WESCO International (WCC) 10-Q 4 Aug 17 2017 Q2 Quarterly report Financial data

DOCUMENT AND ENTITY INFORMATION

DOCUMENT AND ENTITY INFORMATION Document - shares	6 Months Ended
	Jun. 30, 2017	Aug. 03, 2017
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	Jun. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Common Stock, Shares Outstanding		47,973,171

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Dec. 31, 2016USD ($)
Depreciation, Depletion and Amortization, Nonproduction	$ 15,721	$ 31,686
Other Accrued Liabilities, Current	102,851	102,851	$ 111,304
Current Assets:
Cash and cash equivalents	87,799	87,799	110,131
Allowance for Doubtful Accounts Receivable, Current	23,061	23,061	22,007
Trade accounts receivable, net of allowance for doubtful accounts of $23,069 and $19,309 in 2014 and 2013, respectively	1,144,978	1,144,978	1,034,402
Accounts and Other Receivables, Net, Current	69,321	69,321	85,019
Inventories, net	866,301	866,301	821,441
Prepaid expenses and other current assets	137,146	137,146	121,464
Total current assets	2,305,545	2,305,545	2,172,457
Property, buildings and equipment, net of accumulated depreciation of $229,041 and $213,758 in 2014 and 2013, respectively	155,203	155,203	157,607
Intangible assets, net	380,426	380,426	393,362
Goodwill	1,741,540	1,741,540	1,720,714
Other assets	40,957	40,957	46,844
Total assets	4,623,671	4,623,671	4,490,984
Current Liabilities:
Accounts payable	768,997	768,997	684,721
Accrued payroll and benefit costs	37,830	37,830	49,250
Short-term debt	23,972	23,972	20,920
Current portion of long-term debt	1,221	1,221	1,218
Total current liabilities	964,406	964,406	896,797
Long-term Debt, Excluding Current Maturities	1,334,542	1,334,542	1,363,135
Other noncurrent liabilities	63,928	63,928	63,031
Deferred income taxes	165,689	165,689	158,009
Total liabilities	2,528,565	2,528,565	2,480,972
Commitments and Contingencies
Bank Overdrafts	29,535	29,535	29,384
Stockholders' Equity:
Preferred stock, $.01 par value; 20,000,000 shares authorized, no shares issued or outstanding	0	0	0
Additional capital	991,750	991,750	986,020
Retained earnings	2,044,719	2,044,719	1,956,532
Treasury stock, at cost; 18,247,467 and 18,179,275 shares in 2014 and 2013, respectively	(596,659)	(596,659)	(542,537)
Accumulated other comprehensive income	(342,164)	(342,164)	(387,365)
Total WESCO International stockholders' equity	2,095,106	2,095,106	2,010,012
Noncontrolling interest	(3,173)	(3,173)	(3,269)
Total stockholders' equity	2,098,279	2,098,279	2,013,281
Total liabilities and stockholders' equity	4,623,671	4,623,671	4,490,984
Common Stock [Member]
Stockholders' Equity:
Common stock	590	590	588
Common Class B [Member]
Stockholders' Equity:
Common stock	$ 43	$ 43	$ 43

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parentheticals) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Allowance for doubtful accounts	$ 23,061,000	$ 22,007,000
Accumulated depreciation	268,723,000	259,126,000
Finite-Lived Intangible Assets, Accumulated Amortization	200,755	178,813
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ 15,291,000	$ 17,278,000
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)	15,400,907	14,545,715
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)	59,033,859	58,817,781
Common stock, shares outstanding (in shares)	47,972,383	48,611,497
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		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Statement [Abstract]
Net sales	$ 1,909,624	$ 1,911,582	$ 3,682,215	$ 3,687,543
Cost of goods sold	1,543,510	1,532,113	2,966,083	2,952,906
Selling, general and administrative expense	267,288	274,523	534,252	543,809
Depreciation and amortization	15,721	16,959	31,686	33,332
Income from operations	83,105	87,987	150,194	157,496
Interest expense, net	16,816	19,452	33,537	38,281
Income before income taxes	66,289	68,535	116,657	119,215
Provision for income taxes	16,754	18,683	29,323	34,828
Net income	49,535	49,852	87,334	84,387
Net (loss) income attributable to noncontrolling interest	25	54	96	(1,465)
Net income attributable to WESCO International, Inc.	49,510	49,798	87,238	85,852
Comprehensive Income:
Foreign currency translation adjustment	33,381	(1,765)	44,949	80,505
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	0	0	252	(16)
Comprehensive income attributable to WESCO International, Inc.	$ 82,891	$ 48,033	$ 132,439	$ 166,341
Earnings per share attributable to WESCO International, Inc.
Basic (in dollars per share)	$ 1.03	$ 1.18	$ 1.80	$ 2.03
Diluted (in dollars per share)	$ 1.02	$ 1.02	$ 1.78	$ 1.79

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Operating Activities:
Net income	$ 87,334	$ 84,387
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	31,686	33,332
Deferred income taxes	6,404	13,425
Other operating activities, net	8,306	10,393
Changes in assets and liabilities
Increase (Decrease) in Accounts Receivable	95,978	17,250
Increase (Decrease) in Accounts and Other Receivables	(16,425)	(29,442)
Inventories, net	(36,877)	(4,377)
Prepaid expenses and other current assets	(6,360)	(12,775)
Accounts payable	76,836	(18,782)
Accrued payroll and benefit costs	(10,786)	(2,559)
Other current and noncurrent liabilities	(10,221)	23,374
Net cash provided by operating activities	66,769	138,610
Investing Activities:
Capital expenditures	(9,795)	(7,086)
Acquisition payments, net of cash acquired	0	(50,946)
Other investing activities	3,467	(8,103)
Net cash used in investing activities	(6,328)	(66,135)
Financing Activities:
Proceeds from issuance of short-term debt	69,257	63,745
Repayments of short-term debt	(68,517)	(62,937)
Proceeds from issuance of long-term debt	662,078	1,026,392
Repayments of Long-term Debt	(692,078)	(1,102,792)
Other financing activities, net	(768)	(6,322)
Net cash used in financing activities	(86,538)	(76,180)
Payments for Repurchase of Common Stock	(56,665)	(740)
Proceeds from (Repayments of) Bank Overdrafts	155	6,474
Effect of exchange rate on cash and cash equivalents	3,765	3,716
Net change in cash and cash equivalents	(22,332)	11
Cash and cash equivalents at the beginning of period	110,131	160,279
Cash and cash equivalents at the end of period	$ 87,799	$ 160,290

ORGANIZATION

ORGANIZATION	6 Months Ended
	Jun. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
ORGANIZATION	1. ORGANIZATION WESCO International, Inc. ("WESCO International") 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 manufacturer (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 approximately 75,000 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	6 Months Ended
	Jun. 30, 2017
Accounting Policies [Abstract]
ACCOUNTING POLICIES	2. 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 2016 Annual Report on Form 10-K as filed with the SEC on February 22, 2017. The Condensed Consolidated Balance Sheet at December 31, 2016 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 June 30, 2017 , the unaudited Condensed Consolidated Statements of Income and Comprehensive Income for the six months ended June 30, 2017 and 2016 , respectively, and the unaudited Condensed Consolidated Statements of Cash Flows for the six months ended June 30, 2017 and 2016 , 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. Recently Adopted Accounting Pronouncements In March 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (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. The Company adopted this ASU in the first quarter of 2017. The amendment related to the recognition of excess tax benefits and deficiencies was applied prospectively and, as disclosed in Note 9, lowered the Company's effective tax rate for the six months ended June 30, 2017 . The amendment related to the presentation of excess tax benefits on the statement of cash flows was also applied prospectively, and did not have a material impact on WESCO's cash flows. The other amendments, which were adopted by the Company according to the respective transition requirements, had no impact on the consolidated financial statements and notes thereto. In October 2016, the FASB issued ASU 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory. The purpose of ASU 2016-16 is to simplify the income tax accounting of an intra-entity transfer of an asset other than inventory and to record its effect when the transfer occurs. The Company early adopted this ASU on a modified retrospective basis in the first quarter of 2017. 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. During 2016, the FASB issued four ASUs that address implementation issues and correct or improve certain aspects of the new revenue recognition guidance, including ASU 2016-08, Principal versus Agent Considerations (Reporting Revenue Gross versus Net) , ASU 2016-10, Identifying Performance Obligations and Licensing , ASU 2016-12, Narrow-Scope Improvements and Practical Expedients and ASU 2016-20, Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers . These ASUs do not change the core principles in the revenue recognition standard outlined above. The Company has developed a multiphase plan and established a cross-functional team to evaluate and implement the new standard. Management is in the process of completing the diagnostic phase. In this phase, management is reviewing various customer contracts and comparing current accounting and disclosure policies to the requirements of the new standard. Management expects to adopt the new standard using the modified retrospective approach in the first quarter of 2018. The method of adoption is subject to change as management continues to evaluate the impact that this pronouncement may have 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 June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , which introduces new guidance for the accounting for credit losses on certain financial instruments. The amendments in ASU 2016-13 are effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years and early adoption is permitted. Management is currently evaluating the impact of this accounting standard on WESCO's consolidated financial statements and notes thereto. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (a consensus of the Emerging Issues Task Force) . This ASU provides guidance on eight specific cash flow issues where there is diversity in practice. The amendments in this ASU are effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted, including adoption in an interim period. Management is currently evaluating the impact of this accounting standard on WESCO's consolidated financial statements and notes thereto. In January 2017, the FASB issued ASU 2017-04, Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment, which eliminates Step 2 from the goodwill impairment test. Under the amendments in this update, an entity should perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. An entity should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. An entity should apply the amendments in this ASU on a prospective basis. This guidance is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Management has not yet evaluated the impact of this accounting standard on WESCO's consolidated financial statements and notes thereto. In March 2017, the FASB issued ASU 2017-07, Compensation—Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost . Presently, net benefit cost is reported as an employee cost within operating income (or capitalized into assets when appropriate). This amendment requires the bifurcation of net benefit cost. The service component will be presented with other employee compensation costs in operating income (or capitalized in assets). The other components will be reported separately outside of operations, and will not be eligible for capitalization. This guidance is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Early adoption is permitted. Management has not yet evaluated the impact of this accounting standard on WESCO's consolidated financial statements and notes thereto. In May 2017, the FASB issued ASU 2017-09, Compensation—Stock Compensation (Topic 718): Scope of Modification Accounting , which clarifies when to account for a change to the terms or conditions of a share-based payment award as a modification. Under the new guidance, modification accounting is required only if the fair value, the vesting conditions, or the classification of the award (as equity or liability) changes as a result of the change in terms or conditions. The guidance is effective prospectively for all companies for annual periods beginning on or after December 15, 2017. Early adoption is permitted. Management has not yet evaluated 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. Fair Value of Financial Instruments The Company’s financial instruments consist of cash and cash equivalents, accounts receivable, accounts payable and other accrued liabilities, and outstanding indebtedness. The reported carrying amounts of WESCO’s financial 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.

