WESCO International (WCC) 10-Q 3 Aug 18 2018 Q2 Quarterly report Financial data

DOCUMENT AND ENTITY INFORMATION

DOCUMENT AND ENTITY INFORMATION Document - shares	6 Months Ended
	Jun. 30, 2018	Aug. 02, 2018
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, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Common Stock, Shares Outstanding		47,099,411

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Dec. 31, 2017USD ($)
Depreciation, Depletion and Amortization, Nonproduction	$ 15,823	$ 31,703
Other Accrued Liabilities, Current	88,366	88,366	$ 95,820
Current Assets:
Cash and cash equivalents	110,940	110,940	117,953
Allowance for Doubtful Accounts Receivable, Current	22,763	22,763	21,313
Trade accounts receivable, net of allowance for doubtful accounts of $23,069 and $19,309 in 2014 and 2013, respectively	1,257,330	1,257,330	1,170,080
Accounts and Other Receivables, Net, Current	62,361	62,361	101,229
Inventories, net	935,231	935,231	956,148
Prepaid expenses and other current assets	81,078	81,078	63,439
Total current assets	2,446,940	2,446,940	2,408,849
Property, buildings and equipment, net of accumulated depreciation of $229,041 and $213,758 in 2014 and 2013, respectively	157,492	157,492	156,445
Intangible assets, net	340,579	340,579	367,104
Goodwill	1,744,694	1,744,694	1,771,877
Other assets	25,281	25,281	31,193
Total assets	4,714,986	4,714,986	4,735,468
Current Liabilities:
Accounts payable	818,179	818,179	799,520
Accrued payroll and benefit costs	54,353	54,353	72,686
Short-term debt	35,527	35,527	34,075
Current portion of long-term debt	1,188	1,188	1,224
Total current liabilities	1,025,909	1,025,909	1,040,969
Long-term Debt, Excluding Current Maturities	1,261,705	1,261,705	1,313,261
Other noncurrent liabilities	121,119	121,119	128,237
Deferred Tax Liabilities, Net, Noncurrent	140,498	140,498	136,858
Total liabilities	2,549,231	2,549,231	2,619,325
Commitments and Contingencies
Bank Overdrafts	28,296	28,296	37,644
Stockholders' Equity:
Preferred stock, $.01 par value; 20,000,000 shares authorized, no shares issued or outstanding	0	0	0
Additional capital	1,005,897	1,005,897	999,156
Retained earnings	2,182,484	2,182,484	2,079,697
Treasury stock, at cost; 18,247,467 and 18,179,275 shares in 2014 and 2013, respectively	(647,843)	(647,843)	(647,158)
Accumulated other comprehensive income	(370,105)	(370,105)	(312,590)
Total WESCO International stockholders' equity	2,165,755	2,165,755	2,116,143
Noncontrolling interest	(5,312)	(5,312)	(3,596)
Total stockholders' equity	2,171,067	2,171,067	2,119,739
Total liabilities and stockholders' equity	4,714,986	4,714,986	4,735,468
Common Stock [Member]
Stockholders' Equity:
Common stock	591	591	591
Common Class B [Member]
Stockholders' Equity:
Common stock	$ 43	$ 43	$ 43

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parentheticals) - USD ($)	Jun. 30, 2018	Dec. 31, 2017
Allowance for doubtful accounts	$ 22,763,000	$ 21,313,000
Accumulated depreciation	285,632,000	278,455,000
Finite-Lived Intangible Assets, Accumulated Amortization	237,716	223,554
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ 11,441,000	$ 14,224,000
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)	16,384,969	16,375,653
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)	59,144,569	59,045,762
Common stock, shares outstanding (in shares)	47,099,031	47,009,540
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, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenues	$ 2,103,994	$ 1,909,624	$ 4,097,909	$ 3,682,215
Cost of goods sold	1,704,100	1,543,510	3,318,066	2,966,083
Selling, general and administrative expense	292,888	267,735	583,717	535,153
Depreciation and amortization	15,823	15,721	31,703	31,686
Income from operations	91,183	82,658	164,423	149,293
Nonoperating Income (Expense)	17,741	16,369	37,524	32,636
Income before income taxes	73,442	66,289	126,899	116,657
Provision for income taxes	15,769	16,754	26,255	29,323
Net income	57,673	49,535	100,644	87,334
Net (loss) income attributable to noncontrolling interest	(267)	25	(1,717)	96
Net income attributable to WESCO International, Inc.	57,940	49,510	102,361	87,238
Comprehensive Income:
Foreign currency translation adjustment	(28,715)	33,381	(57,515)	44,949
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	0	0	0	252
Comprehensive income attributable to WESCO International, Inc.	$ 29,225	$ 82,891	$ 44,846	$ 132,439
Earnings per share attributable to WESCO International, Inc.
Basic (in dollars per share)	$ 1.23	$ 1.03	$ 2.18	$ 1.80
Diluted (in dollars per share)	$ 1.22	$ 1.02	$ 2.15	$ 1.78
Shipping and Handling [Member]
Cost of goods sold	$ 18,600	$ 14,400	$ 36,800	$ 27,800

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Statement of Cash Flows [Abstract]
Interest Paid, Including Capitalized Interest, Operating and Investing Activities	$ 32,380	$ 30,776
Operating Activities:
Net income	100,644	87,334
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	31,703	31,686
Deferred income taxes	6,100	6,404
Other operating activities, net	11,027	8,306
Changes in assets and liabilities
Increase (Decrease) in Accounts Receivable	102,567	95,978
Increase (Decrease) in Accounts and Other Receivables	(38,430)	(16,425)
Inventories, net	11,407	(36,877)
Prepaid expenses and other current assets	(12,866)	(6,360)
Accounts payable	26,073	76,836
Accrued payroll and benefit costs	(16,588)	(10,786)
Other current and noncurrent liabilities	(6,542)	(10,221)
Net cash provided by operating activities	86,821	66,769
Investing Activities:
Capital expenditures	(16,384)	(9,795)
Other investing activities	(8,684)	3,467
Net cash used in investing activities	(25,068)	(6,328)
Financing Activities:
Proceeds from issuance of short-term debt	87,861	69,257
Repayments of short-term debt	(85,761)	(68,517)
Proceeds from issuance of long-term debt	794,888	662,078
Repayments of Long-term Debt	(848,888)	(692,078)
Other financing activities, net	(550)	(768)
Net cash used in financing activities	(63,749)	(86,538)
Payments for Repurchase of Common Stock	(1,891)	(56,665)
Proceeds from (Repayments of) Bank Overdrafts	(9,408)	155
Effect of exchange rate on cash and cash equivalents	(5,017)	3,765
Net change in cash and cash equivalents	(7,013)	(22,332)
Cash and cash equivalents at the beginning of period	117,953	110,131
Cash and cash equivalents at the end of period	110,940	87,799
Income Taxes Paid	$ 33,792	$ 30,664

ORGANIZATION

ORGANIZATION	6 Months Ended
	Jun. 30, 2018
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 70,000 active customers globally through approximately 500 branches and 10 distribution centers located primarily in the United States and Canada, with operations in 16 additional countries.

ACCOUNTING POLICIES

ACCOUNTING POLICIES	6 Months Ended
	Jun. 30, 2018
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 2017 Annual Report on Form 10-K as filed with the SEC on February 22, 2018. The Condensed Consolidated Balance Sheet at December 31, 2017 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, 2018 , the unaudited Condensed Consolidated Statements of Income and Comprehensive Income for the six months ended June 30, 2018 and 2017 , respectively, and the unaudited Condensed Consolidated Statements of Cash Flows for the six months ended June 30, 2018 and 2017 , 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. Reclassifications Effective January 1, 2018, WESCO adopted Accounting Standards Update (ASU) 2017-07, Compensation—Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost . The adoption of this ASU, as described below and in Note 8, resulted in the reclassification of amounts reported in the unaudited Condensed Consolidated Statements of Income and Comprehensive Income for the three and six months ended June 30, 2017 . Recently Adopted Accounting Pronouncements Effective January 1, 2018, WESCO adopted ASU 2014-09, Revenue from Contracts with Customers , and all the related amendments (“Topic 606”) using the modified retrospective approach to all open contracts. There was no impact to WESCO’s previously reported consolidated financial statements and WESCO does not expect the adoption of Topic 606 to have a material impact on its revenue and results of operations on an ongoing basis. WESCO’s significant accounting policies are disclosed in Note 2 of the Notes to Consolidated Financial Statements in the Annual Report on Form 10-K for the year ended December 31, 2017. Changes to the Company’s significant accounting policies as a result of adopting Topic 606 are described in Note 3 below. In August 2016, the Financial Accounting Standards Board (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 Company adopted this ASU in the first quarter of 2018. The adoption of this guidance did not have an impact on the unaudited condensed consolidated financial information presented herein. 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 . This ASU requires that an employer disaggregate the service cost from the other components of net benefit cost. The Company adopted this guidance on a retrospective basis in the first quarter of 2018. See Note 8 for a description of the impact of this accounting standard on the unaudited Condensed Consolidated Statements of Income and Comprehensive Income presented herein. The adoption of this guidance did not have an impact on the Company's unaudited Condensed Consolidated Balance Sheets and the unaudited Condensed Consolidated Statements of Cash Flows presented herein. In May 2017, the FASB issued ASU 2017-09, Compensation—Stock Compensation (Topic 718): Scope of Modification Accounting. This ASU 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 Company adopted this ASU in the first quarter of 2018. The adoption of this guidance did not have an impact on the unaudited condensed consolidated financial information presented herein. Recently Issued Accounting Pronouncements 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 in the balance sheet and disclosing key information about leasing arrangements. This ASU 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 has established a cross-functional team to evaluate and implement the new standard. The team is currently in the process of gathering lease data and selecting a third-party software solution to assist with accounting for leases under the new standard. Upon adoption, right-of-use assets and lease liabilities will be recorded in the Consolidated Balance Sheets. 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 this ASU are effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted. Management does not expect the adoption of this accounting standard to have a material impact on its 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 of the goodwill impairment test. Under the amendments in this ASU, 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 expects to adopt this ASU in the fourth quarter of 2018 when the Company performs its annual impairment testing. The Company does not expect the adoption of this accounting standard to have a material impact on its consolidated financial statements and notes thereto. Other pronouncements issued by the FASB or other authoritative accounting standards groups with future effective dates are either not applicable or are not expected to be significant to WESCO’s financial position, results of operations or cash flows.

