WESCO International (WCC) 10-Q 3 Nov 17 2017 Q3 Quarterly report Financial data

DOCUMENT AND ENTITY INFORMATION

DOCUMENT AND ENTITY INFORMATION Document - shares	9 Months Ended
	Sep. 30, 2017	Nov. 02, 2017
Entity [Abstract]
Entity Registrant Name	WESCO INTERNATIONAL INC.
Entity Central Index Key	929,008
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		47,002,338

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017USD ($)	Sep. 30, 2017USD ($)	Dec. 31, 2016USD ($)
Depreciation, Depletion and Amortization, Nonproduction	$ 16,074	$ 47,758
Other Accrued Liabilities, Current	87,143	87,143
Current Assets:
Cash and cash equivalents	94,083	94,083	$ 110,131
Allowance for Doubtful Accounts Receivable, Current	24,240	24,240	22,007
Trade accounts receivable, net of allowance for doubtful accounts of $23,069 and $19,309 in 2014 and 2013, respectively	1,236,612	1,236,612	1,034,402
Accounts and Other Receivables, Net, Current	82,588	82,588	85,019
Inventories, net	925,049	925,049	821,441
Prepaid expenses and other current assets	71,795	71,795
Total current assets	2,410,127	2,410,127	2,103,078
Property, buildings and equipment, net of accumulated depreciation of $229,041 and $213,758 in 2014 and 2013, respectively	157,591	157,591	157,607
Intangible assets, net	378,153	378,153	393,362
Goodwill	1,776,918	1,776,918	1,730,950
Other assets	41,679	41,679	46,844
Total assets	4,764,468	4,764,468	4,431,841
Current Liabilities:
Accounts payable	838,427	838,427	684,721
Accrued payroll and benefit costs	50,848	50,848	49,250
Short-term debt	39,712	39,712	20,920
Current portion of long-term debt	1,213	1,213	1,218
Total current liabilities	1,043,493	1,043,493	873,799
Long-term Debt, Excluding Current Maturities	1,368,301	1,368,301	1,363,135
Other noncurrent liabilities	65,811	65,811	63,031
Deferred Tax Liabilities, Net, Noncurrent	179,630	179,630
Total liabilities	2,657,235	2,657,235	2,468,210
Commitments and Contingencies
Bank Overdrafts	26,150	26,150	29,384
Stockholders' Equity:
Preferred stock, $.01 par value; 20,000,000 shares authorized, no shares issued or outstanding	0	0	0
Additional capital	995,670	995,670	986,020
Retained earnings	2,056,961	2,056,961
Treasury stock, at cost; 18,247,467 and 18,179,275 shares in 2014 and 2013, respectively	(647,138)	(647,138)	(542,537)
Accumulated other comprehensive income	(295,622)	(295,622)
Total WESCO International stockholders' equity	2,107,233	2,107,233	1,963,631
Noncontrolling interest	(3,271)	(3,271)	(3,269)
Total stockholders' equity	2,110,504	2,110,504	1,966,900
Total liabilities and stockholders' equity	4,764,468	4,764,468	4,431,841
Common Stock [Member]
Stockholders' Equity:
Common stock	590	590	588
Common Class B [Member]
Stockholders' Equity:
Common stock	$ 43	$ 43	$ 43

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parentheticals) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Allowance for doubtful accounts	$ 24,240,000	$ 22,007,000
Accumulated depreciation	274,643,000	259,126,000
Finite-Lived Intangible Assets, Accumulated Amortization	214,225	178,813
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ 14,302,000	$ 17,278,000
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	20,000,000	20,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Treasury stock, shares (in shares)	16,375,816	14,545,715
Common Stock [Member]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	210,000,000	210,000,000
Common stock, shares, issued (in shares)	59,036,037	58,817,781
Common stock, shares outstanding (in shares)	46,999,652	48,611,497
Common Class B [Member]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	20,000,000	20,000,000
Common stock, shares, issued (in shares)	4,339,431	4,339,431
Common stock, shares outstanding (in shares)	0	0

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Net sales	$ 2,000,159	$ 1,855,212	$ 5,682,375	$ 5,542,755
Cost of goods sold	1,614,814	1,490,173	4,580,896	4,443,079
Selling, general and administrative expense	280,021	255,547	814,275	799,356
Depreciation and amortization	16,074	16,937	47,758	50,269
Income from operations	89,250	92,555	239,446	250,051
Interest expense, net	17,311	20,792	50,847	59,073
Gain (Loss) on Extinguishment of Debt	0	123,933	0	123,933
Income before income taxes	71,939	(52,170)	188,599	67,045
Provision for income taxes	18,363	(21,149)	47,684	13,678
Net income	53,576	(31,021)	140,915	53,367
Net (loss) income attributable to noncontrolling interest	(99)	590	(3)	(876)
Net income attributable to WESCO International, Inc.	53,675	(31,611)	140,918	54,243
Comprehensive Income:
Foreign currency translation adjustment	51,148	(13,993)	96,097	66,512
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	0	0	252	(16)
Comprehensive income attributable to WESCO International, Inc.	$ 104,823	$ (45,604)	$ 237,267	$ 120,739
Earnings per share attributable to WESCO International, Inc.
Basic (in dollars per share)	$ 1.13	$ (0.73)	$ 2.93	$ 1.27
Diluted (in dollars per share)	$ 1.12	$ (0.73)	$ 2.90	$ 1.13