ACQUISITIONS

ACQUISITIONS	6 Months Ended
	Jun. 30, 2017
Business Combinations [Abstract]
ACQUISITIONS	3. ACQUISITIONS On March 14, 2016 , WESCO Distribution, Inc. ("WESCO Distribution") 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 Distribution 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 included 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 was accrued at the maximum potential payout under the terms of the purchase agreement. The fair value of intangibles was estimated by management and the allocation resulted in intangible assets of $21.8 million and goodwill of $30.0 million . The intangible assets include customer relationships of $15.8 million amortized over 13 and 14 years, a trademark of $6.0 million amortized over 13 years, and non-compete agreements of less than $0.1 million amortized over 5 years. No residual value was estimated for the intangible assets being amortized. The majority of goodwill is deductible for tax purposes.

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	6 Months Ended
	Jun. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
STOCK-BASED COMPENSATION	5. 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 and six months ended June 30, 2017 and 2016 , 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 Six Months Ended June 30, June 30, June 30, June 30, Stock-settled stock appreciation rights granted — 4,744 443,731 708,254 Weighted-average fair value $ — $ 17.22 $ 20.65 $ 12.90 Restricted stock units granted — 137 98,680 143,305 Weighted-average fair value $ — $ 54.67 $ 71.65 $ 42.45 Performance-based awards granted — — 39,978 91,768 Weighted-average fair value $ — $ — $ 76.63 $ 47.00 The fair value of stock-settled stock appreciation rights was estimated using the following weighted-average assumptions: Three Months Ended Six Months Ended June 30, June 30, June 30, June 30, Risk free interest rate — % 1.2 % 1.9 % 1.2 % Expected life (in years) 0 5 5 5 Expected volatility — % 32 % 29 % 32 % The risk-free interest rate is based on the U.S. Treasury Daily Yield Curve rate 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 six months ended June 30, 2017 : Awards Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (In years) Aggregate Intrinsic Value (In thousands) Outstanding at December 31, 2016 2,439,487 $ 52.62 Granted 443,731 71.65 Exercised (468,600 ) 42.48 Forfeited (87,445 ) 68.93 Outstanding at June 30, 2017 2,327,173 57.68 6.6 $ 17,651 Exercisable at June 30, 2017 1,398,502 $ 56.84 5.0 $ 11,783 The following table sets forth a summary of time-based restricted stock units and related information for the six months ended June 30, 2017 : Awards Weighted- Average Fair Value Unvested at December 31, 2016 257,096 $ 57.47 Granted 98,680 71.65 Vested (43,169 ) 85.17 Forfeited (12,449 ) 53.91 Unvested at June 30, 2017 300,158 $ 58.29 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 six months ended June 30, 2017 : Awards Weighted- Average Fair Value Unvested at December 31, 2016 149,320 $ 60.36 Granted 39,978 76.63 Vested — — Forfeited (36,162 ) 79.64 Unvested at June 30, 2017 153,136 $ 60.05 The fair value of the performance shares granted during the six months ended June 30, 2017 and 2016 was estimated using the following weighted-average assumptions: Six Months Ended June 30, June 30, Grant date share price $ 71.65 $ 42.44 WESCO expected volatility 29 % 26 % Peer group median volatility 24 % 24 % Risk-free interest rate 1.5 % 0.9 % Correlation of peer company returns 114 % 122 % The unvested performance-based awards in the table above include 76,568 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 76,568 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 $4.1 million and $3.4 million of non-cash stock-based compensation expense, which is included in selling, general and administrative expenses, for the three months ended June 30, 2017 and 2016 , respectively. WESCO recognized $7.8 million and $7.0 million of non-cash stock-based compensation expense, which is included in selling, general and administrative expenses, for the six months ended June 30, 2017 and 2016 , respectively. As of June 30, 2017 , there was $26.4 million of total unrecognized compensation cost related to non-vested stock-based compensation arrangements for all awards previously made, of which approximately $7.5 million is expected to be recognized over the remainder of 2017 , $11.5 million in 2018 , $6.7 million in 2019 and $0.7 million in 2020 .

EARNINGS PER SHARE

EARNINGS PER SHARE	6 Months Ended
	Jun. 30, 2017
Earnings Per Share [Abstract]
EARNINGS PER SHARE	6. EARNINGS PER SHARE Basic earnings per share is computed by dividing net income attributable to WESCO International by the weighted-average number of common shares outstanding during the periods. Diluted earnings per share is computed by dividing net income attributable to WESCO International 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 equity awards and contingently convertible debt. The following table sets forth the details of basic and diluted earnings per share: Three Months Ended Six Months Ended June 30, June 30, (In thousands, except per share data) 2017 2016 2017 2016 Net income attributable to WESCO International, Inc. $ 49,510 $ 49,798 $ 87,238 $ 85,852 Weighted-average common shares outstanding used in computing basic earnings per share 48,294 42,238 48,499 42,224 Common shares issuable upon exercise of dilutive equity awards 482 569 582 494 Common shares issuable from contingently convertible debentures (see below for basis of calculation) — 5,820 — 5,120 Weighted-average common shares outstanding and common share equivalents used in computing diluted earnings per share 48,776 48,627 49,081 47,838 Earnings per share attributable to WESCO International, Inc. Basic $ 1.03 $ 1.18 $ 1.80 $ 2.03 Diluted $ 1.02 $ 1.02 $ 1.78 $ 1.79 For the three and six months ended June 30, 2017 , the computation of diluted earnings per share attributable to WESCO International, Inc. excluded stock-based awards of approximately 1.3 million and 1.2 million , respectively. For the three and six months ended June 30, 2016 , the computation of diluted earnings per share attributable to WESCO International, Inc. excluded stock-based awards of approximately 1.5 million and 2.1 million , respectively. These amounts were excluded because their effect would have been antidilutive. Because of WESCO’s previous obligation to settle the par value of the 6.0% Convertible Senior Debentures due 2029 (the "2029 Debentures") in cash upon conversion, WESCO was 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 exceeded the conversion price of the debentures. Only the number of shares that would have been issuable under the treasury stock method of accounting for share dilution were included, which was based upon the amount by which the average stock price exceeded the conversion price. The conversion price of the 2029 Debentures was $28.87 and the maximum amount of share dilution was limited to 11,951,932 shares. Since the 2029 Debentures were redeemed on September 15, 2016, there was no dilution from contingently convertible debentures for the three and six months ended June 30, 2017 . For the three and six months ended June 30, 2016 , the effect of the 2029 Debentures on diluted earnings per share attributable to WESCO International, Inc. was a decrease of $0.14 and $0.22 , 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 . As of December 31, 2016 , WESCO had repurchased 2,468,576 shares of the Company's common stock for $150.0 million under this repurchase authorization. On May 2, 2017, the Company entered into an accelerated stock repurchase agreement (the "ASR Transaction") with a financial institution to repurchase additional shares of its common stock. In exchange for an up-front cash payment of $50.0 million , the Company received 804,291 shares. The total number of shares ultimately delivered under the ASR Transaction was determined by the average of the volume-weighted average prices of the Company's common stock for each exchange business day during the settlement valuation period. WESCO funded the repurchase with available cash and borrowings under the Company's accounts receivable securitization facility. For purposes of computing earnings per share, shares received under the ASR Transaction were reflected as a reduction to common shares outstanding on the respective delivery dates.

EMPLOYEE BENEFIT PLANS

EMPLOYEE BENEFIT PLANS	6 Months Ended
	Jun. 30, 2017
Retirement Benefits [Abstract]
EMPLOYEE BENEFIT PLANS	7. 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 matches contributions made by employees at an amount equal to 50% of participants' total monthly contributions up to a maximum of 6% of eligible compensation. For Canadian participants, WESCO makes contributions in amounts ranging from 3% to 5% of the participants' eligible compensation based on years of continuous service. WESCO may also make, subject to the Board of Directors' approval, a discretionary contribution to the defined contribution retirement savings plan covering U.S. participants if certain predetermined profit levels are attained. For the six months ended June 30, 2017 and 2016 , WESCO incurred charges of $10.6 million and $18.1 million , respectively, for all such plans. Contributions are made in cash to employee retirement savings plan accounts. The deferred compensation plan is an unfunded plan. As of June 30, 2017 and December 31, 2016 , the Company's obligation under the deferred compensation plan was $22.9 million and $21.7 million , respectively. 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 defined benefit plans: Three Months Ended Six Months Ended June 30, June 30, (In thousands of dollars) 2017 2016 2017 2016 Service cost $ 1,049 $ 990 $ 2,116 $ 1,913 Interest cost 945 993 1,907 1,918 Expected return on plan assets (1,343 ) (1,372 ) (2,711 ) (2,651 ) Recognized actuarial gain (48 ) (11 ) (97 ) (20 ) Net periodic benefit cost $ 603 $ 600 $ 1,215 $ 1,160 During the three and six months ended June 30, 2017 , there were no employer contributions to the defined benefit plans. During the three and six months ended June 30, 2016 , the Company made aggregate cash contributions of $0.5 million and $1.0 million , respectively, to the defined benefit plans.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	6 Months Ended
	Jun. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	8. 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 is 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. The third party auditor has issued preliminary findings for review by the Company, 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 may issue 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 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 potential exposure at this time.