ACQUISITIONS

ACQUISITIONS	6 Months Ended
	Jun. 30, 2018
Business Combinations [Abstract]
ACQUISITIONS	3. REVENUE WESCO’s revenue arrangements generally consist of single performance obligations to transfer a promised good or service, or a combination of goods and services. Revenue is recognized when control has transferred to the customer, which is generally when the product has shipped from a WESCO facility or directly from a supplier. For products that ship directly from suppliers to customers, WESCO acts as the principal in the transaction and recognizes revenue on a gross basis. Revenue for integrated supply services is recognized over time based on hours incurred. This method reflects the transfer of control as the customer benefits from these services as they are being performed. WESCO generally satisfies its performance obligations within a year or less. WESCO generally does not have significant financing terms associated with its contracts; payments are normally received within 60 days. There are no significant costs associated with obtaining customer contracts. WESCO generally passes through the warranties offered by the applicable manufacturer or supplier to its customers. Sales taxes (and value added taxes in foreign jurisdictions) collected from customers and remitted to governmental authorities are excluded from net sales. The following tables disaggregate WESCO’s revenue by end market and geography: Three Months Ended Six Months Ended June 30 June 30 (In thousands) 2018 2017 2018 2017 Industrial $ 760,741 $ 711,305 $ 1,519,723 $ 1,389,601 Construction 683,752 623,763 1,321,551 1,195,392 Utility 336,961 282,400 652,506 548,660 Commercial, Institutional and Government ("CIG") 322,540 292,156 604,129 548,562 Total by end market $ 2,103,994 $ 1,909,624 $ 4,097,909 $ 3,682,215 Three Months Ended Six Months Ended June 30 June 30 (In thousands) 2018 2017 2018 2017 United States $ 1,563,392 $ 1,451,401 $ 3,046,140 $ 2,794,601 Other (1) 540,602 458,223 1,051,769 887,614 Total by geography $ 2,103,994 $ 1,909,624 $ 4,097,909 $ 3,682,215 (1) Other primarily includes net sales to customers in Canada. WESCO distributes products and provides services to customers globally within the following end markets: (1) industrial, (2) construction, (3) utility, and (4) CIG. Revenue is measured as the amount of consideration WESCO expects to receive in exchange for transferring goods or providing services. In accordance with certain contractual arrangements, WESCO receives payment from its customers in advance and recognizes such payment as deferred revenue. Revenue for advance payment is recognized when the performance obligation has been satisfied and control has transferred to the customer, which is generally upon shipment. Deferred revenue is usually recognized within a year or less from the date of the customer’s advance payment. At June 30, 2018 and December 31, 2017 , $11.6 million and $15.5 million , respectively, of deferred revenue was recorded as a component of other current liabilities in the Condensed Consolidated Balance Sheets. WESCO’s revenues are adjusted for variable consideration, which includes customer volume rebates, returns, and discounts. WESCO measures variable consideration by estimating expected outcomes using analysis and inputs based upon anticipated performance, historical data, as well as current and forecasted information. Measurement and recognition of variable consideration is reviewed by management on a monthly basis and revenue is adjusted accordingly. Variable consideration reduced revenue for the three months ended June 30, 2018 and 2017 by approximately $25.0 million and $21.7 million , respectively, and by approximately $49.4 million and $42.3 million for the six months ended June 30, 2018 and 2017 , respectively. Shipping and handling costs are recognized in net sales when they are billed to the customer. These costs are recognized as a component of selling, general and administrative expenses when WESCO does not bill the customer. WESCO has elected to recognize shipping and handling costs as a fulfillment cost. Shipping and handling costs recorded as a component of selling, general and administrative expenses totaled $18.6 million and $14.4 million for the three months ended June 30, 2018 and 2017 , respectively, and $36.8 million and $27.8 million for the six months ended June 30, 2018 and 2017 , respectively.

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	6 Months Ended
	Jun. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
STOCK-BASED COMPENSATION	. STOCK-BASED COMPENSATION WESCO’s stock-based employee compensation plans are comprised of stock-settled stock appreciation rights, restricted stock units and performance-based awards. Compensation cost for all stock-based awards is measured at fair value on the date of grant and compensation cost is recognized, net of estimated forfeitures, over the service period for awards expected to vest. The fair value of stock-settled stock appreciation rights and performance-based awards with market conditions is determined using the Black-Scholes and Monte Carlo simulation models, respectively. The fair value of restricted stock units and performance-based awards with performance conditions is determined by the grant-date closing price of WESCO’s common stock. The forfeiture assumption is based on WESCO’s historical employee behavior that is reviewed on an annual basis. No dividends are assumed. Effective January 1, 2018, performance-based awards are based on two equally-weighted performance measures, which include the three-year average growth rate of the Company’s fully diluted earnings per share and the three-year cumulative return on net assets. From 2015 to 2017, the two equally-weighted performance-based award metrics were the three-year average growth rate of WESCO's net income and WESCO's total stockholder return in relation to the total stockholder return of a select group of peer companies over a three-year period. During the three and six months ended June 30, 2018 and 2017 , 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 8,402 — 499,631 443,731 Weighted-average fair value $ 17.85 $ — $ 18.39 $ 20.65 Restricted stock units granted 2,502 — 116,771 98,680 Weighted-average fair value $ 59.95 $ — $ 62.75 $ 71.65 Performance-based awards granted — — 44,144 39,978 Weighted-average fair value $ — $ — $ 62.80 $ 76.63 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 2.8 % n/a 2.5 % 1.9 % Expected life (in years) 5 n/a 5 5 Expected volatility 28 % n/a 28 % 29 % The risk-free interest rate is based on the U.S. Treasury Daily Yield Curve 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, 2018 : Awards Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (In years) Aggregate Intrinsic Value (In thousands) Outstanding at December 31, 2017 2,238,607 $ 57.75 Granted 499,631 62.76 Exercised (158,279 ) 39.63 Forfeited (135,511 ) 68.78 Outstanding at June 30, 2018 2,444,448 59.33 6.6 $ 13,624 Exercisable at June 30, 2018 1,523,126 $ 58.09 5.2 $ 11,130 The following table sets forth a summary of time-based restricted stock units and related information for the six months ended June 30, 2018 : Awards Weighted- Average Fair Value Unvested at December 31, 2017 290,054 $ 58.11 Granted 116,771 62.75 Vested (57,175 ) 69.44 Forfeited (10,710 ) 56.45 Unvested at June 30, 2018 338,940 $ 57.85 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, 2018 : Awards Weighted- Average Fair Value Unvested at December 31, 2017 148,508 $ 60.23 Granted 44,144 62.80 Vested — — Forfeited (52,342 ) 65.31 Unvested at June 30, 2018 140,310 $ 59.33 The fair value of the performance shares granted during the six months ended June 30, 2018 and 2017 was estimated using the following weighted-average assumptions: Six Months Ended June 30, June 30, Grant date share price $ 62.80 $ 71.65 WESCO expected volatility n/a 29 % Peer group median volatility n/a 24 % Risk-free interest rate n/a 1.5 % Correlation of peer company returns n/a 114 % The unvested performance-based awards in the table above include 48,805 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 91,505 shares of performance-based awards in the table above is dependent upon the achievement of certain performance targets, including 48,805 that are dependent upon the three-year average growth rate of WESCO's net income, 21,350 that are dependent upon the three-year average growth rate of the Company's fully diluted earnings per share, and 21,350 that are based upon the three-year cumulative return on net assets. 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 $4.4 million and $4.1 million of non-cash stock-based compensation expense, which is included in selling, general and administrative expenses, for the three months ended June 30, 2018 and 2017 , respectively. WESCO recognized $8.0 million and $7.8 million of non-cash stock-based compensation expense, which is included in selling, general and administrative expenses, for the six months ended June 30, 2018 and 2017 , respectively. As of June 30, 2018 , there was $27.0 million of total unrecognized compensation cost related to non-vested stock-based compensation arrangements for all awards previously made, of which approximately $8.3 million is expected to be recognized over the remainder of 2018 , $11.7 million in 2019 , $6.3 million in 2020 and $0.7 million in 2021 .

EARNINGS PER SHARE

EARNINGS PER SHARE	6 Months Ended
	Jun. 30, 2018
Earnings Per Share [Abstract]
EARNINGS PER SHARE	7. 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. 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) 2018 2017 2018 2017 Net income attributable to WESCO International $ 57,940 $ 49,510 $ 102,361 $ 87,238 Weighted-average common shares outstanding used in computing basic earnings per share 47,085 48,294 47,062 48,499 Common shares issuable upon exercise of dilutive equity awards 465 482 516 582 Weighted-average common shares outstanding and common share equivalents used in computing diluted earnings per share 47,550 48,776 47,578 49,081 Earnings per share attributable to WESCO International Basic $ 1.23 $ 1.03 $ 2.18 $ 1.80 Diluted $ 1.22 $ 1.02 $ 2.15 $ 1.78 For the three and six months ended June 30, 2018 the computation of diluted earnings per share attributable to WESCO International excluded stock-based awards of approximately 1.5 million . For the three and six months ended June 30, 2017 , the computation of diluted earnings per share attributable to WESCO International excluded stock-based awards of approximately 1.3 million and 1.2 million , respectively. These amounts were excluded because their effect would have been antidilutive. 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 (the "2014 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 pursuant to its 2014 Repurchase Authorization. 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 for the three and six months ended June 30, 2017 , 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, 2018
Retirement Benefits [Abstract]
EMPLOYEE BENEFIT PLANS	8. 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 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, 2018 and 2017 , WESCO incurred charges of $21.9 million and $10.6 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, 2018 and December 31, 2017 , the Company's obligation under the deferred compensation plan was $24.0 million and $24.3 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. The Company sponsors a contributory defined benefit plan covering substantially all Canadian employees of EECOL and a Supplemental Executive Retirement Plan (the "SERP") for certain executives of EECOL. During the three and six months ended June 30, 2018 , the Company contributed $0.1 million and $0.2 million , respectively, to the SERP. The following table sets forth the components of net periodic benefit costs for the defined benefit plans: Three Months Ended Six Months Ended June 30 June 30 (In thousands) 2018 2017 2018 2017 Service cost $ 1,312 $ 1,049 $ 2,659 $ 2,116 Interest cost 1,039 945 2,105 1,907 Expected return on plan assets (1,500 ) (1,343 ) (3,040 ) (2,711 ) Recognized actuarial gain (12 ) (48 ) (24 ) (97 ) Net periodic benefit cost $ 839 $ 603 $ 1,700 $ 1,215 In accordance with ASU 2017-07, as described in Note 2, the service cost of $1.3 million and $2.7 million for the three and six months ended June 30, 2018 , respectively, was reported as a component of selling, general and administrative expenses. The other components of net periodic benefit cost totaling a net benefit of $0.5 million and $1.0 million for the three and six months ended June 30, 2018 , respectively, were presented as a component of net interest and other, as described in Note 9 below. For the three and six months ended June 30, 2017 , the Company reclassified a net benefit of $0.5 million and $0.9 million , respectively, from selling, general and administrative expenses to net interest and other. The Company used the amounts disclosed in Note 7 of the Notes to Condensed Consolidated Financial Statements in the Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2017 as the estimation basis for applying the retrospective presentation requirements.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	6 Months Ended
	Jun. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	10. COMMITMENTS AND CONTINGENCIES From time to time, a number of lawsuits and claims have been or may be asserted against us relating to the conduct of our business, including routine litigation relating to commercial and employment matters. The outcome of any litigation cannot be predicted with certainty, and some lawsuits may be determined adversely to us. However, management does not believe that the ultimate outcome of any such pending matters is likely to have a material adverse effect on our financial condition or liquidity, although the resolution in any fiscal period of one or more of these matters may have a material adverse effect on our results of operations for that period.