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Operating Activities:
Net income	$ 140,915	$ 53,367
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	47,758	50,269
Deferred income taxes	8,433	(21,842)
Gain (Loss) on Extinguishment of Debt	0	123,933
Other operating activities, net	12,617	11,228
Changes in assets and liabilities
Increase (Decrease) in Accounts Receivable	174,667	3,075
Increase (Decrease) in Accounts and Other Receivables	(4,421)	(15,524)
Inventories, net	(86,736)	(7,651)
Prepaid expenses and other current assets	(8,515)	(8,625)
Accounts payable	138,348	(30,289)
Accrued payroll and benefit costs	2,383	(2,648)
Other current and noncurrent liabilities	(3,846)	36,997
Net cash provided by operating activities	81,111	217,188
Investing Activities:
Capital expenditures	(15,970)	(13,183)
Acquisition payments, net of cash acquired	0	(50,745)
Other investing activities	3,490	(3,885)
Net cash used in investing activities	(12,480)	(67,813)
Financing Activities:
Proceeds from issuance of short-term debt	130,890	89,847
Repayments of short-term debt	(114,972)	(96,535)
Proceeds from issuance of long-term debt	1,079,718	1,731,715
Repayments of Long-term Debt	(1,076,718)	(1,915,545)
Other financing activities, net	(4,380)	(3,494)
Net cash used in financing activities	(92,164)	(198,085)
Payments for Repurchase of Common Stock	(106,702)	(4,073)
Effect of exchange rate on cash and cash equivalents	7,485	1,268
Net change in cash and cash equivalents	(16,048)	(47,442)
Cash and cash equivalents at the beginning of period	110,131	160,279
Cash and cash equivalents at the end of period	$ 94,083	$ 112,837

ORGANIZATION

ORGANIZATION	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
ORGANIZATION	1. ORGANIZATION WESCO International, Inc. ("WESCO International") and its subsidiaries (collectively, “WESCO” or the "Company"), headquartered in Pittsburgh, Pennsylvania, is a full-line distributor of electrical, industrial and communications maintenance, repair and operating (MRO) and original equipment manufacturer (OEM) products, construction materials, and advanced supply chain management and logistics services used primarily in the industrial, construction, utility and commercial, institutional and government markets. WESCO serves approximately 75,000 active customers globally, through approximately 500 full service branches and ten distribution centers located primarily in the United States, Canada and Mexico, with operations in 14 additional countries.