INCOME TAXES

INCOME TAXES	6 Months Ended
	Jun. 30, 2017
Income Tax Disclosure [Abstract]
INCOME TAXES	9. INCOME TAXES The effective tax rate for the three and six months ended June 30, 2017 was 25.3% and 25.1% , respectively. The effective tax rate for the three and six months ended June 30, 2016 was 27.3% and 29.2% , 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 tax rates on foreign earnings, which are partially offset by nondeductible expenses and state taxes. The current year's effective tax rate is lower than the prior year primarily due to favorable discrete items, including a benefit from the exercise and vesting of stock-based awards, as well as the mix of income earned in jurisdictions with lower tax rates. The total amount of unrecognized tax benefits was reduced by $1.5 million during the six months ended June 30, 2017 to $4.7 million due to the expiration of statutes of limitation and the settlement of state audits. At June 30, 2017 , the amount of unrecognized tax benefits that could affect the effective tax rate if recognized in the consolidated financial statements was $6.0 million . Within the next twelve months, it is reasonably possible that the amount of unrecognized tax benefits will decrease by approximately $0.3 million due to the expiration of statutes of limitation and the settlement of state audits. Of this amount, $0.1 million could impact the effective tax rate.

OTHER FINANCIAL INFORMATION

OTHER FINANCIAL INFORMATION	6 Months Ended
	Jun. 30, 2017
Condensed Financial Information [Abstract]
OTHER FINANCIAL INFORMATION	10. CONDENSED CONSOLIDATING FINANCIAL INFORMATION WESCO Distribution has outstanding $500 million in aggregate principal amount of 5.375% Senior Notes due 2021 (the "2021 Notes") and $350 million in aggregate principal amount of 5.375% Senior Notes due 2024 (the "2024 Notes"). The 2021 Notes and 2024 Notes are unsecured senior obligations of WESCO Distribution and are fully and unconditionally guaranteed on a senior unsecured basis by WESCO International. 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 June 30, 2017 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Cash and cash equivalents $ — $ 36,138 $ 51,661 $ — $ 87,799 Trade accounts receivable, net — — 1,144,978 — 1,144,978 Inventories — 379,826 486,475 — 866,301 Prepaid expenses and other current assets 13,652 24,311 212,335 (43,831 ) 206,467 Total current assets 13,652 440,275 1,895,449 (43,831 ) 2,305,545 Intercompany receivables, net — — 2,118,924 (2,118,924 ) — Property, buildings and equipment, net — 49,797 105,406 — 155,203 Intangible assets, net — 3,094 377,332 — 380,426 Goodwill — 244,648 1,496,892 — 1,741,540 Investments in affiliates 3,717,402 4,139,039 — (7,856,441 ) — Other assets — 18,615 22,342 40,957 Total assets $ 3,731,054 $ 4,895,468 $ 6,016,345 $ (10,019,196 ) $ 4,623,671 Accounts payable $ — $ 413,605 $ 355,392 $ — $ 768,997 Short-term debt — — 23,972 — 23,972 Other current liabilities — 39,699 175,569 (43,831 ) 171,437 Total current liabilities — 453,304 554,933 (43,831 ) 964,406 Intercompany payables, net 1,620,034 498,890 — (2,118,924 ) — Long-term debt, net — 958,697 375,845 — 1,334,542 Other noncurrent liabilities 12,741 49,577 167,299 — 229,617 Total WESCO International, Inc. stockholders' equity 2,098,279 2,935,000 4,921,441 (7,856,441 ) 2,098,279 Noncontrolling interests — — (3,173 ) — (3,173 ) Total liabilities and stockholders’ equity $ 3,731,054 $ 4,895,468 $ 6,016,345 $ (10,019,196 ) $ 4,623,671 Condensed Consolidating Balance Sheet December 31, 2016 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Cash and cash equivalents $ — $ 41,552 $ 68,579 $ — $ 110,131 Trade accounts receivable, net — — 1,034,402 — 1,034,402 Inventories — 364,562 456,879 — 821,441 Prepaid expenses and other current assets 13,647 24,214 225,412 (56,790 ) 206,483 Total current assets 13,647 430,328 1,785,272 (56,790 ) 2,172,457 Intercompany receivables, net — — 2,056,783 (2,056,783 ) — Property, buildings and equipment, net — 51,824 105,783 — 157,607 Intangible assets, net — 3,417 389,945 — 393,362 Goodwill — 244,648 1,476,066 — 1,720,714 Investments in affiliates 3,584,857 4,018,661 — (7,603,518 ) — Other assets — 23,846 22,998 — 46,844 Total assets $ 3,598,504 $ 4,772,724 $ 5,836,847 $ (9,717,091 ) $ 4,490,984 Accounts payable $ — $ 381,795 $ 302,926 $ — $ 684,721 Short-term debt — — 20,920 — 20,920 Other current liabilities — 53,458 194,488 (56,790 ) 191,156 Total current liabilities — 435,253 518,334 (56,790 ) 896,797 Intercompany payables, net 1,572,486 484,297 — (2,056,783 ) — Long-term debt, net — 983,449 379,686 — 1,363,135 Other noncurrent liabilities 12,737 46,476 161,827 — 221,040 Total WESCO International, Inc. stockholders' equity 2,013,281 2,823,249 4,780,269 (7,603,518 ) 2,013,281 Noncontrolling interests — — (3,269 ) — (3,269 ) Total liabilities and stockholders’ equity $ 3,598,504 $ 4,772,724 $ 5,836,847 $ (9,717,091 ) $ 4,490,984 Condensed Consolidating Statement of Income and Comprehensive Income Three Months Ended June 30, 2017 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 843,518 $ 1,100,661 $ (34,555 ) $ 1,909,624 Cost of goods sold (excluding depreciation and amortization) — 683,064 895,001 (34,555 ) 1,543,510 Selling, general and administrative expenses — 134,730 132,558 — 267,288 Depreciation and amortization — 4,583 11,138 — 15,721 Results of affiliates’ operations 49,535 40,753 — (90,288 ) — Interest expense (income), net — 28,518 (11,702 ) — 16,816 Income tax (benefit) expense — (1,862 ) 18,616 — 16,754 Net income 49,535 35,238 55,050 (90,288 ) 49,535 Net income attributable to noncontrolling interests — — 25 — 25 Net income attributable to WESCO International, Inc. $ 49,535 $ 35,238 $ 55,025 $ (90,288 ) $ 49,510 Other comprehensive income: Foreign currency translation adjustments 33,381 33,381 33,381 (66,762 ) 33,381 Comprehensive income attributable to WESCO International, Inc. $ 82,916 $ 68,619 $ 88,406 $ (157,050 ) $ 82,891 Condensed Consolidating Statement of Income and Comprehensive Income Three Months Ended June 30, 2016 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 853,028 $ 1,087,050 $ (28,496 ) $ 1,911,582 Cost of goods sold (excluding depreciation and amortization) — 682,808 877,801 (28,496 ) 1,532,113 Selling, general and administrative expenses 11 142,942 131,570 — 274,523 Depreciation and amortization — 5,098 11,861 — 16,959 Results of affiliates’ operations 54,511 42,518 — (97,029 ) — Interest expense (income), net 6,333 20,845 (7,726 ) — 19,452 Income tax (benefit) expense (1,685 ) (1,108 ) 21,476 — 18,683 Net income 49,852 44,961 52,068 (97,029 ) 49,852 Net income attributable to noncontrolling interests — — 54 — 54 Net income attributable to WESCO International, Inc. $ 49,852 $ 44,961 $ 52,014 $ (97,029 ) $ 49,798 Other comprehensive loss: Foreign currency translation adjustments (1,765 ) (1,765 ) (1,765 ) 3,530 (1,765 ) Comprehensive income attributable to WESCO International, Inc. $ 48,087 $ 43,196 $ 50,249 $ (93,499 ) $ 48,033 Condensed Consolidating Statement of Income and Comprehensive Income Six Months Ended June 30, 2017 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 1,622,129 $ 2,120,315 $ (60,229 ) $ 3,682,215 Cost of goods sold (excluding depreciation and amortization) — 1,304,812 1,721,500 (60,229 ) 2,966,083 Selling, general and administrative expenses — 269,986 264,266 — 534,252 Depreciation and amortization — 9,336 22,350 — 31,686 Results of affiliates’ operations 87,334 75,181 — (162,515 ) — Interest expense (income), net — 49,525 (15,988 ) — 33,537 Income tax (benefit) expense — (2,898 ) 32,221 — 29,323 Net income 87,334 66,549 95,966 (162,515 ) 87,334 Net income attributable to noncontrolling interests — — 96 — 96 Net income attributable to WESCO International, Inc. $ 87,334 $ 66,549 $ 95,870 $ (162,515 ) $ 87,238 Other comprehensive income: Foreign currency translation adjustments 44,949 44,949 44,949 (89,898 ) 44,949 Post retirement benefit plan adjustment 252 252 252 (504 ) 252 Comprehensive income attributable to WESCO International, Inc. $ 132,535 $ 111,750 $ 141,071 $ (252,917 ) $ 132,439 Condensed Consolidating Statement of Income and Comprehensive Income Six Months Ended June 30, 2016 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 1,653,518 $ 2,087,095 $ (53,070 ) $ 3,687,543 Cost of goods sold (excluding depreciation and amortization) — 1,322,481 1,683,495 (53,070 ) 2,952,906 Selling, general and administrative expenses (366 ) 223,149 321,026 — 543,809 Depreciation and amortization — 10,203 23,129 — 33,332 Results of affiliates’ operations 92,970 33,834 — (126,804 ) — Interest expense (income), net 12,651 39,704 (14,074 ) — 38,281 Income tax (benefit) expense (3,702 ) 16,939 21,591 — 34,828 Net income 84,387 74,876 51,928 (126,804 ) 84,387 Net loss attributable to noncontrolling interests — — (1,465 ) — (1,465 ) Net income attributable to WESCO International, Inc. $ 84,387 $ 74,876 $ 53,393 $ (126,804 ) $ 85,852 Other comprehensive income: Foreign currency translation adjustments 80,505 80,505 80,505 (161,010 ) 80,505 Post retirement benefit plan adjustment (16 ) (16 ) (16 ) 32 (16 ) Comprehensive income attributable to WESCO International, Inc. $ 164,876 $ 155,365 $ 133,882 $ (287,782 ) $ 166,341 Condensed Consolidating Statement of Cash Flows Six Months Ended June 30, 2017 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net cash provided by (used in) operating activities $ 9,117 $ 73,130 $ (15,478 ) $ — $ 66,769 Investing activities: Capital expenditures — (4,259 ) (5,536 ) — (9,795 ) Dividends received from subsidiaries — 33,818 — (33,818 ) — Other — (72,761 ) 12,322 63,906 3,467 Net cash (used in) provided by investing activities — (43,202 ) 6,786 30,088 (6,328 ) Financing activities: Borrowings 47,548 313,749 442,674 (72,636 ) 731,335 Repayments — (348,478 ) (420,847 ) 8,730 (760,595 ) Repurchases of common stock (56,665 ) — — — (56,665 ) Dividends paid by subsidiaries — — (33,818 ) 33,818 — Other — (613 ) — — (613 ) Net cash used in financing activities (9,117 ) (35,342 ) (11,991 ) (30,088 ) (86,538 ) Effect of exchange rate changes on cash and cash equivalents — — 3,765 — 3,765 Net change in cash and cash equivalents — (5,414 ) (16,918 ) — (22,332 ) Cash and cash equivalents at the beginning of period — 41,552 68,579 — 110,131 Cash and cash equivalents at the end of period $ — $ 36,138 $ 51,661 $ — $ 87,799 Condensed Consolidating Statement of Cash Flows Six Months Ended June 30, 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 $ (233 ) $ (236,891 ) $ 375,734 $ — $ 138,610 Investing activities: Capital expenditures — (5,507 ) (1,579 ) — (7,086 ) Acquisition payments, net of cash acquired — (50,946 ) — — (50,946 ) Dividends received from subsidiaries — 31,234 — (31,234 ) — Other — (23,477 ) 627 14,747 (8,103 ) Net cash used in investing activities — (48,696 ) (952 ) (16,487 ) (66,135 ) Financing activities: Borrowings 973 919,017 193,624 (23,477 ) 1,090,137 Repayments — (636,747 ) (537,712 ) 8,730 (1,165,729 ) Dividends paid by subsidiaries — — (31,234 ) 31,234 — Other (740 ) 152 — — (588 ) Net cash provided by (used in) financing activities 233 282,422 (375,322 ) 16,487 (76,180 ) Effect of exchange rate changes on cash and cash equivalents — — 3,716 — 3,716 Net change in cash and cash equivalents — (3,165 ) 3,176 — 11 Cash and cash equivalents at the beginning of period — 38,963 121,316 — 160,279 Cash and cash equivalents at the end of period $ — $ 35,798 $ 124,492 $ — $ 160,290