INCOME TAXES

INCOME TAXES	6 Months Ended
	Jun. 30, 2018
Income Tax Disclosure [Abstract]
INCOME TAXES	11. INCOME TAXES The effective tax rate for the three and six months ended June 30, 2018 was 21.5% and 20.7% , respectively. The effective tax rate for the three and six months ended June 30, 2017 was 25.3% and 25.1% , respectively. WESCO’s effective tax rate is typically impacted by the tax effect of intercompany financing, foreign tax rate differences, other nondeductible expenses and state income taxes. The effective tax rates for the current year periods are lower than the prior year periods primarily due to the Tax Cuts and Jobs Act of 2017 (the "TCJA"), which permanently reduced the U.S. federal statutory income tax rate from 35% to 21% , effective January 1, 2018. The unaudited condensed consolidated financial information presented herein reflects provisional amounts for certain income tax effects of the TCJA for which the accounting is incomplete, but a reasonable estimate can be determined, based on enacted tax laws and rates as of June 30, 2018 . On August 1, 2018, the Internal Revenue Service issued proposed regulations regarding Section 965 of the Internal Revenue Code, as amended by the TCJA. We are currently reviewing the proposed regulations and future adjustments (if any) will be recognized as discrete income tax expense or benefit in the period the adjustments are determined.

OTHER FINANCIAL INFORMATION

OTHER FINANCIAL INFORMATION	6 Months Ended
	Jun. 30, 2018
Condensed Financial Information [Abstract]
OTHER FINANCIAL INFORMATION	12. 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, WESCO Distribution and the non-guarantor subsidiaries is presented in the following tables. Condensed Consolidating Balance Sheet June 30, 2018 (In thousands) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Cash and cash equivalents $ — $ 51,489 $ 59,451 $ — $ 110,940 Trade accounts receivable, net — — 1,257,330 — 1,257,330 Inventories — 418,944 516,287 — 935,231 Prepaid expenses and other current assets 4,943 23,741 129,279 (14,524 ) 143,439 Total current assets 4,943 494,174 1,962,347 (14,524 ) 2,446,940 Intercompany receivables, net — — 2,252,907 (2,252,907 ) — Property, buildings and equipment, net — 55,181 102,311 — 157,492 Intangible assets, net — 2,451 338,128 — 340,579 Goodwill — 257,623 1,487,071 — 1,744,694 Investments in affiliates 3,101,741 5,062,631 — (8,164,372 ) — Other assets — 2,780 22,501 — 25,281 Total assets $ 3,106,684 $ 5,874,840 $ 6,165,265 $ (10,431,803 ) $ 4,714,986 Accounts payable $ — $ 423,735 $ 394,444 $ — $ 818,179 Short-term debt — — 35,527 — 35,527 Other current liabilities — 43,599 143,128 (14,524 ) 172,203 Total current liabilities — 467,334 573,099 (14,524 ) 1,025,909 Intercompany payables, net 931,797 1,321,110 — (2,252,907 ) — Long-term debt, net — 867,229 394,476 — 1,261,705 Other noncurrent liabilities 3,820 117,426 140,371 — 261,617 Total WESCO International stockholders' equity 2,171,067 3,101,741 5,062,631 (8,164,372 ) 2,171,067 Noncontrolling interests — — (5,312 ) — (5,312 ) Total liabilities and stockholders’ equity $ 3,106,684 $ 5,874,840 $ 6,165,265 $ (10,431,803 ) $ 4,714,986 Condensed Consolidating Balance Sheet December 31, 2017 (In thousands) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Cash and cash equivalents $ — $ 50,602 $ 67,351 $ — $ 117,953 Trade accounts receivable, net — — 1,170,080 — 1,170,080 Inventories — 430,092 526,056 — 956,148 Prepaid expenses and other current assets 4,730 42,547 152,531 (35,140 ) 164,668 Total current assets 4,730 523,241 1,916,018 (35,140 ) 2,408,849 Intercompany receivables, net — — 2,189,136 (2,189,136 ) — Property, buildings and equipment, net — 50,198 106,247 — 156,445 Intangible assets, net — 2,770 364,334 — 367,104 Goodwill — 257,623 1,514,254 — 1,771,877 Investments in affiliates 3,058,613 5,023,826 — (8,082,439 ) — Other assets — 2,778 28,415 — 31,193 Total assets $ 3,063,343 $ 5,860,436 $ 6,118,404 $ (10,306,715 ) $ 4,735,468 Accounts payable $ — $ 417,690 $ 381,830 $ — $ 799,520 Short-term debt — — 34,075 — 34,075 Other current liabilities — 80,039 162,475 (35,140 ) 207,374 Total current liabilities — 497,729 578,380 (35,140 ) 1,040,969 Intercompany payables, net 939,784 1,249,352 — (2,189,136 ) — Long-term debt, net — 934,033 379,228 — 1,313,261 Other noncurrent liabilities 3,820 120,709 140,566 — 265,095 Total WESCO International stockholders' equity 2,119,739 3,058,613 5,023,826 (8,082,439 ) 2,119,739 Noncontrolling interests — — (3,596 ) — (3,596 ) Total liabilities and stockholders’ equity $ 3,063,343 $ 5,860,436 $ 6,118,404 $ (10,306,715 ) $ 4,735,468 Condensed Consolidating Statement of Income and Comprehensive Income Three Months Ended June 30, 2018 (In thousands) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 921,075 $ 1,222,369 $ (39,450 ) $ 2,103,994 Cost of goods sold (excluding depreciation and amortization) — 746,373 997,177 (39,450 ) 1,704,100 Selling, general and administrative expenses — 147,566 145,322 — 292,888 Depreciation and amortization — 4,656 11,167 — 15,823 Results of affiliates’ operations 57,673 51,122 — (108,795 ) — Net interest and other — 14,259 3,482 — 17,741 Income tax expense — 1,670 14,099 — 15,769 Net income 57,673 57,673 51,122 (108,795 ) 57,673 Net loss attributable to noncontrolling interests — — (267 ) — (267 ) Net income attributable to WESCO International $ 57,673 $ 57,673 $ 51,389 $ (108,795 ) $ 57,940 Other comprehensive income: Foreign currency translation adjustments (28,715 ) (28,715 ) (28,715 ) 57,430 (28,715 ) Comprehensive income attributable to WESCO International $ 28,958 $ 28,958 $ 22,674 $ (51,365 ) $ 29,225 Condensed Consolidating Statement of Income and Comprehensive Income Six Months Ended June 30, 2018 (In thousands) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 1,803,474 $ 2,372,479 $ (78,044 ) $ 4,097,909 Cost of goods sold (excluding depreciation and amortization) — 1,462,631 1,933,479 (78,044 ) 3,318,066 Selling, general and administrative expenses — 298,047 285,670 — 583,717 Depreciation and amortization — 9,275 22,428 — 31,703 Results of affiliates’ operations 100,644 96,325 — (196,969 ) — Net interest and other — 28,076 9,448 — 37,524 Income tax expense — 1,126 25,129 — 26,255 Net income 100,644 100,644 96,325 (196,969 ) 100,644 Net loss attributable to noncontrolling interests — — (1,717 ) — (1,717 ) Net income attributable to WESCO International $ 100,644 $ 100,644 $ 98,042 $ (196,969 ) $ 102,361 Other comprehensive loss: Foreign currency translation adjustments (57,515 ) (57,515 ) (57,515 ) 115,030 (57,515 ) Comprehensive income attributable to WESCO International $ 43,129 $ 43,129 $ 40,527 $ (81,939 ) $ 44,846 Condensed Consolidating Statement of Income and Comprehensive Income Three Months Ended June 30, 2017 (In thousands) 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 — 134,730 133,005 — 267,735 Depreciation and amortization — 4,583 11,138 — 15,721 Results of affiliates’ operations 49,535 40,753 — (90,288 ) — Net interest and other — 28,518 (12,149 ) — 16,369 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 $ 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 $ 82,916 $ 68,619 $ 88,406 $ (157,050 ) $ 82,891 Reclassification As described in Note 8, the Company reclassified a net benefit of $0.5 million from selling, general and administrative expenses to net interest and other in the previously reported Condensed Consolidated Statement of Income and Comprehensive Income of the non-guarantor subsidiaries for the three months ended June 30, 2017 . Condensed Consolidating Statement of Income and Comprehensive Income Six Months Ended June 30, 2017 (In thousands) 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 — 269,986 265,167 — 535,153 Depreciation and amortization — 9,336 22,350 — 31,686 Results of affiliates’ operations 87,334 75,181 — (162,515 ) — Net interest and other — 49,525 (16,889 ) — 32,636 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 $ 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 adjustments, net of tax 252 252 252 (504 ) 252 Comprehensive income attributable to WESCO International $ 132,535 $ 111,750 $ 141,071 $ (252,917 ) $ 132,439 Reclassification As described in Note 8, the Company reclassified a net benefit of $0.9 million from selling, general and administrative expenses to net interest and other in the previously reported Condensed Consolidated Statement of Income and Comprehensive Income of the non-guarantor subsidiaries for the six months ended June 30, 2017 . Condensed Consolidating Statement of Cash Flows Six Months Ended June 30, 2018 (In thousands) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net cash provided by operating activities $ 9,878 $ 31,192 $ 45,751 $ — $ 86,821 Investing activities: Capital expenditures — (9,334 ) (7,050 ) — (16,384 ) Dividends received from subsidiaries — 95,511 — (95,511 ) — Other — (37,524 ) (8,684 ) 37,524 (8,684 ) Net cash provided by (used in) investing activities — 48,653 (15,734 ) (57,987 ) (25,068 ) Financing activities: Borrowings — 191,888 736,372 (45,511 ) 882,749 Repayments (7,987 ) (260,888 ) (673,761 ) 7,987 (934,649 ) Repurchases of common stock (1,891 ) — — — (1,891 ) Decrease in bank overdrafts — — — — — Dividends paid by subsidiaries — — (95,511 ) 95,511 — Other — (9,958 ) — — (9,958 ) Net cash used in financing activities (9,878 ) (78,958 ) (32,900 ) 57,987 (63,749 ) Effect of exchange rate changes on cash and cash equivalents — — (5,017 ) — (5,017 ) Net change in cash and cash equivalents — 887 (7,900 ) — (7,013 ) Cash and cash equivalents at the beginning of period — 50,602 67,351 — 117,953 Cash and cash equivalents at the end of period $ — $ 51,489 $ 59,451 $ — $ 110,940 Condensed Consolidating Statement of Cash Flows Six Months Ended June 30, 2017 (In thousands) 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 ) Increase in bank overdrafts — — — — — 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