ACCOUNTING POLICIES

ACCOUNTING POLICIES	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
ACCOUNTING POLICIES	2. ACCOUNTING POLICIES Basis of Presentation The accompanying unaudited Condensed Consolidated Financial Statements of WESCO have been prepared in accordance with Rule 10-01 of Regulation S-X of the Securities and Exchange Commission (the “SEC”). The unaudited condensed consolidated financial information should be read in conjunction with the audited Consolidated Financial Statements and Notes thereto included in WESCO’s 2016 Annual Report on Form 10-K as filed with the SEC on February 22, 2017. The Condensed Consolidated Balance Sheet at December 31, 2016 was derived from the audited Consolidated Financial Statements as of that date, but does not include all of the disclosures required by accounting principles generally accepted in the United States of America. The unaudited Condensed Consolidated Balance Sheet as of September 30, 2017 , the unaudited Condensed Consolidated Statements of Income and Comprehensive Income for the three and nine months ended September 30, 2017 and 2016 , respectively, and the unaudited Condensed Consolidated Statements of Cash Flows for the nine months ended September 30, 2017 and 2016 , respectively, in the opinion of management, have been prepared on the same basis as the audited Consolidated Financial Statements and include all adjustments necessary for the fair statement of the results of the interim periods presented herein. All adjustments reflected in the unaudited condensed consolidated financial information are of a normal recurring nature unless indicated. The results for the interim periods presented herein are not necessarily indicative of the results to be expected for the full year. Revision of Prior Period Financial Statements In the third quarter of 2017, management determined that the Company's income taxes receivable and payable and other tax account balances were overstated as of December 31, 2016 by a cumulative net amount of $46.4 million , which related to multiple prior periods. The Company also identified a $10.2 million understatement related to deferred income taxes and goodwill. In accordance with Staff Accounting Bulletin (“SAB”) No. 99, Materiality , and SAB No. 108, Considering the Effects of Prior Year Misstatements when Quantifying Misstatements in Current Year Financial Statements , management concluded that these misstatements are not material to the Company's previously issued annual and interim financial statements. Correcting the effected financial statement line items in the quarterly period ended September 30, 2017 would materially misstate the condensed consolidated financial information presented herein. Accordingly, the Condensed Consolidated Balance Sheet at December 31, 2016 in this Quarterly Report on Form 10-Q has been revised. There was an immaterial effect on the Condensed Consolidated Statements of Income and Comprehensive Income for the three and nine months ended September 30, 2016 , and no effect on the Condensed Consolidated Statements of Cash Flows for the respective periods presented herein. Periods not presented herein will be revised, as applicable, in future filings. The following table presents the effects on the financial statement line items that were revised: December 31, 2016 As Reported Adjustment As Revised (In thousands) Prepaid expenses and other current assets $ 121,464 $ (69,379 ) $ 52,085 Total current assets 2,172,457 (69,379 ) 2,103,078 Goodwill 1,720,714 10,236 1,730,950 Total assets 4,490,984 (59,143 ) 4,431,841 Other current liabilities 111,304 (22,998 ) 88,306 Total current liabilities 896,797 (22,998 ) 873,799 Deferred income taxes 158,009 10,236 168,245 Total liabilities 2,480,972 (12,762 ) 2,468,210 Retained earnings 1,956,532 (41,775 ) 1,914,757 Accumulated other comprehensive loss (387,365 ) (4,606 ) (391,971 ) Total stockholders' equity 2,010,012 (46,381 ) 1,963,631 Total liabilities and stockholders' equity 4,490,984 (59,143 ) 4,431,841 Recently Adopted Accounting Pronouncements In March 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2016-09, Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting , which simplifies several aspects of accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. The amendments in this ASU affect all entities that issue share-based payment awards to their employees. The Company adopted this ASU in the first quarter of 2017. The amendment related to the recognition of excess tax benefits and deficiencies was applied prospectively and, as disclosed in Note 9, lowered the Company's effective tax rate for the nine months ended September 30, 2017 . The amendment related to the presentation of excess tax benefits on the statement of cash flows was also applied prospectively, and did not have a material impact on WESCO's cash flows. The other amendments, which were adopted by the Company according to the respective transition requirements, had no impact on the consolidated financial statements and notes thereto. In October 2016, the FASB issued ASU 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory. The purpose of ASU 2016-16 is to simplify the income tax accounting of an intra-entity transfer of an asset other than inventory and to record its effect when the transfer occurs. The Company early adopted this ASU on a modified retrospective basis in the first quarter of 2017. The adoption of this ASU did not have a material impact on WESCO's financial position and it had no impact on its results of operations or cash flows. Recently Issued Accounting Pronouncements In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers: Deferral of Effective Date . The Company previously reported that in May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers , which provides a framework for addressing revenue recognition issues and replaces almost all existing revenue recognition guidance in current U.S. generally accepted accounting principles. The core principle of ASU 2014-09 is for companies to recognize revenue for the transfer of goods or services to customers in amounts that reflect the consideration to which the company expects to be entitled in exchange for those goods or services. ASU 2014-09 will also result in enhanced disclosures about revenue, provide guidance for transactions that were not previously addressed comprehensively, and improve guidance for multiple-element arrangements. The amendments in ASU 2015-14 defer the effective date of the new revenue recognition guidance to annual reporting periods beginning after December 15, 2017, including interim periods within that reporting period. During 2016, the FASB issued four ASUs that address implementation issues and correct or improve certain aspects of the new revenue recognition guidance, including ASU 2016-08, Principal versus Agent Considerations (Reporting Revenue Gross versus Net) , ASU 2016-10, Identifying Performance Obligations and Licensing , ASU 2016-12, Narrow-Scope Improvements and Practical Expedients and ASU 2016-20, Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers . These ASUs do not change the core principles in the revenue recognition standard outlined above. The Company has developed a multiphase plan and established a cross-functional team to evaluate and implement the new standard. Management has completed the diagnostic phase, which involved reviewing various customer contracts and comparing current accounting to the requirements of the new standard. Currently management is evaluating the new disclosure requirements and identifying and implementing appropriate changes to its business processes and controls to support recognition and disclosure under the new standard. The new standard will be adopted in the first quarter of 2018 and the Company expects to use the modified retrospective approach. Management will continue to evaluate the impact that this pronouncement may have on WESCO's consolidated financial statements and notes thereto. In February 2016, the FASB issued ASU 2016-02, Leases , a comprehensive new standard that amends various aspects of existing accounting guidance for leases, including the recognition of a right-of-use asset and a lease liability on the balance sheet and disclosing key information about leasing arrangements. This guidance is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Early adoption is permitted. The new leasing standard requires modified retrospective transition, which requires application of the new guidance at the beginning of the earliest comparative period presented in the year of adoption. Management is currently evaluating the impact of this new standard on WESCO's consolidated financial statements and notes thereto. In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , which introduces new guidance for the accounting for credit losses on certain financial instruments. The amendments in ASU 2016-13 are effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years and early adoption is permitted. Management is currently evaluating the impact of this accounting standard on WESCO's consolidated financial statements and notes thereto. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (a consensus of the Emerging Issues Task Force) . This ASU provides guidance on eight specific cash flow issues where there is diversity in practice. The amendments in this ASU are effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted, including adoption in an interim period. Management is currently evaluating the impact of this accounting standard on WESCO's consolidated financial statements and notes thereto. In January 2017, the FASB issued ASU 2017-04, Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment, which eliminates Step 2 from the goodwill impairment test. Under the amendments in this update, an entity should perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. An entity should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. An entity should apply the amendments in this ASU on a prospective basis. This guidance is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Management has not yet evaluated the impact of this accounting standard on WESCO's consolidated financial statements and notes thereto. In March 2017, the FASB issued ASU 2017-07, Compensation—Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost . Presently, net benefit cost is reported as an employee cost within operating income (or capitalized into assets when appropriate). This amendment requires the bifurcation of net benefit cost. The service component will be presented with other employee compensation costs in operating income (or capitalized in assets). The other components will be reported separately outside of operations, and will not be eligible for capitalization. This guidance is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Early adoption is permitted. Management has not yet evaluated the impact of this accounting standard on WESCO's consolidated financial statements and notes thereto. In May 2017, the FASB issued ASU 2017-09, Compensation—Stock Compensation (Topic 718): Scope of Modification Accounting , which clarifies when to account for a change to the terms or conditions of a share-based payment award as a modification. Under the new guidance, modification accounting is required only if the fair value, the vesting conditions, or the classification of the award (as equity or liability) changes as a result of the change in terms or conditions. The guidance is effective prospectively for all companies for annual periods beginning on or after December 15, 2017. Early adoption is permitted. Management has not yet evaluated the impact of this accounting standard on WESCO's consolidated financial statements and notes thereto. Other pronouncements issued by the FASB or other authoritative accounting standards groups with future effective dates are either not applicable or are not expected to be significant to WESCO’s financial position, results of operations or cash flows. Fair Value of Financial Instruments The Company’s financial instruments consist of cash and cash equivalents, accounts receivable, accounts payable and other accrued liabilities, and outstanding indebtedness. The reported carrying amounts of WESCO’s financial instruments approximate their fair values. The Company uses a market approach to fair value all of its debt instruments, utilizing quoted prices in active markets, interest rates and other relevant information generated by market transactions involving similar instruments. Therefore, all of the Company's debt instruments are classified as Level 2 within the valuation hierarchy.