Subsequent Events SUBSEQUENT EV

Subsequent Events SUBSEQUENT EVENTS (Notes)	6 Months Ended
	Jun. 30, 2017
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.

GOODWILL (Notes)

GOODWILL (Notes)	6 Months Ended
	Jun. 30, 2017
Goodwill [Line Items]
Goodwill Disclosure [Text Block]	4. GOODWILL The following table sets forth the changes in the carrying value of goodwill: Six Months Ended June 30, June 30, (In thousands) Beginning balance January 1 $ 1,720,714 $ 1,681,662 Foreign currency exchange rate changes 20,826 40,062 Adjustments to goodwill for acquisitions (1) — 18,432 Ending balance June 30 $ 1,741,540 $ 1,740,156 (1) For the six months ended June 30, 2016 , adjustments relate to goodwill resulting from the preliminary allocation of the AED purchase price to the respective assets acquired and liabilities assumed, partially offset by a correction to goodwill for deferred income taxes related to prior acquisitions.

ACCOUNTING POLICIES (Policies)

ACCOUNTING POLICIES (Policies)	6 Months Ended
	Jun. 30, 2017
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 2016 Annual Report on Form 10-K as filed with the SEC on February 22, 2017. The Condensed Consolidated Balance Sheet at December 31, 2016 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 June 30, 2017 , the unaudited Condensed Consolidated Statements of Income and Comprehensive Income for the six months ended June 30, 2017 and 2016 , respectively, and the unaudited Condensed Consolidated Statements of Cash Flows for the six months ended June 30, 2017 and 2016 , 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.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company’s financial instruments consist of cash and cash equivalents, accounts receivable, accounts payable and other accrued liabilities, and outstanding indebtedness. The reported carrying amounts of WESCO’s financial 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.
New Accounting Pronouncements, Policy [Policy Text Block]	Recently Adopted Accounting Pronouncements In March 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (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. The Company adopted this ASU in the first quarter of 2017. The amendment related to the recognition of excess tax benefits and deficiencies was applied prospectively and, as disclosed in Note 9, lowered the Company's effective tax rate for the six months ended June 30, 2017 . The amendment related to the presentation of excess tax benefits on the statement of cash flows was also applied prospectively, and did not have a material impact on WESCO's cash flows. The other amendments, which were adopted by the Company according to the respective transition requirements, had no impact on the consolidated financial statements and notes thereto. In October 2016, the FASB issued ASU 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory. The purpose of ASU 2016-16 is to simplify the income tax accounting of an intra-entity transfer of an asset other than inventory and to record its effect when the transfer occurs. The Company early adopted this ASU on a modified retrospective basis in the first quarter of 2017. 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. During 2016, the FASB issued four ASUs that address implementation issues and correct or improve certain aspects of the new revenue recognition guidance, including ASU 2016-08, Principal versus Agent Considerations (Reporting Revenue Gross versus Net) , ASU 2016-10, Identifying Performance Obligations and Licensing , ASU 2016-12, Narrow-Scope Improvements and Practical Expedients and ASU 2016-20, Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers . These ASUs do not change the core principles in the revenue recognition standard outlined above. The Company has developed a multiphase plan and established a cross-functional team to evaluate and implement the new standard. Management is in the process of completing the diagnostic phase. In this phase, management is reviewing various customer contracts and comparing current accounting and disclosure policies to the requirements of the new standard. Management expects to adopt the new standard using the modified retrospective approach in the first quarter of 2018. The method of adoption is subject to change as management continues to evaluate the impact that this pronouncement may have 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 June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , which introduces new guidance for the accounting for credit losses on certain financial instruments. The amendments in ASU 2016-13 are effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years and early adoption is permitted. Management is currently evaluating the impact of this accounting standard on WESCO's consolidated financial statements and notes thereto. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (a consensus of the Emerging Issues Task Force) . This ASU provides guidance on eight specific cash flow issues where there is diversity in practice. The amendments in this ASU are effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted, including adoption in an interim period. Management is currently evaluating the impact of this accounting standard on WESCO's consolidated financial statements and notes thereto. In January 2017, the FASB issued ASU 2017-04, Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment, which eliminates Step 2 from the goodwill impairment test. Under the amendments in this update, an entity should perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. An entity should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. An entity should apply the amendments in this ASU on a prospective basis. This guidance is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Management has not yet evaluated the impact of this accounting standard on WESCO's consolidated financial statements and notes thereto. In March 2017, the FASB issued ASU 2017-07, Compensation—Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost . Presently, net benefit cost is reported as an employee cost within operating income (or capitalized into assets when appropriate). This amendment requires the bifurcation of net benefit cost. The service component will be presented with other employee compensation costs in operating income (or capitalized in assets). The other components will be reported separately outside of operations, and will not be eligible for capitalization. This guidance is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Early adoption is permitted. Management has not yet evaluated the impact of this accounting standard on WESCO's consolidated financial statements and notes thereto. In May 2017, the FASB issued ASU 2017-09, Compensation—Stock Compensation (Topic 718): Scope of Modification Accounting , which clarifies when to account for a change to the terms or conditions of a share-based payment award as a modification. Under the new guidance, modification accounting is required only if the fair value, the vesting conditions, or the classification of the award (as equity or liability) changes as a result of the change in terms or conditions. The guidance is effective prospectively for all companies for annual periods beginning on or after December 15, 2017. Early adoption is permitted. Management has not yet evaluated 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.

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	6 Months Ended
	Jun. 30, 2017
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 and six months ended June 30, 2017 and 2016 , 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 Six Months Ended June 30, June 30, June 30, June 30, Stock-settled stock appreciation rights granted — 4,744 443,731 708,254 Weighted-average fair value $ — $ 17.22 $ 20.65 $ 12.90 Restricted stock units granted — 137 98,680 143,305 Weighted-average fair value $ — $ 54.67 $ 71.65 $ 42.45 Performance-based awards granted — — 39,978 91,768 Weighted-average fair value $ — $ — $ 76.63 $ 47.00
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 six months ended June 30, 2017 : Awards Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (In years) Aggregate Intrinsic Value (In thousands) Outstanding at December 31, 2016 2,439,487 $ 52.62 Granted 443,731 71.65 Exercised (468,600 ) 42.48 Forfeited (87,445 ) 68.93 Outstanding at June 30, 2017 2,327,173 57.68 6.6 $ 17,651 Exercisable at June 30, 2017 1,398,502 $ 56.84 5.0 $ 11,783
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 six months ended June 30, 2017 : Awards Weighted- Average Fair Value Unvested at December 31, 2016 257,096 $ 57.47 Granted 98,680 71.65 Vested (43,169 ) 85.17 Forfeited (12,449 ) 53.91 Unvested at June 30, 2017 300,158 $ 58.29
Schedule of Nonvested Performance-based Units Activity [Table Text Block]	The following table sets forth a summary of performance-based awards for the six months ended June 30, 2017 : Awards Weighted- Average Fair Value Unvested at December 31, 2016 149,320 $ 60.36 Granted 39,978 76.63 Vested — — Forfeited (36,162 ) 79.64 Unvested at June 30, 2017 153,136 $ 60.05
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]	The fair value of stock-settled stock appreciation rights was estimated using the following weighted-average assumptions: Three Months Ended Six Months Ended June 30, June 30, June 30, June 30, Risk free interest rate — % 1.2 % 1.9 % 1.2 % Expected life (in years) 0 5 5 5 Expected volatility — % 32 % 29 % 32 %
Performance Shares [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]	The fair value of the performance shares granted during the six months ended June 30, 2017 and 2016 was estimated using the following weighted-average assumptions: Six Months Ended June 30, June 30, Grant date share price $ 71.65 $ 42.44 WESCO expected volatility 29 % 26 % Peer group median volatility 24 % 24 % Risk-free interest rate 1.5 % 0.9 % Correlation of peer company returns 114 % 122 %