Subsequent Events SUBSEQUENT EV

Subsequent Events SUBSEQUENT EVENTS (Notes)	6 Months Ended
	Jun. 30, 2018
Subsequent Events [Abstract]
Subsequent Events [Text Block]	13. 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, 2018
Goodwill [Line Items]
Goodwill Disclosure [Text Block]	5. GOODWILL The following table sets forth the changes in the carrying value of goodwill: Six Months Ended June 30 (In thousands) 2018 2017 Beginning balance January 1 $ 1,771,877 $ 1,720,714 Foreign currency exchange rate changes (27,183 ) 20,826 Ending balance June 30 $ 1,744,694 $ 1,741,540

NET INTEREST AND OTHER (Notes)

NET INTEREST AND OTHER (Notes)	6 Months Ended
	Jun. 30, 2018
Other Income and Expenses [Abstract]
Other Nonoperating Income and Expense [Text Block]	9. NET INTEREST AND OTHER Net interest and other includes interest expense, interest income, amortization of debt discount and debt issuance costs, the non-service cost components of net periodic benefit cost, and foreign exchange gains and losses from the remeasurement of certain financial instruments. For the three and six months ended June 30, 2018 , a foreign exchange gain of $0.4 million and a foreign exchange loss of $2.6 million , respectively, from the remeasurement of financial instruments were reported as a component of net interest and other. Foreign exchange gains and losses were not material for the three and six months ended June 30, 2017 .

ACCOUNTING POLICIES (Policies)

ACCOUNTING POLICIES (Policies)	6 Months Ended
	Jun. 30, 2018
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 2017 Annual Report on Form 10-K as filed with the SEC on February 22, 2018. The Condensed Consolidated Balance Sheet at December 31, 2017 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, 2018 , the unaudited Condensed Consolidated Statements of Income and Comprehensive Income for the six months ended June 30, 2018 and 2017 , respectively, and the unaudited Condensed Consolidated Statements of Cash Flows for the six months ended June 30, 2018 and 2017 , 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.
Reclassifications [Text Block]	Reclassifications Effective January 1, 2018, WESCO adopted Accounting Standards Update (ASU) 2017-07, Compensation—Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost . The adoption of this ASU, as described below and in Note 8, resulted in the reclassification of amounts reported in the unaudited Condensed Consolidated Statements of Income and Comprehensive Income for the three and six months ended June 30, 2017 .
Fair Value of Financial Instruments	4. FAIR VALUE OF FINANCIAL INSTRUMENTS The Company’s financial instruments consist of cash and cash equivalents, accounts receivable, accounts payable, bank overdrafts, and outstanding indebtedness. The reported carrying amounts of WESCO's financial instruments approximated their fair values as of June 30, 2018 and December 31, 2017 . The Company uses a market approach to determine the fair value of its debt instruments, utilizing quoted prices in active markets, interest rates and other relevant information generated by market transactions involving similar instruments. Therefore, the Company's debt instruments are classified as Level 2 within the fair value hierarchy.
New Accounting Pronouncements, Policy [Policy Text Block]	Recently Adopted Accounting Pronouncements Effective January 1, 2018, WESCO adopted ASU 2014-09, Revenue from Contracts with Customers , and all the related amendments (“Topic 606”) using the modified retrospective approach to all open contracts. There was no impact to WESCO’s previously reported consolidated financial statements and WESCO does not expect the adoption of Topic 606 to have a material impact on its revenue and results of operations on an ongoing basis. WESCO’s significant accounting policies are disclosed in Note 2 of the Notes to Consolidated Financial Statements in the Annual Report on Form 10-K for the year ended December 31, 2017. Changes to the Company’s significant accounting policies as a result of adopting Topic 606 are described in Note 3 below. In August 2016, the Financial Accounting Standards Board (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 Company adopted this ASU in the first quarter of 2018. The adoption of this guidance did not have an impact on the unaudited condensed consolidated financial information presented herein. 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 . This ASU requires that an employer disaggregate the service cost from the other components of net benefit cost. The Company adopted this guidance on a retrospective basis in the first quarter of 2018. See Note 8 for a description of the impact of this accounting standard on the unaudited Condensed Consolidated Statements of Income and Comprehensive Income presented herein. The adoption of this guidance did not have an impact on the Company's unaudited Condensed Consolidated Balance Sheets and the unaudited Condensed Consolidated Statements of Cash Flows presented herein. In May 2017, the FASB issued ASU 2017-09, Compensation—Stock Compensation (Topic 718): Scope of Modification Accounting. This ASU 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 Company adopted this ASU in the first quarter of 2018. The adoption of this guidance did not have an impact on the unaudited condensed consolidated financial information presented herein. Recently Issued Accounting Pronouncements 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 in the balance sheet and disclosing key information about leasing arrangements. This ASU 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 has established a cross-functional team to evaluate and implement the new standard. The team is currently in the process of gathering lease data and selecting a third-party software solution to assist with accounting for leases under the new standard. Upon adoption, right-of-use assets and lease liabilities will be recorded in the Consolidated Balance Sheets. 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 this ASU are effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted. Management does not expect the adoption of this accounting standard to have a material impact on its 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 of the goodwill impairment test. Under the amendments in this ASU, 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 expects to adopt this ASU in the fourth quarter of 2018 when the Company performs its annual impairment testing. The Company does not expect the adoption of this accounting standard to have a material impact on its 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, 2018
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, 2018 and 2017 , 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 8,402 — 499,631 443,731 Weighted-average fair value $ 17.85 $ — $ 18.39 $ 20.65 Restricted stock units granted 2,502 — 116,771 98,680 Weighted-average fair value $ 59.95 $ — $ 62.75 $ 71.65 Performance-based awards granted — — 44,144 39,978 Weighted-average fair value $ — $ — $ 62.80 $ 76.63
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, 2018 : Awards Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (In years) Aggregate Intrinsic Value (In thousands) Outstanding at December 31, 2017 2,238,607 $ 57.75 Granted 499,631 62.76 Exercised (158,279 ) 39.63 Forfeited (135,511 ) 68.78 Outstanding at June 30, 2018 2,444,448 59.33 6.6 $ 13,624 Exercisable at June 30, 2018 1,523,126 $ 58.09 5.2 $ 11,130
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, 2018 : Awards Weighted- Average Fair Value Unvested at December 31, 2017 290,054 $ 58.11 Granted 116,771 62.75 Vested (57,175 ) 69.44 Forfeited (10,710 ) 56.45 Unvested at June 30, 2018 338,940 $ 57.85
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, 2018 : Awards Weighted- Average Fair Value Unvested at December 31, 2017 148,508 $ 60.23 Granted 44,144 62.80 Vested — — Forfeited (52,342 ) 65.31 Unvested at June 30, 2018 140,310 $ 59.33
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 2.8 % n/a 2.5 % 1.9 % Expected life (in years) 5 n/a 5 5 Expected volatility 28 % n/a 28 % 29 %
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, 2018 and 2017 was estimated using the following weighted-average assumptions: Six Months Ended June 30, June 30, Grant date share price $ 62.80 $ 71.65 WESCO expected volatility n/a 29 % Peer group median volatility n/a 24 % Risk-free interest rate n/a 1.5 % Correlation of peer company returns n/a 114 %

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	6 Months Ended
	Jun. 30, 2018
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) 2018 2017 2018 2017 Net income attributable to WESCO International $ 57,940 $ 49,510 $ 102,361 $ 87,238 Weighted-average common shares outstanding used in computing basic earnings per share 47,085 48,294 47,062 48,499 Common shares issuable upon exercise of dilutive equity awards 465 482 516 582 Weighted-average common shares outstanding and common share equivalents used in computing diluted earnings per share 47,550 48,776 47,578 49,081 Earnings per share attributable to WESCO International Basic $ 1.23 $ 1.03 $ 2.18 $ 1.80 Diluted $ 1.22 $ 1.02 $ 2.15 $ 1.78

EMPLOYEE BENEFIT PLANS Schedule

EMPLOYEE BENEFIT PLANS Schedule of Net Benefit Costs (Tables)	6 Months Ended
	Jun. 30, 2018
Postemployment Benefits [Abstract]
Schedule of Net Benefit Costs [Table Text Block]	The following table sets forth the components of net periodic benefit costs for the defined benefit plans: Three Months Ended Six Months Ended June 30 June 30 (In thousands) 2018 2017 2018 2017 Service cost $ 1,312 $ 1,049 $ 2,659 $ 2,116 Interest cost 1,039 945 2,105 1,907 Expected return on plan assets (1,500 ) (1,343 ) (3,040 ) (2,711 ) Recognized actuarial gain (12 ) (48 ) (24 ) (97 ) Net periodic benefit cost $ 839 $ 603 $ 1,700 $ 1,215