ACQUISITIONS

ACQUISITIONS	9 Months Ended
	Sep. 30, 2017
Business Combinations [Abstract]
ACQUISITIONS	3. ACQUISITIONS On March 14, 2016 , WESCO Distribution, Inc. ("WESCO Distribution") completed the acquisition of Atlanta Electrical Distributors, LLC ("AED"), an Atlanta-based electrical distributor focused on the construction and MRO markets from five locations in Georgia with approximately $85 million in annual sales. WESCO Distribution funded the purchase price paid at closing with borrowings under its revolving credit facility. The purchase price was allocated to the respective assets and liabilities based upon their estimated fair values as of the acquisition date. In addition to the cash paid at closing, the purchase price included a contingent payment that may be earned upon the achievement of certain financial performance targets over three consecutive one year periods. The fair value of the contingent consideration was determined using a probability-weighted outcome analysis and Level 3 inputs such as internal forecasts. This amount was accrued at the maximum potential payout under the terms of the purchase agreement. The fair value of intangibles was estimated by management and the allocation resulted in intangible assets of $21.8 million and goodwill of $30.0 million . The intangible assets include customer relationships of $15.8 million amortized over 13 and 14 years, a trademark of $6.0 million amortized over 13 years, and non-compete agreements of less than $0.1 million amortized over 5 years. No residual value was estimated for the intangible assets being amortized. The majority of goodwill is deductible for tax purposes.