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	6 Months Ended
	Jun. 30, 2017
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 Six Months Ended June 30, June 30, (In thousands, except per share data) 2017 2016 2017 2016 Net income attributable to WESCO International, Inc. $ 49,510 $ 49,798 $ 87,238 $ 85,852 Weighted-average common shares outstanding used in computing basic earnings per share 48,294 42,238 48,499 42,224 Common shares issuable upon exercise of dilutive equity awards 482 569 582 494 Common shares issuable from contingently convertible debentures (see below for basis of calculation) — 5,820 — 5,120 Weighted-average common shares outstanding and common share equivalents used in computing diluted earnings per share 48,776 48,627 49,081 47,838 Earnings per share attributable to WESCO International, Inc. Basic $ 1.03 $ 1.18 $ 1.80 $ 2.03 Diluted $ 1.02 $ 1.02 $ 1.78 $ 1.79

EMPLOYEE BENEFIT PLANS Schedule

EMPLOYEE BENEFIT PLANS Schedule of Net Benefit Costs (Tables)	6 Months Ended
	Jun. 30, 2017
Postemployment Benefits [Abstract]
Schedule of Net Benefit Costs [Table Text Block]	The following table reflects the components of net periodic benefit costs for the defined benefit plans: Three Months Ended Six Months Ended June 30, June 30, (In thousands of dollars) 2017 2016 2017 2016 Service cost $ 1,049 $ 990 $ 2,116 $ 1,913 Interest cost 945 993 1,907 1,918 Expected return on plan assets (1,343 ) (1,372 ) (2,711 ) (2,651 ) Recognized actuarial gain (48 ) (11 ) (97 ) (20 ) Net periodic benefit cost $ 603 $ 600 $ 1,215 $ 1,160

OTHER FINANCIAL INFORMATION (Ta

OTHER FINANCIAL INFORMATION (Tables)	6 Months Ended
	Jun. 30, 2017
Condensed Balance Sheet Statements, Captions [Line Items]
Condensed Balance Sheet [Table Text Block]	Condensed Consolidating Balance Sheet December 31, 2016 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Cash and cash equivalents $ — $ 41,552 $ 68,579 $ — $ 110,131 Trade accounts receivable, net — — 1,034,402 — 1,034,402 Inventories — 364,562 456,879 — 821,441 Prepaid expenses and other current assets 13,647 24,214 225,412 (56,790 ) 206,483 Total current assets 13,647 430,328 1,785,272 (56,790 ) 2,172,457 Intercompany receivables, net — — 2,056,783 (2,056,783 ) — Property, buildings and equipment, net — 51,824 105,783 — 157,607 Intangible assets, net — 3,417 389,945 — 393,362 Goodwill — 244,648 1,476,066 — 1,720,714 Investments in affiliates 3,584,857 4,018,661 — (7,603,518 ) — Other assets — 23,846 22,998 — 46,844 Total assets $ 3,598,504 $ 4,772,724 $ 5,836,847 $ (9,717,091 ) $ 4,490,984 Accounts payable $ — $ 381,795 $ 302,926 $ — $ 684,721 Short-term debt — — 20,920 — 20,920 Other current liabilities — 53,458 194,488 (56,790 ) 191,156 Total current liabilities — 435,253 518,334 (56,790 ) 896,797 Intercompany payables, net 1,572,486 484,297 — (2,056,783 ) — Long-term debt, net — 983,449 379,686 — 1,363,135 Other noncurrent liabilities 12,737 46,476 161,827 — 221,040 Total WESCO International, Inc. stockholders' equity 2,013,281 2,823,249 4,780,269 (7,603,518 ) 2,013,281 Noncontrolling interests — — (3,269 ) — (3,269 ) Total liabilities and stockholders’ equity $ 3,598,504 $ 4,772,724 $ 5,836,847 $ (9,717,091 ) $ 4,490,984 Condensed Consolidating Balance Sheet June 30, 2017 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Cash and cash equivalents $ — $ 36,138 $ 51,661 $ — $ 87,799 Trade accounts receivable, net — — 1,144,978 — 1,144,978 Inventories — 379,826 486,475 — 866,301 Prepaid expenses and other current assets 13,652 24,311 212,335 (43,831 ) 206,467 Total current assets 13,652 440,275 1,895,449 (43,831 ) 2,305,545 Intercompany receivables, net — — 2,118,924 (2,118,924 ) — Property, buildings and equipment, net — 49,797 105,406 — 155,203 Intangible assets, net — 3,094 377,332 — 380,426 Goodwill — 244,648 1,496,892 — 1,741,540 Investments in affiliates 3,717,402 4,139,039 — (7,856,441 ) — Other assets — 18,615 22,342 40,957 Total assets $ 3,731,054 $ 4,895,468 $ 6,016,345 $ (10,019,196 ) $ 4,623,671 Accounts payable $ — $ 413,605 $ 355,392 $ — $ 768,997 Short-term debt — — 23,972 — 23,972 Other current liabilities — 39,699 175,569 (43,831 ) 171,437 Total current liabilities — 453,304 554,933 (43,831 ) 964,406 Intercompany payables, net 1,620,034 498,890 — (2,118,924 ) — Long-term debt, net — 958,697 375,845 — 1,334,542 Other noncurrent liabilities 12,741 49,577 167,299 — 229,617 Total WESCO International, Inc. stockholders' equity 2,098,279 2,935,000 4,921,441 (7,856,441 ) 2,098,279 Noncontrolling interests — — (3,173 ) — (3,173 ) Total liabilities and stockholders’ equity $ 3,731,054 $ 4,895,468 $ 6,016,345 $ (10,019,196 ) $ 4,623,671

OTHER FINANCIAL INFORMATION Con

OTHER FINANCIAL INFORMATION Condensed Income Statement (Tables)	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Condensed Income Statements, Captions [Line Items]
Condensed Income Statement [Table Text Block]	Condensed Consolidating Statement of Income and Comprehensive Income Six Months Ended June 30, 2017 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 1,622,129 $ 2,120,315 $ (60,229 ) $ 3,682,215 Cost of goods sold (excluding depreciation and amortization) — 1,304,812 1,721,500 (60,229 ) 2,966,083 Selling, general and administrative expenses — 269,986 264,266 — 534,252 Depreciation and amortization — 9,336 22,350 — 31,686 Results of affiliates’ operations 87,334 75,181 — (162,515 ) — Interest expense (income), net — 49,525 (15,988 ) — 33,537 Income tax (benefit) expense — (2,898 ) 32,221 — 29,323 Net income 87,334 66,549 95,966 (162,515 ) 87,334 Net income attributable to noncontrolling interests — — 96 — 96 Net income attributable to WESCO International, Inc. $ 87,334 $ 66,549 $ 95,870 $ (162,515 ) $ 87,238 Other comprehensive income: Foreign currency translation adjustments 44,949 44,949 44,949 (89,898 ) 44,949 Post retirement benefit plan adjustment 252 252 252 (504 ) 252 Comprehensive income attributable to WESCO International, Inc. $ 132,535 $ 111,750 $ 141,071 $ (252,917 ) $ 132,439 Condensed Consolidating Statement of Income and Comprehensive Income Three Months Ended June 30, 2016 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 853,028 $ 1,087,050 $ (28,496 ) $ 1,911,582 Cost of goods sold (excluding depreciation and amortization) — 682,808 877,801 (28,496 ) 1,532,113 Selling, general and administrative expenses 11 142,942 131,570 — 274,523 Depreciation and amortization — 5,098 11,861 — 16,959 Results of affiliates’ operations 54,511 42,518 — (97,029 ) — Interest expense (income), net 6,333 20,845 (7,726 ) — 19,452 Income tax (benefit) expense (1,685 ) (1,108 ) 21,476 — 18,683 Net income 49,852 44,961 52,068 (97,029 ) 49,852 Net income attributable to noncontrolling interests — — 54 — 54 Net income attributable to WESCO International, Inc. $ 49,852 $ 44,961 $ 52,014 $ (97,029 ) $ 49,798 Other comprehensive loss: Foreign currency translation adjustments (1,765 ) (1,765 ) (1,765 ) 3,530 (1,765 ) Comprehensive income attributable to WESCO International, Inc. $ 48,087 $ 43,196 $ 50,249 $ (93,499 ) $ 48,033 Condensed Consolidating Statement of Income and Comprehensive Income Three Months Ended June 30, 2017 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 843,518 $ 1,100,661 $ (34,555 ) $ 1,909,624 Cost of goods sold (excluding depreciation and amortization) — 683,064 895,001 (34,555 ) 1,543,510 Selling, general and administrative expenses — 134,730 132,558 — 267,288 Depreciation and amortization — 4,583 11,138 — 15,721 Results of affiliates’ operations 49,535 40,753 — (90,288 ) — Interest expense (income), net — 28,518 (11,702 ) — 16,816 Income tax (benefit) expense — (1,862 ) 18,616 — 16,754 Net income 49,535 35,238 55,050 (90,288 ) 49,535 Net income attributable to noncontrolling interests — — 25 — 25 Net income attributable to WESCO International, Inc. $ 49,535 $ 35,238 $ 55,025 $ (90,288 ) $ 49,510 Other comprehensive income: Foreign currency translation adjustments 33,381 33,381 33,381 (66,762 ) 33,381 Comprehensive income attributable to WESCO International, Inc. $ 82,916 $ 68,619 $ 88,406 $ (157,050 ) $ 82,891	Condensed Consolidating Statement of Income and Comprehensive Income Six Months Ended June 30, 2016 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 1,653,518 $ 2,087,095 $ (53,070 ) $ 3,687,543 Cost of goods sold (excluding depreciation and amortization) — 1,322,481 1,683,495 (53,070 ) 2,952,906 Selling, general and administrative expenses (366 ) 223,149 321,026 — 543,809 Depreciation and amortization — 10,203 23,129 — 33,332 Results of affiliates’ operations 92,970 33,834 — (126,804 ) — Interest expense (income), net 12,651 39,704 (14,074 ) — 38,281 Income tax (benefit) expense (3,702 ) 16,939 21,591 — 34,828 Net income 84,387 74,876 51,928 (126,804 ) 84,387 Net loss attributable to noncontrolling interests — — (1,465 ) — (1,465 ) Net income attributable to WESCO International, Inc. $ 84,387 $ 74,876 $ 53,393 $ (126,804 ) $ 85,852 Other comprehensive income: Foreign currency translation adjustments 80,505 80,505 80,505 (161,010 ) 80,505 Post retirement benefit plan adjustment (16 ) (16 ) (16 ) 32 (16 ) Comprehensive income attributable to WESCO International, Inc. $ 164,876 $ 155,365 $ 133,882 $ (287,782 ) $ 166,341