OTHER FINANCIAL INFORMATION (Ta

OTHER FINANCIAL INFORMATION (Tables)	6 Months Ended
	Jun. 30, 2018
Condensed Balance Sheet Statements, Captions [Line Items]
Condensed Balance Sheet [Table Text Block]	Condensed Consolidating Balance Sheet June 30, 2018 (In thousands) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Cash and cash equivalents $ — $ 51,489 $ 59,451 $ — $ 110,940 Trade accounts receivable, net — — 1,257,330 — 1,257,330 Inventories — 418,944 516,287 — 935,231 Prepaid expenses and other current assets 4,943 23,741 129,279 (14,524 ) 143,439 Total current assets 4,943 494,174 1,962,347 (14,524 ) 2,446,940 Intercompany receivables, net — — 2,252,907 (2,252,907 ) — Property, buildings and equipment, net — 55,181 102,311 — 157,492 Intangible assets, net — 2,451 338,128 — 340,579 Goodwill — 257,623 1,487,071 — 1,744,694 Investments in affiliates 3,101,741 5,062,631 — (8,164,372 ) — Other assets — 2,780 22,501 — 25,281 Total assets $ 3,106,684 $ 5,874,840 $ 6,165,265 $ (10,431,803 ) $ 4,714,986 Accounts payable $ — $ 423,735 $ 394,444 $ — $ 818,179 Short-term debt — — 35,527 — 35,527 Other current liabilities — 43,599 143,128 (14,524 ) 172,203 Total current liabilities — 467,334 573,099 (14,524 ) 1,025,909 Intercompany payables, net 931,797 1,321,110 — (2,252,907 ) — Long-term debt, net — 867,229 394,476 — 1,261,705 Other noncurrent liabilities 3,820 117,426 140,371 — 261,617 Total WESCO International stockholders' equity 2,171,067 3,101,741 5,062,631 (8,164,372 ) 2,171,067 Noncontrolling interests — — (5,312 ) — (5,312 ) Total liabilities and stockholders’ equity $ 3,106,684 $ 5,874,840 $ 6,165,265 $ (10,431,803 ) $ 4,714,986 Condensed Consolidating Balance Sheet December 31, 2017 (In thousands) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Cash and cash equivalents $ — $ 50,602 $ 67,351 $ — $ 117,953 Trade accounts receivable, net — — 1,170,080 — 1,170,080 Inventories — 430,092 526,056 — 956,148 Prepaid expenses and other current assets 4,730 42,547 152,531 (35,140 ) 164,668 Total current assets 4,730 523,241 1,916,018 (35,140 ) 2,408,849 Intercompany receivables, net — — 2,189,136 (2,189,136 ) — Property, buildings and equipment, net — 50,198 106,247 — 156,445 Intangible assets, net — 2,770 364,334 — 367,104 Goodwill — 257,623 1,514,254 — 1,771,877 Investments in affiliates 3,058,613 5,023,826 — (8,082,439 ) — Other assets — 2,778 28,415 — 31,193 Total assets $ 3,063,343 $ 5,860,436 $ 6,118,404 $ (10,306,715 ) $ 4,735,468 Accounts payable $ — $ 417,690 $ 381,830 $ — $ 799,520 Short-term debt — — 34,075 — 34,075 Other current liabilities — 80,039 162,475 (35,140 ) 207,374 Total current liabilities — 497,729 578,380 (35,140 ) 1,040,969 Intercompany payables, net 939,784 1,249,352 — (2,189,136 ) — Long-term debt, net — 934,033 379,228 — 1,313,261 Other noncurrent liabilities 3,820 120,709 140,566 — 265,095 Total WESCO International stockholders' equity 2,119,739 3,058,613 5,023,826 (8,082,439 ) 2,119,739 Noncontrolling interests — — (3,596 ) — (3,596 ) Total liabilities and stockholders’ equity $ 3,063,343 $ 5,860,436 $ 6,118,404 $ (10,306,715 ) $ 4,735,468

OTHER FINANCIAL INFORMATION Con

OTHER FINANCIAL INFORMATION Condensed Income Statement (Tables)	6 Months Ended
	Jun. 30, 2018
Condensed Income Statements, Captions [Line Items]
Condensed Income Statement [Table Text Block]	Condensed Consolidating Statement of Income and Comprehensive Income Three Months Ended June 30, 2017 (In thousands) 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 — 134,730 133,005 — 267,735 Depreciation and amortization — 4,583 11,138 — 15,721 Results of affiliates’ operations 49,535 40,753 — (90,288 ) — Net interest and other — 28,518 (12,149 ) — 16,369 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 $ 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 $ 82,916 $ 68,619 $ 88,406 $ (157,050 ) $ 82,891 Condensed Consolidating Statement of Income and Comprehensive Income Six Months Ended June 30, 2017 (In thousands) 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 — 269,986 265,167 — 535,153 Depreciation and amortization — 9,336 22,350 — 31,686 Results of affiliates’ operations 87,334 75,181 — (162,515 ) — Net interest and other — 49,525 (16,889 ) — 32,636 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 $ 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 adjustments, net of tax 252 252 252 (504 ) 252 Comprehensive income attributable to WESCO International $ 132,535 $ 111,750 $ 141,071 $ (252,917 ) $ 132,439 Condensed Consolidating Statement of Income and Comprehensive Income Six Months Ended June 30, 2018 (In thousands) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 1,803,474 $ 2,372,479 $ (78,044 ) $ 4,097,909 Cost of goods sold (excluding depreciation and amortization) — 1,462,631 1,933,479 (78,044 ) 3,318,066 Selling, general and administrative expenses — 298,047 285,670 — 583,717 Depreciation and amortization — 9,275 22,428 — 31,703 Results of affiliates’ operations 100,644 96,325 — (196,969 ) — Net interest and other — 28,076 9,448 — 37,524 Income tax expense — 1,126 25,129 — 26,255 Net income 100,644 100,644 96,325 (196,969 ) 100,644 Net loss attributable to noncontrolling interests — — (1,717 ) — (1,717 ) Net income attributable to WESCO International $ 100,644 $ 100,644 $ 98,042 $ (196,969 ) $ 102,361 Other comprehensive loss: Foreign currency translation adjustments (57,515 ) (57,515 ) (57,515 ) 115,030 (57,515 ) Comprehensive income attributable to WESCO International $ 43,129 $ 43,129 $ 40,527 $ (81,939 ) $ 44,846 Condensed Consolidating Statement of Income and Comprehensive Income Six Months Ended June 30, 2018 (In thousands) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 1,803,474 $ 2,372,479 $ (78,044 ) $ 4,097,909 Cost of goods sold (excluding depreciation and amortization) — 1,462,631 1,933,479 (78,044 ) 3,318,066 Selling, general and administrative expenses — 298,047 285,670 — 583,717 Depreciation and amortization — 9,275 22,428 — 31,703 Results of affiliates’ operations 100,644 96,325 — (196,969 ) — Net interest and other — 28,076 9,448 — 37,524 Income tax expense — 1,126 25,129 — 26,255 Net income 100,644 100,644 96,325 (196,969 ) 100,644 Net loss attributable to noncontrolling interests — — (1,717 ) — (1,717 ) Net income attributable to WESCO International $ 100,644 $ 100,644 $ 98,042 $ (196,969 ) $ 102,361 Other comprehensive loss: Foreign currency translation adjustments (57,515 ) (57,515 ) (57,515 ) 115,030 (57,515 ) Comprehensive income attributable to WESCO International $ 43,129 $ 43,129 $ 40,527 $ (81,939 ) $ 44,846 Condensed Consolidating Statement of Income and Comprehensive Income Three Months Ended June 30, 2018 (In thousands) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 921,075 $ 1,222,369 $ (39,450 ) $ 2,103,994 Cost of goods sold (excluding depreciation and amortization) — 746,373 997,177 (39,450 ) 1,704,100 Selling, general and administrative expenses — 147,566 145,322 — 292,888 Depreciation and amortization — 4,656 11,167 — 15,823 Results of affiliates’ operations 57,673 51,122 — (108,795 ) — Net interest and other — 14,259 3,482 — 17,741 Income tax expense — 1,670 14,099 — 15,769 Net income 57,673 57,673 51,122 (108,795 ) 57,673 Net loss attributable to noncontrolling interests — — (267 ) — (267 ) Net income attributable to WESCO International $ 57,673 $ 57,673 $ 51,389 $ (108,795 ) $ 57,940 Other comprehensive income: Foreign currency translation adjustments (28,715 ) (28,715 ) (28,715 ) 57,430 (28,715 ) Comprehensive income attributable to WESCO International $ 28,958 $ 28,958 $ 22,674 $ (51,365 ) $ 29,225

OTHER FINANCIAL INFORMATION C24

OTHER FINANCIAL INFORMATION Condensed Cash Flow Statement (Tables)	6 Months Ended
	Jun. 30, 2018
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) 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 ) Increase in bank overdrafts — — — — — 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, 2018 (In thousands) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net cash provided by operating activities $ 9,878 $ 31,192 $ 45,751 $ — $ 86,821 Investing activities: Capital expenditures — (9,334 ) (7,050 ) — (16,384 ) Dividends received from subsidiaries — 95,511 — (95,511 ) — Other — (37,524 ) (8,684 ) 37,524 (8,684 ) Net cash provided by (used in) investing activities — 48,653 (15,734 ) (57,987 ) (25,068 ) Financing activities: Borrowings — 191,888 736,372 (45,511 ) 882,749 Repayments (7,987 ) (260,888 ) (673,761 ) 7,987 (934,649 ) Repurchases of common stock (1,891 ) — — — (1,891 ) Decrease in bank overdrafts — — — — — Dividends paid by subsidiaries — — (95,511 ) 95,511 — Other — (9,958 ) — — (9,958 ) Net cash used in financing activities (9,878 ) (78,958 ) (32,900 ) 57,987 (63,749 ) Effect of exchange rate changes on cash and cash equivalents — — (5,017 ) — (5,017 ) Net change in cash and cash equivalents — 887 (7,900 ) — (7,013 ) Cash and cash equivalents at the beginning of period — 50,602 67,351 — 117,953 Cash and cash equivalents at the end of period $ — $ 51,489 $ 59,451 $ — $ 110,940