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	9 Months Ended
	Sep. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
STOCK-BASED COMPENSATION	5. STOCK-BASED COMPENSATION WESCO’s stock-based employee compensation plans are comprised of stock-settled stock appreciation rights, restricted stock units and performance-based awards. Compensation cost for all stock-based awards is measured at fair value on the date of grant and compensation cost is recognized, net of estimated forfeitures, over the service period for awards expected to vest. The fair value of stock-settled stock appreciation rights and performance-based awards with market conditions is determined using the Black-Scholes and Monte Carlo simulation models, respectively. The fair value of restricted stock units and performance-based awards with performance conditions is determined by the grant-date closing price of WESCO’s common stock. The forfeiture assumption is based on WESCO’s historical employee behavior that is reviewed on an annual basis. No dividends are assumed. During the three and nine months ended September 30, 2017 and 2016 , WESCO granted the following stock-settled stock appreciation rights, restricted stock units and performance-based awards at the following weighted-average fair values: Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, Stock-settled stock appreciation rights granted 12,076 1,745 455,807 709,999 Weighted-average fair value $ 15.74 $ 16.68 $ 20.52 $ 12.91 Restricted stock units granted 2,313 — 100,993 143,305 Weighted-average fair value $ 57.30 $ — $ 71.33 $ 42.45 Performance-based awards granted — — 39,978 91,768 Weighted-average fair value $ — $ — $ 76.63 $ 47.00 The fair value of stock-settled stock appreciation rights was estimated using the following weighted-average assumptions: Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, Risk free interest rate 1.8 % 1.3 % 1.9 % 1.2 % Expected life (in years) 5 5 5 5 Expected volatility 28 % 31 % 29 % 32 % The risk-free interest rate is based on the U.S. Treasury Daily Yield Curve rate as of the grant date. The expected life is based on historical exercise experience and the expected volatility is based on the volatility of the Company's daily stock prices over a five-year period preceding the grant date. The following table sets forth a summary of stock-settled stock appreciation rights and related information for the nine months ended September 30, 2017 : Awards Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (In years) Aggregate Intrinsic Value (In thousands) Outstanding at December 31, 2016 2,439,487 $ 52.62 Granted 455,807 71.21 Exercised (472,873 ) 42.41 Forfeited (143,506 ) 66.21 Outstanding at September 30, 2017 2,278,915 57.60 6.4 $ 18,344 Exercisable at September 30, 2017 1,359,744 $ 56.71 4.8 $ 12,212 The following table sets forth a summary of time-based restricted stock units and related information for the nine months ended September 30, 2017 : Awards Weighted- Average Fair Value Unvested at December 31, 2016 257,096 $ 57.47 Granted 100,993 71.33 Vested (43,780 ) 85.13 Forfeited (18,022 ) 55.96 Unvested at September 30, 2017 296,287 $ 58.20 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 nine months ended September 30, 2017 : Awards Weighted- Average Fair Value Unvested at December 31, 2016 149,320 $ 60.36 Granted 39,978 76.63 Vested — — Forfeited (39,650 ) 77.40 Unvested at September 30, 2017 149,648 $ 60.19 The fair value of the performance shares granted during the nine months ended September 30, 2017 and 2016 was estimated using the following weighted-average assumptions: Nine Months Ended September 30, September 30, Grant date share price $ 71.65 $ 42.44 WESCO expected volatility 29 % 26 % Peer group median volatility 24 % 24 % Risk-free interest rate 1.5 % 0.9 % Correlation of peer company returns 114 % 122 % The unvested performance-based awards in the table above include 74,824 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 74,824 shares of performance-based awards in the table above is dependent upon the three-year average growth rate of WESCO's net income. These awards are accounted for as awards with performance conditions; compensation cost is recognized over the performance period based upon WESCO's determination of whether it is probable that the performance targets will be achieved. WESCO recognized $3.5 million and $3.4 million of non-cash stock-based compensation expense, which is included in selling, general and administrative expenses, for the three months ended September 30, 2017 and 2016 , respectively. WESCO recognized $11.3 million and $10.4 million of non-cash stock-based compensation expense, which is included in selling, general and administrative expenses, for the nine months ended September 30, 2017 and 2016 , respectively. As of September 30, 2017 , there was $22.6 million of total unrecognized compensation cost related to non-vested stock-based compensation arrangements for all awards previously made, of which approximately $3.7 million is expected to be recognized over the remainder of 2017 , $11.4 million in 2018 , $6.7 million in 2019 and $0.8 million in 2020 .