OTHER FINANCIAL INFORMATION C23

OTHER FINANCIAL INFORMATION Condensed Cash Flow Statement (Tables)	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Condensed Cash Flow Statements, Captions [Line Items]
Condensed Cash Flow Statement [Table Text Block]	Condensed Consolidating Statement of Cash Flows Six Months Ended June 30, 2017 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net cash provided by (used in) operating activities $ 9,117 $ 73,130 $ (15,478 ) $ — $ 66,769 Investing activities: Capital expenditures — (4,259 ) (5,536 ) — (9,795 ) Dividends received from subsidiaries — 33,818 — (33,818 ) — Other — (72,761 ) 12,322 63,906 3,467 Net cash (used in) provided by investing activities — (43,202 ) 6,786 30,088 (6,328 ) Financing activities: Borrowings 47,548 313,749 442,674 (72,636 ) 731,335 Repayments — (348,478 ) (420,847 ) 8,730 (760,595 ) Repurchases of common stock (56,665 ) — — — (56,665 ) Dividends paid by subsidiaries — — (33,818 ) 33,818 — Other — (613 ) — — (613 ) Net cash used in financing activities (9,117 ) (35,342 ) (11,991 ) (30,088 ) (86,538 ) Effect of exchange rate changes on cash and cash equivalents — — 3,765 — 3,765 Net change in cash and cash equivalents — (5,414 ) (16,918 ) — (22,332 ) Cash and cash equivalents at the beginning of period — 41,552 68,579 — 110,131 Cash and cash equivalents at the end of period $ — $ 36,138 $ 51,661 $ — $ 87,799	Condensed Consolidating Statement of Cash Flows Six Months Ended June 30, 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 $ (233 ) $ (236,891 ) $ 375,734 $ — $ 138,610 Investing activities: Capital expenditures — (5,507 ) (1,579 ) — (7,086 ) Acquisition payments, net of cash acquired — (50,946 ) — — (50,946 ) Dividends received from subsidiaries — 31,234 — (31,234 ) — Other — (23,477 ) 627 14,747 (8,103 ) Net cash used in investing activities — (48,696 ) (952 ) (16,487 ) (66,135 ) Financing activities: Borrowings 973 919,017 193,624 (23,477 ) 1,090,137 Repayments — (636,747 ) (537,712 ) 8,730 (1,165,729 ) Dividends paid by subsidiaries — — (31,234 ) 31,234 — Other (740 ) 152 — — (588 ) Net cash provided by (used in) financing activities 233 282,422 (375,322 ) 16,487 (76,180 ) Effect of exchange rate changes on cash and cash equivalents — — 3,716 — 3,716 Net change in cash and cash equivalents — (3,165 ) 3,176 — 11 Cash and cash equivalents at the beginning of period — 38,963 121,316 — 160,279 Cash and cash equivalents at the end of period $ — $ 35,798 $ 124,492 $ — $ 160,290

GOODWILL (Tables)

GOODWILL (Tables)	6 Months Ended
	Jun. 30, 2017
Goodwill [Line Items]
Schedule of Goodwill [Table Text Block]	Six Months Ended June 30, June 30, (In thousands) Beginning balance January 1 $ 1,720,714 $ 1,681,662 Foreign currency exchange rate changes 20,826 40,062 Adjustments to goodwill for acquisitions (1) — 18,432 Ending balance June 30 $ 1,741,540 $ 1,740,156

ORGANIZATION (Details)

ORGANIZATION (Details)	Jun. 30, 2017customerscountriesbranches
Restructuring Cost and Reserve [Line Items]
Active customers (in customers) | customers	75,000
Full service branches (in branches) | branches	500
Additional countries (in countries) | countries	14

ACQUISITIONS - ACQUISITIONS (De

ACQUISITIONS - ACQUISITIONS (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2017USD ($)branches	Jun. 30, 2016USD ($)
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	$ 0	$ 50,946
Number of Stores | branches	500
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
Business Acquisition, Revenue Reported by Acquired Entity for Last Annual Period	$ 85,000
Finite-lived Intangible Assets Acquired	21,800
Goodwill, Acquired During Period	$ 30,000
Number of Stores	5
Customer Relationships [Member] | Atlanta Electrical Distributors, LLC (AED) [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired	$ 15,800
Noncompete Agreements [Member] | Atlanta Electrical Distributors, LLC (AED) [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired	$ 100
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	5 years
Trademarks [Member] | Atlanta Electrical Distributors, LLC (AED) [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired	$ 6,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	13 years
Minimum [Member] | Customer Relationships [Member] | Atlanta Electrical Distributors, LLC (AED) [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	13 years
Maximum [Member] | Customer Relationships [Member] | Atlanta Electrical Distributors, LLC (AED) [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 ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
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)			$ 42.48
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			$ 71.65
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	$ 11,783		$ 11,783
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$ 57.68		$ 57.68		$ 52.62
Share-based Compensation Arrangement By Share-based Payment Award, Options and Stock Appreciation Rights, Outstanding [Roll Forward]
Beginning of Year (in shares)	1,398,502		1,398,502
Grants in Period (in shares)	0	4,744	443,731	708,254
Exercises in Period (in shares)			468,600
Forfeitures in Period (in shares)			87,445
Weighted Average Exercise Price, Forfeitures in Period (in dollars per share)			$ 68.93
Weighted Average Exercise Price, Exercisable (in dollars per share)	$ 56.84		$ 56.84
Weighted Average Remaining Contractual Term, Outstanding (in years)			6 years 7 months 12 days
Weighted Average Remaining Contractual Term, Exercisable (in years)			5 years 6 days
Aggregate Intrinsic Value, Outstanding	$ 17,651		$ 17,651
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number	2,327,173		2,327,173		2,439,487

SCHEDULE OF SHARE-BASED PAYMENT

SCHEDULE OF SHARE-BASED PAYMENT AWARD, VALUATION ASSUMPTIONS (Details) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate	0.00%	1.20%	1.90%	1.20%
Expected life (in years)	0 years	5 years	5 years	5 years
WESCO expected volatility	0.00%	32.00%	29.00%	32.00%
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	0	4,744	443,731	708,254
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 0	$ 17.22	$ 20.65	$ 12.90
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	0	137	98,680	143,305
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 0	$ 54.67	$ 71.65	$ 42.45
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	0	0	39,978	91,768
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 0	$ 0	$ 76.63	$ 47
Risk free interest rate			0.00%	0.00%
WESCO expected volatility			0.00%	0.00%

SUMMARY OF RESTRICTED STOCK UNI

SUMMARY OF RESTRICTED STOCK UNITS (Details) - Restricted Stock Units (RSUs) [Member] - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Unvested (in shares)	300,158		300,158		257,096
Granted (in shares)	0	137	98,680	143,305
Vested (in shares)			(43,169)
Forfeited (in shares)			(12,449)
Unvested, Weighted Average Fair Value (in dollars per share)	$ 58.29		$ 58.29		$ 57.47
Granted, Weighted Average Fair Value (in dollars per share)	$ 0	$ 54.67	71.65	$ 42.45
Vested in Period, Weighted Average Fair Value (in dollars per share)			85.17
Forfeited in Period, Weighted Average Fair Value (in dollars per share)			$ 53.91

SUMMARY OF PERFORMANCE-BASED AW

SUMMARY OF PERFORMANCE-BASED AWARDS (Details) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Unvested (in shares)	153,136		153,136		149,320
Granted (in shares)	0	0	39,978	91,768
Vested (in shares)			0
Forfeited (in shares)			(36,162)
Unvested, Weighted Average Fair Value (in dollars per share)	$ 60.05		$ 60.05		$ 60.36
Granted, Weighted Average Fair Value (in dollars per share)	$ 0	$ 0	76.63	$ 47
Vested in Period, Weighted Average Fair Value (in dollars per share)			0
Forfeited in Period, Weighted Average Fair Value (in dollars per share)			$ 79.64
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)	76,568		76,568

SCHEDULE OF SHARE-BASED PAYME31

SCHEDULE OF SHARE-BASED PAYMENT AWARD, PERFORMANCE-BASED AWARDS, VALUATION ASSUMPTIONS (Details) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
WESCO expected volatility	0.00%	32.00%	29.00%	32.00%
Risk free interest rate	0.00%	1.20%	1.90%	1.20%
Correlation			0.00%	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	$ 71.65	$ 42.44	$ 71.65	$ 42.44
WESCO expected volatility			0.00%	0.00%
Risk free interest rate			0.00%	0.00%

