Effective Date of Acquisition	Oct. 30, 2015
Business Acquisition, Revenue Reported by Acquired Entity for Last Annual Period	$ 115

GOODWILL (Details)

GOODWILL (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2014
Goodwill [Line Items]
Goodwill	$ 1,762,693	$ 1,675,581	$ 1,681,662	$ 1,735,440
Goodwill, Foreign Currency Translation Gain (Loss)	39,918	(59,859)
Goodwill, Acquired During Period	$ 41,113	$ 0