EARNINGS PER SHARE

EARNINGS PER SHARE	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
EARNINGS PER SHARE	6. EARNINGS PER SHARE Basic earnings per share is computed by dividing net income attributable to WESCO International by the weighted-average number of common shares outstanding during the periods. Diluted earnings per share is computed by dividing net income attributable to WESCO International by the weighted-average common shares and common share equivalents outstanding during the periods. The dilutive effect of common share equivalents is considered in the diluted earnings per share computation using the treasury stock method, which includes consideration of equity awards and contingently convertible debt. The following table sets forth the details of basic and diluted earnings per share: Three Months Ended Nine Months Ended September 30, September 30, (In thousands, except per share data) 2017 2016 2017 2016 Net income (loss) attributable to WESCO International, Inc. $ 53,675 $ (31,611 ) $ 140,918 $ 54,243 Weighted-average common shares outstanding used in computing basic earnings per share 47,415 43,378 48,134 42,611 Common shares issuable upon exercise of dilutive equity awards 389 511 508 519 Common shares issuable from contingently convertible debentures (see below for basis of calculation) — 4,851 — 4,908 Weighted-average common shares outstanding and common share equivalents, diluted 47,804 48,740 48,642 48,038 Weighted-average common shares outstanding and common share equivalents used in computing diluted earnings per share 47,804 43,378 48,642 48,038 Earnings (loss) per share attributable to WESCO International, Inc. Basic $ 1.13 $ (0.73 ) $ 2.93 $ 1.27 Diluted $ 1.12 $ (0.73 ) $ 2.90 $ 1.13 For the three and nine months ended September 30, 2017 , the computation of diluted earnings per share attributable to WESCO International, Inc. excluded stock-based awards of approximately 1.5 million and 1.3 million , respectively. For the three and nine months ended September 30, 2016 , the computation of diluted (loss) earnings per share attributable to WESCO International, Inc. excluded stock-based awards of approximately 1.3 million . These amounts were excluded because their effect would have been antidilutive. Because of WESCO’s previous obligation to settle the par value of the 6.0% Convertible Senior Debentures due 2029 (the "2029 Debentures") in cash upon conversion, WESCO was required to include shares underlying the 2029 Debentures in its diluted weighted-average shares outstanding when the average stock price per share for the period exceeded the conversion price of the debentures. Only the number of shares that would have been issuable under the treasury stock method of accounting for share dilution were included, which was based upon the amount by which the average stock price exceeded the conversion price. The conversion price of the 2029 Debentures was $28.87 and the maximum amount of share dilution was limited to 11,951,932 shares. Since the 2029 Debentures were redeemed on September 15, 2016 , there was no dilution from contingently convertible debentures for the three and nine months ended September 30, 2017 . As a result of the net loss attributable to WESCO International, Inc. for the three months ended September 30, 2016 , dilutive shares were not included in the calculation of diluted loss per share because their effect was antidilutive. For the nine months ended September 30, 2016 , the effect of the 2029 Debentures on diluted earnings per share attributable to WESCO International, Inc. was a decrease of $0.13 . In December 2014, the Company's Board of Directors authorized the repurchase of up to $300 million of the Company's common stock through December 31, 2017 . As of December 31, 2016 , WESCO had repurchased 2,468,576 shares of the Company's common stock for $150.0 million under this repurchase authorization. During the three months ended June 30, 2017 , the Company repurchased 804,291 shares under the repurchase authorization for $50.0 million . On August 7, 2017, the Company entered into an accelerated stock repurchase agreement (the "ASR Transaction") with a financial institution to repurchase additional shares of its common stock. In exchange for an up-front cash payment of $50.0 million , the Company received 974,246 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 borrowings under the Company's revolving credit facility and accounts receivable securitization facility. For purposes of computing earnings per share, share repurchases have been reflected as a reduction to common shares outstanding on the respective delivery dates.

EMPLOYEE BENEFIT PLANS

EMPLOYEE BENEFIT PLANS	9 Months Ended
	Sep. 30, 2017
Retirement Benefits [Abstract]
EMPLOYEE BENEFIT PLANS	7. EMPLOYEE BENEFIT PLANS A majority of WESCO’s employees are covered by defined contribution retirement savings plans for their services rendered subsequent to WESCO’s formation. WESCO also offers a deferred compensation plan for select individuals. For U.S. participants, WESCO matches contributions made by employees at an amount equal to 50% of participants' total monthly contributions up to a maximum of 6% of eligible compensation. For Canadian participants, WESCO makes contributions in amounts ranging from 3% to 5% of the participants' eligible compensation based on years of continuous service. WESCO may also make, subject to the Board of Directors' approval, a discretionary contribution to the defined contribution retirement savings plan covering U.S. participants if certain predetermined profit levels are attained. For the nine months ended September 30, 2017 and 2016 , WESCO incurred charges of $20.3 million and $18.1 million , respectively, for all such plans. Contributions are made in cash to employee retirement savings plan accounts. The deferred compensation plan is an unfunded plan. As of September 30, 2017 and December 31, 2016 , the Company's obligation under the deferred compensation plan was $23.4 million and $21.7 million , respectively. Employees have the option to transfer balances allocated to their accounts in the defined contribution retirement savings plan and the deferred compensation plan into any of the available investment options. In connection with the December 14, 2012 acquisition of EECOL, the Company assumed a contributory defined benefit plan covering substantially all Canadian employees of EECOL and a Supplemental Executive Retirement Plan for certain executives of EECOL. The following table reflects the components of net periodic benefit costs for the defined benefit plans: Three Months Ended Nine Months Ended September 30, September 30, (In thousands of dollars) 2017 2016 2017 2016 Service cost $ 1,118 $ 977 $ 3,234 $ 2,889 Interest cost 1,007 979 2,915 2,898 Expected return on plan assets (1,432 ) (1,353 ) (4,144 ) (4,004 ) Recognized actuarial gain (51 ) (10 ) (149 ) (31 ) Net periodic benefit cost $ 642 $ 593 $ 1,856 $ 1,752 During the three and nine months ended September 30, 2017 , there were no employer contributions to the defined benefit plans. During the three and nine months ended September 30, 2016 , the Company made aggregate cash contributions of $0.5 million and $1.4 million , respectively, to the defined benefit plans.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	9 Months Ended
	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	8. COMMITMENTS AND CONTINGENCIES WESCO is subject to the laws and regulations of states and other jurisdictions concerning the identification, reporting and escheatment (the transfer of property to the state) of unclaimed or abandoned funds, and is subject to audit and examination for compliance with these requirements. WESCO Distribution is undergoing a compliance audit in the State of Delaware concerning the identification, reporting and escheatment of unclaimed or abandoned property. The third party auditor conducting the audit on behalf of the State has completed the audit fieldwork and provided a draft of its preliminary findings to the Company and the State for review. A final report is expected to be issued at some point in the future. The Company has been working with an outside consultant during the audit process and in discussions with the auditors. The Company is defending the audit, the outcome of which cannot be predicted with certainty at this time, and is evaluating its alternatives under applicable laws and regulations. If the Company and State do not reach resolution after further discussion, the State may issue a demand for payment, which the Company may either agree to pay or appeal, in full or in part. The Company has recorded a liability for unclaimed property based on the facts currently known to the Company. In October 2014, WESCO was notified that the New York County District Attorney’s Office is conducting a criminal investigation involving minority and disadvantaged business contracting practices in the construction industry in New York City and that various contractors, minority and disadvantaged business firms, and their material suppliers, including the Company, are a part of this investigation. The Company is cooperating with the government investigation. The Company cannot predict the outcome or impact of the matter at this time, but could be subject to fines, penalties or other adverse consequences. The Company has recorded a liability for the matter based on the facts currently known to the Company.