STOCK-BASED COMPENSATION (Detai

STOCK-BASED COMPENSATION (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended			12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2017	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 4.1	$ 3.4		$ 7.8	$ 7
Total unrecognized compensation cost	$ 26.4			$ 26.4
Share-based Compensation Award, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance-based awards outstanding (in shares)	76,568			76,568
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)	76,568			76,568
Scenario, Forecast [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ 7.5			$ 0.7	$ 6.7	$ 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		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Net income (loss) attributable to WESCO International, Inc.	$ 49,510	$ 49,798	$ 87,238	$ 85,852
Weighted average common shares outstanding used in computing basic earnings per share (in shares)	48,294	42,238	48,499	42,224
Common shares issuable upon exercise of dilutive stock options (in shares)	482	569	582	494
Common shares issuable from contingently convertible debentures (in shares)	0	5,820	0	5,120
Weighted average common shares outstanding and common share equivalents used in computing diluted earnings per share (in shares)	48,776	48,627	49,081	47,838
Earnings Per Share, Basic and Diluted [Abstract]
Basic (in dollars per share)	$ 1.03	$ 1.18	$ 1.80	$ 2.03
Diluted (in dollars per share)	$ 1.02	$ 1.02	$ 1.78	$ 1.79

EARNINGS PER SHARE (Details)

EARNINGS PER SHARE (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Earnings Per Share Dilution Limit (in shares)	0	5,820,000	0	5,120,000
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		$ 28.87
Dilutive Securities, Effect on Basic Earnings Per Share		$ 0.14		$ 0.22
Equity Award [Domain]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,300,000	1,500,000	1,200,000	2,100,000
Convertible Debt Securities [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Earnings Per Share Dilution Limit (in shares)			11,951,932

EARNINGS PER SHARE Accelerated

EARNINGS PER SHARE Accelerated Share Repurchase (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2015
Accelerated Share Repurchases [Line Items]
Payments for Repurchase of Common Stock		$ (56,665)	$ (740)
Stock Repurchase Program, Authorized Amount	$ 300,000	$ 300,000
Treasury Stock, Shares, Acquired	804,291
Stock Repurchase Program Expiration Date		Dec. 31, 2017
Treasury Stock, Common [Member]
Accelerated Share Repurchases [Line Items]
Payments for Repurchase of Common Stock	$ (50,000)			$ (150,000)
Treasury Stock, Common, Shares	2,468,576	2,468,576

EMPLOYEE BENEFIT PLANS (Details

EMPLOYEE BENEFIT PLANS (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Retirement Benefits [Abstract]
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 0.5		$ 1
Schedule of Employee Benefit Plans [Line Items]
Postemployment Benefits, Period Expense		$ 10.6	$ 18.1
Deferred Compensation Liability, Classified, Noncurrent		$ 22.9		$ 21.7
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 of Match		50.00%
Defined Contribution Plan Employer Matching Contribution Percent		6.00%

EMPLOYEE BENEFIT PLANS EMPLOYEE

EMPLOYEE BENEFIT PLANS EMPLOYEE BENEFIT PLANS Pension Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Retirement Benefits [Abstract]
Defined Benefit Plan, Plan Assets, Contributions by Employer		$ 500		$ 1,000
Service cost	$ 1,049	990	$ 2,116	1,913
Interest cost	945	993	1,907	1,918
Expected return on plan assets	(1,343)	(1,372)	(2,711)	(2,651)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(48)	(11)	(97)	(20)
Net periodic benefit cost	$ 603	$ 600	$ 1,215	$ 1,160

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Tax Contingency [Line Items]
Effective tax rate	25.30%	27.26052%	25.10%	29.21444%
Federal statutory rate			35.00%
Unrecognized Tax Benefits			$ 1.5
Unrecognized Tax Benefits	$ 4.7		4.7
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	6		6
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	0.3		0.3
Settlement with Taxing Authority [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 0.1		$ 0.1

OTHER FINANCIAL INFORMATION (De

OTHER FINANCIAL INFORMATION (Details) - Unsecured Debt [Member] $ in Millions	Jun. 30, 2017USD ($)
2021 Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 500
2024 Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 350

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
Condensed Financial Information [Line Items]
Cash and cash equivalents	$ 87,799	$ 110,131	$ 160,290	$ 160,279
Trade accounts receivable, net	1,144,978	1,034,402
Inventories, net	866,301	821,441
Prepaid Expense and Other Assets, Current	137,146	121,464
Total current assets	2,305,545	2,172,457
Property, buildings and equipment, net	155,203	157,607
Intangible assets, net	380,426	393,362
Goodwill and other intangibles, net	1,741,540	1,720,714	1,740,156	1,681,662
Other assets	40,957	46,844
Total assets	4,623,671	4,490,984
Accounts payable	768,997	684,721
Short-term debt	23,972	20,920
Total current liabilities	964,406	896,797
Long-term Debt, Excluding Current Maturities	1,334,542	1,363,135
Total stockholders' equity	2,098,279	2,013,281
Stockholders' Equity Attributable to Noncontrolling Interest	3,173	3,269
Total liabilities and stockholders' equity	4,623,671	4,490,984
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	13,652	13,647
Total current assets	13,652	13,647
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	3,717,402	3,584,857
Other assets	0	0
Total assets	3,731,054	3,598,504
Accounts payable	0	0
Short-term debt	0	0
Other Liabilities, Current	0	0
Total current liabilities	0	0
Intercompany payables, net	1,620,034	1,572,486
Long-term Debt, Excluding Current Maturities	0	0
Liabilities, Other than Long-term Debt, Noncurrent	12,741	12,737
Total stockholders' equity	2,098,279	2,013,281
Stockholders' Equity Attributable to Noncontrolling Interest	0	0
Total liabilities and stockholders' equity	3,731,054	3,598,504
Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Cash and cash equivalents	36,138	41,552	35,798	38,963
Trade accounts receivable, net	0	0
Inventories, net	379,826	364,562
Prepaid Expense and Other Assets, Current	24,311	24,214
Total current assets	440,275	430,328
Intercompany receivables, net	0	0
Property, buildings and equipment, net	49,797	51,824
Intangible assets, net	3,094	3,417
Goodwill and other intangibles, net	244,648	244,648
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	4,139,039	4,018,661
Other assets	18,615	23,846
Total assets	4,895,468	4,772,724
Accounts payable	413,605	381,795
Short-term debt	0	0
Other Liabilities, Current	39,699	53,458
Total current liabilities	453,304	435,253
Intercompany payables, net	498,890	484,297
Long-term Debt, Excluding Current Maturities	958,697	983,449
Liabilities, Other than Long-term Debt, Noncurrent	49,577	46,476
Total stockholders' equity	2,935,000	2,823,249
Stockholders' Equity Attributable to Noncontrolling Interest	0	0
Total liabilities and stockholders' equity	4,895,468	4,772,724
Non-Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Cash and cash equivalents	51,661	68,579	124,492	121,316
Trade accounts receivable, net	1,144,978	1,034,402
Inventories, net	486,475	456,879
Prepaid Expense and Other Assets, Current	212,335	225,412
Total current assets	1,895,449	1,785,272
Intercompany receivables, net	2,118,924	2,056,783
Property, buildings and equipment, net	105,406	105,783
Intangible assets, net	377,332	389,945
Goodwill and other intangibles, net	1,496,892	1,476,066
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0	0
Other assets	22,342	22,998
Total assets	6,016,345	5,836,847
Accounts payable	355,392	302,926
Short-term debt	23,972	20,920
Other Liabilities, Current	175,569	194,488
Total current liabilities	554,933	518,334
Intercompany payables, net	0	0
Long-term Debt, Excluding Current Maturities	375,845	379,686
Liabilities, Other than Long-term Debt, Noncurrent	167,299	161,827
Total stockholders' equity	4,921,441	4,780,269
Stockholders' Equity Attributable to Noncontrolling Interest	3,173	3,269
Total liabilities and stockholders' equity	6,016,345	5,836,847
Consolidated Entities [Member]
Condensed Financial Information [Line Items]
Cash and cash equivalents	87,799	110,131	160,290	160,279
Trade accounts receivable, net	1,144,978	1,034,402
Inventories, net	866,301	821,441
Prepaid Expense and Other Assets, Current	206,467	206,483
Total current assets	2,305,545	2,172,457
Intercompany receivables, net	0	0
Property, buildings and equipment, net	155,203	157,607
Intangible assets, net	380,426	393,362
Goodwill and other intangibles, net	1,741,540	1,720,714
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0	0
Other assets	40,957	46,844
Total assets	4,623,671	4,490,984
Accounts payable	768,997	684,721
Short-term debt	23,972	20,920
Other Liabilities, Current	171,437	191,156
Total current liabilities	964,406	896,797
Intercompany payables, net	0	0
Long-term Debt, Excluding Current Maturities	1,334,542	1,363,135
Liabilities, Other than Long-term Debt, Noncurrent	229,617	221,040
Total stockholders' equity	2,098,279	2,013,281
Stockholders' Equity Attributable to Noncontrolling Interest	3,173	3,269
Total liabilities and stockholders' equity	4,623,671	4,490,984
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	(43,831)	(56,790)
Total current assets	(43,831)	(56,790)
Intercompany receivables, net	(2,118,924)	(2,056,783)
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	(7,856,441)	(7,603,518)
Other assets		0
Total assets	(10,019,196)	(9,717,091)
Accounts payable	0	0
Short-term debt	0	0
Other Liabilities, Current	(43,831)	(56,790)
Total current liabilities	(43,831)	(56,790)
Intercompany payables, net	(2,118,924)	(2,056,783)
Long-term Debt, Excluding Current Maturities	0	0
Liabilities, Other than Long-term Debt, Noncurrent	0	0
Total stockholders' equity	(7,856,441)	(7,603,518)
Stockholders' Equity Attributable to Noncontrolling Interest	0	0
Total liabilities and stockholders' equity	$ (10,019,196)	$ (9,717,091)