GOODWILL (Tables)

GOODWILL (Tables)	6 Months Ended
	Jun. 30, 2018
Goodwill [Line Items]
Schedule of Goodwill [Table Text Block]	Six Months Ended June 30 (In thousands) 2018 2017 Beginning balance January 1 $ 1,771,877 $ 1,720,714 Foreign currency exchange rate changes (27,183 ) 20,826 Ending balance June 30 $ 1,744,694 $ 1,741,540

REVENUE (Tables)

REVENUE (Tables)	6 Months Ended
	Jun. 30, 2018
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue [Table Text Block]	The following tables disaggregate WESCO’s revenue by end market and geography: Three Months Ended Six Months Ended June 30 June 30 (In thousands) 2018 2017 2018 2017 Industrial $ 760,741 $ 711,305 $ 1,519,723 $ 1,389,601 Construction 683,752 623,763 1,321,551 1,195,392 Utility 336,961 282,400 652,506 548,660 Commercial, Institutional and Government ("CIG") 322,540 292,156 604,129 548,562 Total by end market $ 2,103,994 $ 1,909,624 $ 4,097,909 $ 3,682,215 Three Months Ended Six Months Ended June 30 June 30 (In thousands) 2018 2017 2018 2017 United States $ 1,563,392 $ 1,451,401 $ 3,046,140 $ 2,794,601 Other (1) 540,602 458,223 1,051,769 887,614 Total by geography $ 2,103,994 $ 1,909,624 $ 4,097,909 $ 3,682,215 (1) Other primarily includes net sales to customers in Canada.
Revenue Recognition, Revenue Reductions [Policy Text Block]	WESCO’s revenues are adjusted for variable consideration, which includes customer volume rebates, returns, and discounts. WESCO measures variable consideration by estimating expected outcomes using analysis and inputs based upon anticipated performance, historical data, as well as current and forecasted information. Measurement and recognition of variable consideration is reviewed by management on a monthly basis and revenue is adjusted accordingly. Variable consideration reduced revenue for the three months ended June 30, 2018 and 2017 by approximately $25.0 million and $21.7 million , respectively, and by approximately $49.4 million and $42.3 million for the six months ended June 30, 2018 and 2017 , respectively.

ORGANIZATION (Details)

ORGANIZATION (Details)	Jun. 30, 2018customerscountriesbranches
Restructuring Cost and Reserve [Line Items]
Active customers (in customers) | customers	70,000
Full service branches (in branches) | branches	500
Additional countries (in countries) | countries	16

ACCOUNTING POLICIES (Details)

ACCOUNTING POLICIES (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Prepaid expenses and other current assets	$ 81,078	$ 63,439
Assets, Current	2,446,940	2,408,849
Goodwill	1,744,694	1,771,877	$ 1,741,540	$ 1,720,714
Liabilities and Equity	4,714,986	4,735,468
Other Accrued Liabilities, Current	88,366	95,820
Liabilities, Current	1,025,909	1,040,969
Assets	4,714,986	4,735,468
Deferred Tax Liabilities, Net, Noncurrent	140,498	136,858
Liabilities	2,549,231	2,619,325
Retained earnings	2,182,484	2,079,697
Accumulated other comprehensive income	(370,105)	(312,590)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 2,165,755	$ 2,116,143

ACQUISITIONS - ACQUISITIONS (De

ACQUISITIONS - ACQUISITIONS (Details)	Jun. 30, 2018branches
Business Acquisition [Line Items]
Number of Stores	500

SCHEDULE OF SHARE-BASED COMPENS

SCHEDULE OF SHARE-BASED COMPENSATION, STOCK OPTIONS AND STOCK APPRECIATION RIGHTS AWARD ACTIVITY (Details) - Stock Appreciation Rights (SARs) [Member] - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
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			$ 62.76
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	$ 11,130		$ 11,130
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$ 59.33		$ 59.33		$ 57.75
Share-based Compensation Arrangement By Share-based Payment Award, Options and Stock Appreciation Rights, Outstanding [Roll Forward]
Beginning of Year (in shares)	1,523,126		1,523,126
Grants in Period (in shares)	8,402	0	499,631	443,731
Exercises in Period (in shares)			158,279
Forfeitures in Period (in shares)			135,511
Weighted Average Exercise Price, Exercises in Period (in dollars per share)			$ 39.63
Weighted Average Exercise Price, Forfeitures in Period (in dollars per share)			68.78
Weighted Average Exercise Price, Exercisable (in dollars per share)	$ 58.09		$ 58.09
Weighted Average Remaining Contractual Term, Outstanding (in years)			6 years 7 months
Weighted Average Remaining Contractual Term, Exercisable (in years)			5 years 2 months
Aggregate Intrinsic Value, Outstanding	$ 13,624		$ 13,624
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number	2,444,448		2,444,448		2,238,607

SCHEDULE OF SHARE-BASED PAYMENT

SCHEDULE OF SHARE-BASED PAYMENT AWARD, VALUATION ASSUMPTIONS (Details) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate	2.80%		2.50%	1.90%
Expected life (in years)	5 years		5 years	5 years
WESCO expected volatility	28.00%		28.00%	29.00%
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	8,402	0	499,631	443,731
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 17.85	$ 0	$ 18.39	$ 20.65
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	2,502	0	116,771	98,680
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 59.95	$ 0	$ 62.75	$ 71.65
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	0	0	44,144	39,978
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	$ 62.80	$ 76.63
Risk free interest rate				0.00%
WESCO expected volatility				0.00%

SUMMARY OF RESTRICTED STOCK UNI

SUMMARY OF RESTRICTED STOCK UNITS (Details) - Restricted Stock Units (RSUs) [Member] - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Unvested (in shares)	338,940		338,940		290,054
Granted (in shares)	2,502	0	116,771	98,680
Vested (in shares)			(57,175)
Forfeited (in shares)			(10,710)
Unvested, Weighted Average Fair Value (in dollars per share)	$ 57.85		$ 57.85		$ 58.11
Granted, Weighted Average Fair Value (in dollars per share)	$ 59.95	$ 0	62.75	$ 71.65
Vested in Period, Weighted Average Fair Value (in dollars per share)			69.44
Forfeited in Period, Weighted Average Fair Value (in dollars per share)			$ 56.45

SUMMARY OF PERFORMANCE-BASED AW

SUMMARY OF PERFORMANCE-BASED AWARDS (Details) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Unvested (in shares)	140,310		140,310		148,508
Granted (in shares)	0	0	44,144	39,978
Vested (in shares)			0
Forfeited (in shares)			(52,342)
Unvested, Weighted Average Fair Value (in dollars per share)	$ 59.33		$ 59.33		$ 60.23
Granted, Weighted Average Fair Value (in dollars per share)	$ 0	$ 0	62.80	$ 76.63
Vested in Period, Weighted Average Fair Value (in dollars per share)			0
Forfeited in Period, Weighted Average Fair Value (in dollars per share)			$ 65.31
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)	91,505		91,505
Share-based Compensation Award, Tranche Two [Member] | Net Income Growth Rate [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Unvested (in shares)	48,805		48,805
Share-based Compensation Award, Tranche Two [Member] | Earnings Per Share Growth [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Unvested (in shares)	21,350		21,350
Share-based Compensation Award, Tranche Two [Member] | Return on Net Assets [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Unvested (in shares)	21,350		21,350

SCHEDULE OF SHARE-BASED PAYME34

SCHEDULE OF SHARE-BASED PAYMENT AWARD, PERFORMANCE-BASED AWARDS, VALUATION ASSUMPTIONS (Details) - $ / shares	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
WESCO expected volatility	28.00%	28.00%	29.00%
Risk free interest rate	2.80%	2.50%	1.90%
Correlation			0.00%
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Exercise Price	$ 62.80	$ 62.80	$ 71.65
WESCO expected volatility			0.00%
Risk free interest rate			0.00%

STOCK-BASED COMPENSATION (Detai

STOCK-BASED COMPENSATION (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		9 Months Ended	12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2018	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 4.4	$ 4.1	$ 8	$ 7.8
Total unrecognized compensation cost	$ 27		$ 27
Share-based Compensation Award, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance-based awards outstanding (in shares)	48,805		48,805
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)	91,505		91,505
Scenario, Forecast [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense					$ 8.3	$ 0.7	$ 6.3	$ 11.7

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, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Net income (loss) attributable to WESCO International, Inc.	$ 57,940	$ 49,510	$ 102,361	$ 87,238
Weighted average common shares outstanding used in computing basic earnings per share (in shares)	47,085	48,294	47,062	48,499
Common shares issuable upon exercise of dilutive stock options (in shares)	465	482	516	582
Weighted average common shares outstanding and common share equivalents used in computing diluted earnings per share (in shares)	47,550	48,776	47,578	49,081
Earnings Per Share, Basic and Diluted [Abstract]
Basic (in dollars per share)	$ 1.23	$ 1.03	$ 2.18	$ 1.80
Diluted (in dollars per share)	$ 1.22	$ 1.02	$ 2.15	$ 1.78

EARNINGS PER SHARE (Details)

EARNINGS PER SHARE (Details) - shares shares in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Equity Award [Domain]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1.3	1.5	1.2

EARNINGS PER SHARE Accelerated

EARNINGS PER SHARE Accelerated Share Repurchase (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Accelerated Share Repurchases [Line Items]
Payments for Repurchase of Common Stock	$ (1,891)	$ (56,665)
Stock Repurchase Program, Authorized Amount	$ 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)

EMPLOYEE BENEFIT PLANS (Details

EMPLOYEE BENEFIT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Retirement Benefits [Abstract]
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 100		$ 200
Schedule of Employee Benefit Plans [Line Items]
Defined Benefit Plan, Service Cost	1,312	$ 1,049	2,659	$ 2,116
Postemployment Benefits, Period Expense			21,900	$ 10,600
Deferred Compensation Liability, Classified, Noncurrent	$ 24,000		$ 24,000		$ 24,300
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, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 100		$ 200
Service cost	1,312	$ 1,049	2,659	$ 2,116
Interest cost	1,039	945	2,105	1,907
Expected return on plan assets	(1,500)	(1,343)	(3,040)	(2,711)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(12)	(48)	(24)	(97)
Net periodic benefit cost	839	603	1,700	1,215
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Other Nonoperating Gains (Losses)	$ (500)	$ (500)	$ (1,000)	$ (900)