INCOME TAXES

INCOME TAXES	9 Months Ended
	Sep. 30, 2017
Income Tax Disclosure [Abstract]
INCOME TAXES	9. INCOME TAXES The effective tax rate for the three and nine months ended September 30, 2017 was 25.5% and 25.3% , respectively. The effective tax rate for the three and nine months ended September 30, 2016 was 40.5% and 20.4% , respectively. The effective tax rates for the three and nine months ended September 30, 2016 were impacted by the redemption of the 2029 Debentures on September 15, 2016 . WESCO’s effective tax rate is typically lower than the federal statutory rate of 35% due to benefits resulting from the tax effect of intercompany financing and lower tax rates on foreign earnings, which are partially offset by nondeductible expenses and state taxes. The current year's effective tax rate is impacted by favorable discrete items, including a benefit from the exercise and vesting of stock-based awards, as well as the mix of income earned in jurisdictions with lower tax rates. The total amount of unrecognized tax benefits was reduced by $1.6 million during the nine months ended September 30, 2017 to $4.6 million due to the expiration of statutes of limitation and the settlement of state audits. At September 30, 2017 , the amount of unrecognized tax benefits that could affect the effective tax rate if recognized in the consolidated financial statements was $6.0 million . Within the next twelve months, it is reasonably possible that the amount of unrecognized tax benefits will decrease by approximately $0.2 million due to the expiration of statutes of limitation and the settlement of state audits. Of this amount, $0.2 million could impact the effective tax rate.