CONDENSED CONSOLIDATED INCOME S

CONDENSED CONSOLIDATED INCOME STATEMENTS (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Condensed Financial Information [Line Items]
Net sales	$ 1,909,624	$ 1,911,582	$ 3,682,215	$ 3,687,543
Cost of goods sold	1,543,510	1,532,113	2,966,083	2,952,906
Selling, general and administrative expense	267,288	274,523	534,252	543,809
Depreciation and amortization	15,721	16,959	31,686	33,332
Provision for income taxes	16,754	18,683	29,323	34,828
Net income (loss)	49,535	49,852	87,334	84,387
Less: Net (loss) income attributable to noncontrolling interest	25	54	96	(1,465)
Net income (loss) attributable to WESCO International, Inc.	49,510	49,798	87,238	85,852
Comprehensive Income:
Foreign currency translation adjustment	33,381	(1,765)	44,949	80,505
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	0	0	252	(16)
Comprehensive income attributable to WESCO International, Inc.	82,891	48,033	132,439	166,341
Parent Company [Member]
Condensed Financial Information [Line Items]
Net sales	0	0	0	0
Cost of goods sold	0	0	0	0
Selling, general and administrative expense	0	11	0	(366)
Depreciation and amortization	0	0	0	0
Income (Loss) from Subsidiaries, before Tax	49,535	54,511	87,334	92,970
Interest Income (Expense), Net	0	(6,333)	0	(12,651)
Provision for income taxes	0	(1,685)	0	(3,702)
Net income (loss)	49,535	49,852	87,334	84,387
Less: Net (loss) income attributable to noncontrolling interest	0	0	0	0
Net income (loss) attributable to WESCO International, Inc.	49,535	49,852	87,334	84,387
Comprehensive Income:
Foreign currency translation adjustment	33,381	(1,765)	44,949	80,505
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax			(252)	16
Comprehensive income attributable to WESCO International, Inc.	82,916	48,087	132,535	164,876
Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Net sales	843,518	853,028	1,622,129	1,653,518
Cost of goods sold	683,064	682,808	1,304,812	1,322,481
Selling, general and administrative expense	134,730	142,942	269,986	223,149
Depreciation and amortization	4,583	5,098	9,336	10,203
Income (Loss) from Subsidiaries, before Tax	40,753	42,518	75,181	33,834
Interest Income (Expense), Net	(28,518)	(20,845)	(49,525)	(39,704)
Provision for income taxes	(1,862)	(1,108)	(2,898)	16,939
Net income (loss)	35,238	44,961	66,549	74,876
Less: Net (loss) income attributable to noncontrolling interest	0	0	0	0
Net income (loss) attributable to WESCO International, Inc.	35,238	44,961	66,549	74,876
Comprehensive Income:
Foreign currency translation adjustment	33,381	(1,765)	44,949	80,505
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax			(252)	16
Comprehensive income attributable to WESCO International, Inc.	68,619	43,196	111,750	155,365
Non-Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Net sales	1,100,661	1,087,050	2,120,315	2,087,095
Cost of goods sold	895,001	877,801	1,721,500	1,683,495
Selling, general and administrative expense	132,558	131,570	264,266	321,026
Depreciation and amortization	11,138	11,861	22,350	23,129
Income (Loss) from Subsidiaries, before Tax	0	0	0	0
Interest Income (Expense), Net	(11,702)	(7,726)	(15,988)	(14,074)
Provision for income taxes	18,616	21,476	32,221	21,591
Net income (loss)	55,050	52,068	95,966	51,928
Less: Net (loss) income attributable to noncontrolling interest	25	54	96	(1,465)
Net income (loss) attributable to WESCO International, Inc.	55,025	52,014	95,870	53,393
Comprehensive Income:
Foreign currency translation adjustment	33,381	(1,765)	44,949	80,505
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax			(252)	16
Comprehensive income attributable to WESCO International, Inc.	88,406	50,249	141,071	133,882
Consolidated Entities [Member]
Condensed Financial Information [Line Items]
Net sales	1,909,624	1,911,582	3,682,215	3,687,543
Cost of goods sold	1,543,510	1,532,113	2,966,083	2,952,906
Selling, general and administrative expense	267,288	274,523	534,252	543,809
Depreciation and amortization	15,721	16,959	31,686	33,332
Income (Loss) from Subsidiaries, before Tax	0	0	0	0
Interest Income (Expense), Net	(16,816)	(19,452)	(33,537)	(38,281)
Provision for income taxes	16,754	18,683	29,323	34,828
Net income (loss)	49,535	49,852	87,334	84,387
Less: Net (loss) income attributable to noncontrolling interest	25	54	96	(1,465)
Net income (loss) attributable to WESCO International, Inc.	49,510	49,798	87,238	85,852
Comprehensive Income:
Foreign currency translation adjustment	33,381	(1,765)	44,949	80,505
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax			(252)	16
Comprehensive income attributable to WESCO International, Inc.	82,891	48,033	132,439	166,341
Consolidation, Eliminations [Member]
Condensed Financial Information [Line Items]
Net sales	(34,555)	(28,496)	(60,229)	(53,070)
Cost of goods sold	(34,555)	(28,496)	(60,229)	(53,070)
Selling, general and administrative expense	0	0	0	0
Depreciation and amortization	0	0	0	0
Income (Loss) from Subsidiaries, before Tax	(90,288)	(97,029)	(162,515)	(126,804)
Interest Income (Expense), Net	0	0	0	0
Provision for income taxes	0	0	0	0
Net income (loss)	(90,288)	(97,029)	(162,515)	(126,804)
Less: Net (loss) income attributable to noncontrolling interest	0	0	0	0
Net income (loss) attributable to WESCO International, Inc.	(90,288)	(97,029)	(162,515)	(126,804)
Comprehensive Income:
Foreign currency translation adjustment	(66,762)	3,530	(89,898)	(161,010)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax			504	(32)
Comprehensive income attributable to WESCO International, Inc.	$ (157,050)	$ (93,499)	$ (252,917)	$ (287,782)

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENT OF CASH FLOWS (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	$ 3,467	$ (8,103)
Net cash (used) provided by operating activities	66,769	138,610
Investing Activities:
Capital expenditures	(9,795)	(7,086)
Acquisition payments	0	(50,946)
Net cash used in investing activities	(6,328)	(66,135)
Financing Activities:
Proceeds from (Repayments of) Bank Overdrafts	155	6,474
Payments for Repurchase of Common Stock	(56,665)	(740)
Proceeds from (Payments for) Other Financing Activities	(768)	(6,322)
Net cash used in financing activities	(86,538)	(76,180)
Effect of exchange rate changes on cash and cash equivalents	3,765	3,716
Net change in cash and cash equivalents	(22,332)	11
Cash and cash equivalents at the beginning of period	110,131	160,279
Cash and cash equivalents at the end of period	87,799	160,290
Parent Company [Member]
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	0	0
Net cash (used) provided by operating activities	9,117	(233)
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	47,548	973
Repayments	0	0
Cash Dividends Paid to Parent Company	0	0
Payments for Repurchase of Common Stock	56,665
Proceeds from (Payments for) Other Financing Activities	0	(740)
Net cash used in financing activities	(9,117)	233
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
Cash and cash equivalents at the end of period	0	0
Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	(72,761)	(23,477)
Net cash (used) provided by operating activities	73,130	(236,891)
Investing Activities:
Capital expenditures	(4,259)	(5,507)
Acquisition payments		(50,946)
Proceeds from Dividends Received	33,818	31,234
Net cash used in investing activities	(43,202)	(48,696)
Financing Activities:
Borrowings	313,749	919,017
Repayments	(348,478)	(636,747)
Cash Dividends Paid to Parent Company	0	0
Payments for Repurchase of Private Placement	0
Proceeds from (Payments for) Other Financing Activities	(613)	152
Net cash used in financing activities	(35,342)	282,422
Effect of exchange rate changes on cash and cash equivalents	0	0
Net change in cash and cash equivalents	(5,414)	(3,165)
Cash and cash equivalents at the beginning of period	41,552	38,963
Cash and cash equivalents at the end of period	36,138	35,798
Non-Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	12,322	627
Net cash (used) provided by operating activities	(15,478)	375,734
Investing Activities:
Capital expenditures	(5,536)	(1,579)
Acquisition payments		0
Proceeds from Dividends Received	0	0
Net cash used in investing activities	6,786	(952)
Financing Activities:
Borrowings	442,674	193,624
Repayments	(420,847)	(537,712)
Cash Dividends Paid to Parent Company	(33,818)	(31,234)
Payments for Repurchase of Common Stock	0
Proceeds from (Payments for) Other Financing Activities	0	0
Net cash used in financing activities	(11,991)	(375,322)
Effect of exchange rate changes on cash and cash equivalents	3,765	3,716
Net change in cash and cash equivalents	(16,918)	3,176
Cash and cash equivalents at the beginning of period	68,579	121,316
Cash and cash equivalents at the end of period	51,661	124,492
Consolidated Entities [Member]
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	3,467	(8,103)
Net cash (used) provided by operating activities	66,769	138,610
Investing Activities:
Capital expenditures	(9,795)	(7,086)
Acquisition payments		(50,946)
Proceeds from Dividends Received	0	0
Net cash used in investing activities	(6,328)	(66,135)
Financing Activities:
Borrowings	731,335	1,090,137
Repayments	(760,595)	(1,165,729)
Cash Dividends Paid to Parent Company	0	0
Payments for Repurchase of Common Stock	56,665
Proceeds from (Payments for) Other Financing Activities	(613)	(588)
Net cash used in financing activities	(86,538)	(76,180)
Effect of exchange rate changes on cash and cash equivalents	3,765	3,716
Net change in cash and cash equivalents	(22,332)	11
Cash and cash equivalents at the beginning of period	110,131	160,279
Cash and cash equivalents at the end of period	87,799	160,290
Consolidation, Eliminations [Member]
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	63,906	14,747
Net cash (used) provided by operating activities	0	0
Investing Activities:
Capital expenditures	0	0
Acquisition payments		0
Proceeds from Dividends Received	(33,818)	(31,234)
Net cash used in investing activities	30,088	(16,487)
Financing Activities:
Borrowings	(72,636)	(23,477)
Repayments	(8,730)	(8,730)
Cash Dividends Paid to Parent Company	(33,818)	(31,234)
Payments for Repurchase of Common Stock	0
Proceeds from (Payments for) Other Financing Activities	0	0
Net cash used in financing activities	(30,088)	16,487
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
Cash and cash equivalents at the end of period	$ 0	$ 0

GOODWILL (Details)

GOODWILL (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Goodwill	$ 1,741,540	$ 1,740,156	$ 1,720,714	$ 1,681,662
Goodwill, Foreign Currency Translation Gain (Loss)	20,826	40,062
Goodwill, Purchase Accounting Adjustments	$ 0	$ 18,432