INCOME TAXES (Details)

INCOME TAXES (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Tax Contingency [Line Items]
Effective tax rate	21.50%	25.27418%	20.70%	25.13608%
Federal statutory rate			21.00%

INCOME TAXES Income Tax Rates (

INCOME TAXES Income Tax Rates (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation, Percent	21.50%	25.27418%	20.70%	25.13608%
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			21.00%

OTHER FINANCIAL INFORMATION (De

OTHER FINANCIAL INFORMATION (Details) - Unsecured Debt [Member] $ in Millions	Jun. 30, 2018USD ($)
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, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Condensed Financial Information [Line Items]
Cash and cash equivalents	$ 110,940	$ 117,953	$ 87,799	$ 110,131
Trade accounts receivable, net	1,257,330	1,170,080
Inventories, net	935,231	956,148
Prepaid Expense and Other Assets, Current	81,078	63,439
Total current assets	2,446,940	2,408,849
Property, buildings and equipment, net	157,492	156,445
Intangible assets, net	340,579	367,104
Goodwill and other intangibles, net	1,744,694	1,771,877	1,741,540	1,720,714
Other assets	25,281	31,193
Total assets	4,714,986	4,735,468
Accounts payable	818,179	799,520
Short-term debt	35,527	34,075
Total current liabilities	1,025,909	1,040,969
Long-term Debt, Excluding Current Maturities	1,261,705	1,313,261
Total stockholders' equity	2,171,067	2,119,739
Stockholders' Equity Attributable to Noncontrolling Interest	5,312	3,596
Total liabilities and stockholders' equity	4,714,986	4,735,468
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	4,943	4,730
Total current assets	4,943	4,730
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	3,101,741	3,058,613
Other assets	0	0
Total assets	3,106,684	3,063,343
Accounts payable	0	0
Short-term debt	0	0
Other Liabilities, Current	0	0
Total current liabilities	0	0
Intercompany payables, net	931,797	939,784
Long-term Debt, Excluding Current Maturities	0	0
Liabilities, Other than Long-term Debt, Noncurrent	3,820	3,820
Total stockholders' equity	2,171,067	2,119,739
Stockholders' Equity Attributable to Noncontrolling Interest	0	0
Total liabilities and stockholders' equity	3,106,684	3,063,343
Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Cash and cash equivalents	51,489	50,602	36,138	41,552
Trade accounts receivable, net	0	0
Inventories, net	418,944	430,092
Prepaid Expense and Other Assets, Current	23,741	42,547
Total current assets	494,174	523,241
Intercompany receivables, net	0	0
Property, buildings and equipment, net	55,181	50,198
Intangible assets, net	2,451	2,770
Goodwill and other intangibles, net	257,623	257,623
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	5,062,631	5,023,826
Other assets	2,780	2,778
Total assets	5,874,840	5,860,436
Accounts payable	423,735	417,690
Short-term debt	0	0
Other Liabilities, Current	43,599	80,039
Total current liabilities	467,334	497,729
Intercompany payables, net	1,321,110	1,249,352
Long-term Debt, Excluding Current Maturities	867,229	934,033
Liabilities, Other than Long-term Debt, Noncurrent	117,426	120,709
Total stockholders' equity	3,101,741	3,058,613
Stockholders' Equity Attributable to Noncontrolling Interest	0	0
Total liabilities and stockholders' equity	5,874,840	5,860,436
Non-Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Cash and cash equivalents	59,451	67,351	51,661	68,579
Trade accounts receivable, net	1,257,330	1,170,080
Inventories, net	516,287	526,056
Prepaid Expense and Other Assets, Current	129,279	152,531
Total current assets	1,962,347	1,916,018
Intercompany receivables, net	2,252,907	2,189,136
Property, buildings and equipment, net	102,311	106,247
Intangible assets, net	338,128	364,334
Goodwill and other intangibles, net	1,487,071	1,514,254
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0	0
Other assets	22,501	28,415
Total assets	6,165,265	6,118,404
Accounts payable	394,444	381,830
Short-term debt	35,527	34,075
Other Liabilities, Current	143,128	162,475
Total current liabilities	573,099	578,380
Intercompany payables, net	0	0
Long-term Debt, Excluding Current Maturities	394,476	379,228
Liabilities, Other than Long-term Debt, Noncurrent	140,371	140,566
Total stockholders' equity	5,062,631	5,023,826
Stockholders' Equity Attributable to Noncontrolling Interest	5,312	3,596
Total liabilities and stockholders' equity	6,165,265	6,118,404
Consolidated Entities [Member]
Condensed Financial Information [Line Items]
Cash and cash equivalents	110,940	117,953	87,799	110,131
Trade accounts receivable, net	1,257,330	1,170,080
Inventories, net	935,231	956,148
Prepaid Expense and Other Assets, Current	143,439	164,668
Total current assets	2,446,940	2,408,849
Intercompany receivables, net	0	0
Property, buildings and equipment, net	157,492	156,445
Intangible assets, net	340,579	367,104
Goodwill and other intangibles, net	1,744,694	1,771,877
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0	0
Other assets	25,281	31,193
Total assets	4,714,986	4,735,468
Accounts payable	818,179	799,520
Short-term debt	35,527	34,075
Other Liabilities, Current	172,203	207,374
Total current liabilities	1,025,909	1,040,969
Intercompany payables, net	0	0
Long-term Debt, Excluding Current Maturities	1,261,705	1,313,261
Liabilities, Other than Long-term Debt, Noncurrent	261,617	265,095
Total stockholders' equity	2,171,067	2,119,739
Stockholders' Equity Attributable to Noncontrolling Interest	5,312	3,596
Total liabilities and stockholders' equity	4,714,986	4,735,468
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	(14,524)	(35,140)
Total current assets	(14,524)	(35,140)
Intercompany receivables, net	(2,252,907)	(2,189,136)
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	(8,164,372)	(8,082,439)
Other assets	0	0
Total assets	(10,431,803)	(10,306,715)
Accounts payable	0	0
Short-term debt	0	0
Other Liabilities, Current	(14,524)	(35,140)
Total current liabilities	(14,524)	(35,140)
Intercompany payables, net	(2,252,907)	(2,189,136)
Long-term Debt, Excluding Current Maturities	0	0
Liabilities, Other than Long-term Debt, Noncurrent	0	0
Total stockholders' equity	(8,164,372)	(8,082,439)
Stockholders' Equity Attributable to Noncontrolling Interest	0	0
Total liabilities and stockholders' equity	$ (10,431,803)	$ (10,306,715)

CONDENSED CONSOLIDATED INCOME S

CONDENSED CONSOLIDATED INCOME STATEMENTS (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Condensed Financial Information [Line Items]
Revenues	$ 2,103,994	$ 1,909,624	$ 4,097,909	$ 3,682,215
Cost of goods sold	1,704,100	1,543,510	3,318,066	2,966,083
Selling, general and administrative expense	292,888	267,735	583,717	535,153
Depreciation and amortization	15,823	15,721	31,703	31,686
Provision for income taxes	15,769	16,754	26,255	29,323
Net income (loss)	57,673	49,535	100,644	87,334
Less: Net (loss) income attributable to noncontrolling interest	(267)	25	(1,717)	96
Net income (loss) attributable to WESCO International, Inc.	57,940	49,510	102,361	87,238
Comprehensive Income:
Foreign currency translation adjustment	(28,715)	33,381	(57,515)	44,949
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	0	0	0	252
Comprehensive income attributable to WESCO International, Inc.	29,225	82,891	44,846	132,439
Parent Company [Member]
Condensed Financial Information [Line Items]
Revenues	0	0	0	0
Cost of goods sold	0	0	0	0
Selling, general and administrative expense	0	0	0	0
Depreciation and amortization	0	0	0	0
Income (Loss) from Subsidiaries, before Tax	57,673	49,535	100,644	87,334
Other Nonoperating Income (Expense)	0	0	0	0
Provision for income taxes	0	0	0	0
Net income (loss)	57,673	49,535	100,644	87,334
Less: Net (loss) income attributable to noncontrolling interest	0	0	0	0
Net income (loss) attributable to WESCO International, Inc.	57,673	49,535	100,644	87,334
Comprehensive Income:
Foreign currency translation adjustment	(28,715)	33,381	(57,515)	44,949
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax				(252)
Comprehensive income attributable to WESCO International, Inc.	28,958	82,916	43,129	132,535
Non-Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Revenues	1,222,369	1,100,661	2,372,479	2,120,315
Cost of goods sold	997,177	895,001	1,933,479	1,721,500
Selling, general and administrative expense	145,322	133,005	285,670	265,167
Depreciation and amortization	11,167	11,138	22,428	22,350
Income (Loss) from Subsidiaries, before Tax	0	0	0	0
Other Nonoperating Income (Expense)	3,482	(12,149)	9,448	(16,889)
Provision for income taxes	14,099	18,616	25,129	32,221
Net income (loss)	51,122	55,050	96,325	95,966
Less: Net (loss) income attributable to noncontrolling interest	(267)	25	(1,717)	96
Net income (loss) attributable to WESCO International, Inc.	51,389	55,025	98,042	95,870
Comprehensive Income:
Foreign currency translation adjustment	(28,715)	33,381	(57,515)	44,949
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax				(252)
Comprehensive income attributable to WESCO International, Inc.	22,674	88,406	40,527	141,071
Consolidated Entities [Member]
Condensed Financial Information [Line Items]
Revenues	2,103,994	1,909,624	4,097,909	3,682,215
Cost of goods sold	1,704,100	1,543,510	3,318,066	2,966,083
Selling, general and administrative expense	292,888	267,735	583,717	535,153
Depreciation and amortization	15,823	15,721	31,703	31,686
Income (Loss) from Subsidiaries, before Tax	0	0	0	0
Other Nonoperating Income (Expense)	(17,741)	(16,369)	(37,524)	(32,636)
Provision for income taxes	15,769	16,754	26,255	29,323
Net income (loss)	57,673	49,535	100,644	87,334
Less: Net (loss) income attributable to noncontrolling interest	(267)	25	(1,717)	96
Net income (loss) attributable to WESCO International, Inc.	57,940	49,510	102,361	87,238
Comprehensive Income:
Foreign currency translation adjustment	(28,715)	33,381	(57,515)	44,949
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax				(252)
Comprehensive income attributable to WESCO International, Inc.	29,225	82,891	44,846	132,439
Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Revenues	921,075	843,518	1,803,474	1,622,129
Cost of goods sold	746,373	683,064	1,462,631	1,304,812
Selling, general and administrative expense	147,566	134,730	298,047	269,986
Depreciation and amortization	4,656	4,583	9,275	9,336
Income (Loss) from Subsidiaries, before Tax	51,122	40,753	96,325	75,181
Other Nonoperating Income (Expense)	(14,259)	(28,518)	(28,076)	(49,525)
Provision for income taxes	1,670	(1,862)	1,126	(2,898)
Net income (loss)	57,673	35,238	100,644	66,549
Less: Net (loss) income attributable to noncontrolling interest	0	0	0	0
Net income (loss) attributable to WESCO International, Inc.	57,673	35,238	100,644	66,549
Comprehensive Income:
Foreign currency translation adjustment	(28,715)	33,381	(57,515)	44,949
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax				(252)
Comprehensive income attributable to WESCO International, Inc.	28,958	68,619	43,129	111,750
Consolidation, Eliminations [Member]
Condensed Financial Information [Line Items]
Revenues	(39,450)	(34,555)	(78,044)	(60,229)
Cost of goods sold	(39,450)	(34,555)	(78,044)	(60,229)
Selling, general and administrative expense	0	0	0	0
Depreciation and amortization	0	0	0	0
Income (Loss) from Subsidiaries, before Tax	(108,795)	(90,288)	(196,969)	(162,515)
Other Nonoperating Income (Expense)	0	0	0	0
Provision for income taxes	0	0	0	0
Net income (loss)	(108,795)	(90,288)	(196,969)	(162,515)
Less: Net (loss) income attributable to noncontrolling interest	0	0	0	0
Net income (loss) attributable to WESCO International, Inc.	(108,795)	(90,288)	(196,969)	(162,515)
Comprehensive Income:
Foreign currency translation adjustment	57,430	(66,762)	115,030	(89,898)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax				504
Comprehensive income attributable to WESCO International, Inc.	(51,365)	(157,050)	(81,939)	(252,917)
Pension Plan [Member]
Condensed Financial Information [Line Items]
Other Nonoperating Gains (Losses)	$ (500)	$ (500)	$ (1,000)	$ (900)

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENT OF CASH FLOWS (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	$ (8,684)	$ 3,467
Net cash (used) provided by operating activities	86,821	66,769
Investing Activities:
Capital expenditures	(16,384)	(9,795)
Net cash used in investing activities	(25,068)	(6,328)
Financing Activities:
Proceeds from (Repayments of) Bank Overdrafts	(9,408)	155
Payments for Repurchase of Common Stock	(1,891)	(56,665)
Proceeds from (Payments for) Other Financing Activities	(550)	(768)
Net cash used in financing activities	(63,749)	(86,538)
Effect of exchange rate changes on cash and cash equivalents	(5,017)	3,765
Net change in cash and cash equivalents	(7,013)	(22,332)
Cash and cash equivalents at the beginning of period	117,953	110,131
Cash and cash equivalents at the end of period	110,940	87,799
Parent Company [Member]
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	0	0
Net cash (used) provided by operating activities	9,878	9,117
Investing Activities:
Capital expenditures	0	0
Proceeds from Dividends Received	0	0
Net cash used in investing activities	0	0
Financing Activities:
Borrowings	0	47,548
Repayments	(7,987)	0
Proceeds from (Repayments of) Bank Overdrafts	0	0
SEC Schedule, 12-04, Cash Dividends Paid to Registrant, Subsidiaries and Equity Method Investees	0	0
Payments for Repurchase of Common Stock	(1,891)
Proceeds from (Payments for) Other Financing Activities	0	0
Net cash used in financing activities	(9,878)	(9,117)
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	(37,524)	(72,761)
Net cash (used) provided by operating activities	31,192	73,130
Investing Activities:
Capital expenditures	(9,334)	(4,259)
Proceeds from Dividends Received	95,511	33,818
Net cash used in investing activities	48,653	(43,202)
Financing Activities:
Borrowings	191,888	313,749
Repayments	(260,888)	(348,478)
Proceeds from (Repayments of) Bank Overdrafts	0
SEC Schedule, 12-04, Cash Dividends Paid to Registrant, Subsidiaries and Equity Method Investees	0	0
Payments for Repurchase of Common Stock		0
Payments for Repurchase of Private Placement	0
Proceeds from (Payments for) Other Financing Activities	(9,958)	(613)
Net cash used in financing activities	(78,958)	(35,342)
Effect of exchange rate changes on cash and cash equivalents	0	0
Net change in cash and cash equivalents	887	(5,414)
Cash and cash equivalents at the beginning of period	50,602	41,552
Cash and cash equivalents at the end of period	51,489	36,138
Non-Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	(8,684)	12,322
Net cash (used) provided by operating activities	45,751	(15,478)
Investing Activities:
Capital expenditures	(7,050)	(5,536)
Proceeds from Dividends Received	0	0
Net cash used in investing activities	(15,734)	6,786
Financing Activities:
Borrowings	736,372	442,674
Repayments	(673,761)	(420,847)
Proceeds from (Repayments of) Bank Overdrafts	0	0
SEC Schedule, 12-04, Cash Dividends Paid to Registrant, Subsidiaries and Equity Method Investees	(95,511)	(33,818)
Payments for Repurchase of Common Stock	0	0
Proceeds from (Payments for) Other Financing Activities	0	0
Net cash used in financing activities	(32,900)	(11,991)
Effect of exchange rate changes on cash and cash equivalents	(5,017)	3,765
Net change in cash and cash equivalents	(7,900)	(16,918)
Cash and cash equivalents at the beginning of period	67,351	68,579
Cash and cash equivalents at the end of period	59,451	51,661
Consolidated Entities [Member]
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	(8,684)	3,467
Net cash (used) provided by operating activities	86,821	66,769
Investing Activities:
Capital expenditures	(16,384)	(9,795)
Proceeds from Dividends Received	0	0
Net cash used in investing activities	(25,068)	(6,328)
Financing Activities:
Borrowings	882,749	731,335
Repayments	(934,649)	(760,595)
Proceeds from (Repayments of) Bank Overdrafts	0	0
SEC Schedule, 12-04, Cash Dividends Paid to Registrant, Subsidiaries and Equity Method Investees	0	0
Payments for Repurchase of Common Stock	1,891	56,665
Proceeds from (Payments for) Other Financing Activities	(9,958)	(613)
Net cash used in financing activities	(63,749)	(86,538)
Effect of exchange rate changes on cash and cash equivalents	(5,017)	3,765
Net change in cash and cash equivalents	(7,013)	(22,332)
Cash and cash equivalents at the beginning of period	117,953	110,131
Cash and cash equivalents at the end of period	110,940	87,799
Consolidation, Eliminations [Member]
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	37,524	63,906
Net cash (used) provided by operating activities	0	0
Investing Activities:
Capital expenditures	0	0
Proceeds from Dividends Received	(95,511)	(33,818)
Net cash used in investing activities	(57,987)	30,088
Financing Activities:
Borrowings	(45,511)	(72,636)
Repayments	(7,987)	(8,730)
Proceeds from (Repayments of) Bank Overdrafts	0	0
SEC Schedule, 12-04, Cash Dividends Paid to Registrant, Subsidiaries and Equity Method Investees	(95,511)	(33,818)
Payments for Repurchase of Common Stock	0	0
Proceeds from (Payments for) Other Financing Activities	0	0
Net cash used in financing activities	57,987	(30,088)
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, 2018	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Goodwill	$ 1,744,694	$ 1,741,540	$ 1,771,877	$ 1,720,714
Goodwill, Foreign Currency Translation Gain (Loss)	$ (27,183)	$ 20,826

REVENUE (Details)

REVENUE (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Deferred Revenue	$ 11,600		$ 11,600		$ 15,500
Revenue from Contract with Customer, Excluding Assessed Tax	2,103,994	$ 1,909,624	4,097,909	$ 3,682,215
Cost of goods sold	1,704,100	1,543,510	3,318,066	2,966,083
Shipping and Handling [Member]
Disaggregation of Revenue [Line Items]
Cost of goods sold	$ 18,600	$ 14,400	$ 36,800	$ 27,800

REVENUE Deferred Revenue (Detai

REVENUE Deferred Revenue (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Revenue from Contract with Customer [Abstract]
Deferred Revenue	$ 11.6	$ 15.5

REVENUE Shipping and Handling C

REVENUE Shipping and Handling Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Cost of goods sold	$ 1,704,100	$ 1,543,510	$ 3,318,066	$ 2,966,083
Shipping and Handling [Member]
Cost of goods sold	$ 18,600	$ 14,400	$ 36,800	$ 27,800

REVENUE Variable Consideration

REVENUE Variable Consideration (Details)	6 Months Ended
	Jun. 30, 2018
Revenue from Contract with Customer [Abstract]
Revenue Recognition, Revenue Reductions [Policy Text Block]	WESCO’s revenues are adjusted for variable consideration, which includes customer volume rebates, returns, and discounts. WESCO measures variable consideration by estimating expected outcomes using analysis and inputs based upon anticipated performance, historical data, as well as current and forecasted information. Measurement and recognition of variable consideration is reviewed by management on a monthly basis and revenue is adjusted accordingly. Variable consideration reduced revenue for the three months ended June 30, 2018 and 2017 by approximately $25.0 million and $21.7 million , respectively, and by approximately $49.4 million and $42.3 million for the six months ended June 30, 2018 and 2017 , respectively.

REVENUE Revenue, Performance Ob

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

NET INTEREST AND OTHER (Details

NET INTEREST AND OTHER (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018
Other Income and Expenses [Abstract]
Foreign Currency Transaction Gain (Loss), before Tax	$ 0.4	$ 2.6