OTHER FINANCIAL INFORMATION

OTHER FINANCIAL INFORMATION	9 Months Ended
	Sep. 30, 2017
Condensed Financial Information [Abstract]
OTHER FINANCIAL INFORMATION	10. CONDENSED CONSOLIDATING FINANCIAL INFORMATION WESCO Distribution has outstanding $500 million in aggregate principal amount of 5.375% Senior Notes due 2021 (the "2021 Notes") and $350 million in aggregate principal amount of 5.375% Senior Notes due 2024 (the "2024 Notes"). The 2021 Notes and 2024 Notes are unsecured senior obligations of WESCO Distribution and are fully and unconditionally guaranteed on a senior unsecured basis by WESCO International. Condensed consolidating financial information for WESCO International, WESCO Distribution and the non-guarantor subsidiaries is presented in the following tables. Condensed Consolidating Balance Sheet September 30, 2017 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Cash and cash equivalents $ — $ 45,775 $ 48,308 $ — $ 94,083 Trade accounts receivable, net — — 1,236,612 — 1,236,612 Inventories — 403,752 521,297 — 925,049 Prepaid expenses and other current assets 13,642 42,130 203,991 (105,380 ) 154,383 Total current assets 13,642 491,657 2,010,208 (105,380 ) 2,410,127 Intercompany receivables, net — — 2,141,945 (2,141,945 ) — Property, buildings and equipment, net — 50,191 107,400 — 157,591 Intangible assets, net — 2,932 375,221 — 378,153 Goodwill — 257,623 1,519,295 — 1,776,918 Investments in affiliates 3,817,521 4,228,307 — (8,045,828 ) — Other assets — 18,615 23,064 — 41,679 Total assets $ 3,831,163 $ 5,049,325 $ 6,177,133 $ (10,293,153 ) $ 4,764,468 Accounts payable $ — $ 443,675 $ 394,752 $ — $ 838,427 Short-term debt — — 39,712 — 39,712 Other current liabilities — 117,701 153,033 (105,380 ) 165,354 Total current liabilities — 561,376 587,497 (105,380 ) 1,043,493 Intercompany payables, net 1,707,926 434,019 — (2,141,945 ) — Long-term debt, net — 968,361 399,940 — 1,368,301 Other noncurrent liabilities 12,733 61,635 171,073 — 245,441 Total WESCO International, Inc. stockholders' equity 2,110,504 3,023,934 5,021,894 (8,045,828 ) 2,110,504 Noncontrolling interests — — (3,271 ) — (3,271 ) Total liabilities and stockholders’ equity $ 3,831,163 $ 5,049,325 $ 6,177,133 $ (10,293,153 ) $ 4,764,468 Condensed Consolidating Balance Sheet December 31, 2016 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Cash and cash equivalents $ — $ 41,552 $ 68,579 $ — $ 110,131 Trade accounts receivable, net — — 1,034,402 — 1,034,402 Inventories — 364,562 456,879 — 821,441 Prepaid expenses and other current assets 13,647 34,833 211,637 (123,013 ) 137,104 Total current assets 13,647 440,947 1,771,497 (123,013 ) 2,103,078 Intercompany receivables, net — — 2,060,336 (2,060,336 ) — Property, buildings and equipment, net — 51,824 105,783 — 157,607 Intangible assets, net — 3,417 389,945 — 393,362 Goodwill — 257,623 1,473,327 — 1,730,950 Investments in affiliates 3,538,476 4,028,502 — (7,566,978 ) — Other assets — 23,846 22,998 — 46,844 Total assets $ 3,552,123 $ 4,806,159 $ 5,823,886 $ (9,750,327 ) $ 4,431,841 Accounts payable $ — $ 381,795 $ 302,926 $ — $ 684,721 Short-term debt — — 20,920 — 20,920 Other current liabilities — 120,299 170,872 (123,013 ) 168,158 Total current liabilities — 502,094 494,718 (123,013 ) 873,799 Intercompany payables, net 1,572,486 487,850 — (2,060,336 ) — Long-term debt, net — 983,449 379,686 — 1,363,135 Other noncurrent liabilities 12,737 55,898 162,641 — 231,276 Total WESCO International, Inc. stockholders' equity 1,966,900 2,776,868 4,790,110 (7,566,978 ) 1,966,900 Noncontrolling interests — — (3,269 ) — (3,269 ) Total liabilities and stockholders’ equity $ 3,552,123 $ 4,806,159 $ 5,823,886 $ (9,750,327 ) $ 4,431,841 Condensed Consolidating Statement of Income and Comprehensive Income Three Months Ended September 30, 2017 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 867,973 $ 1,169,377 $ (37,191 ) $ 2,000,159 Cost of goods sold (excluding depreciation and amortization) — 697,896 954,109 (37,191 ) 1,614,814 Selling, general and administrative expenses — 140,638 139,383 — 280,021 Depreciation and amortization — 4,475 11,599 — 16,074 Results of affiliates’ operations 53,576 42,726 — (96,302 ) — Interest expense (income), net — 25,436 (8,125 ) — 17,311 Income tax (benefit) expense — (136 ) 18,499 — 18,363 Net income 53,576 42,390 53,912 (96,302 ) 53,576 Net income attributable to noncontrolling interests — — (99 ) — (99 ) Net income attributable to WESCO International, Inc. $ 53,576 $ 42,390 $ 54,011 $ (96,302 ) $ 53,675 Other comprehensive income: Foreign currency translation adjustments 51,148 51,148 51,148 (102,296 ) 51,148 Comprehensive income attributable to WESCO International, Inc. $ 104,724 $ 93,538 $ 105,159 $ (198,598 ) $ 104,823 Condensed Consolidating Statement of (Loss) Income and Comprehensive (Loss) Income Three Months Ended September 30, 2016 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 827,648 $ 1,052,915 $ (25,351 ) $ 1,855,212 Cost of goods sold (excluding depreciation and amortization) — 663,159 852,365 (25,351 ) 1,490,173 Selling, general and administrative expenses 38 128,514 126,995 — 255,547 Depreciation and amortization — 5,114 11,823 — 16,937 Results of affiliates’ operations 100,295 71,567 — (171,862 ) — Interest expense (income), net 4,904 23,543 (7,655 ) — 20,792 Loss on debt redemption 123,933 — — — 123,933 Income tax expense (benefit) 2,441 (12,261 ) (11,329 ) — (21,149 ) Net (loss) income (31,021 ) 91,146 80,716 (171,862 ) (31,021 ) Net income attributable to noncontrolling interests — — 590 — 590 Net (loss) income attributable to WESCO International, Inc. $ (31,021 ) $ 91,146 $ 80,126 $ (171,862 ) $ (31,611 ) Other comprehensive loss: Foreign currency translation adjustments (13,993 ) (13,993 ) (13,993 ) 27,986 (13,993 ) Comprehensive (loss) income attributable to WESCO International, Inc. $ (45,014 ) $ 77,153 $ 66,133 $ (143,876 ) $ (45,604 ) Condensed Consolidating Statement of Income and Comprehensive Income Nine Months Ended September 30, 2017 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 2,490,102 $ 3,289,693 $ (97,420 ) $ 5,682,375 Cost of goods sold (excluding depreciation and amortization) — 2,002,708 2,675,608 (97,420 ) 4,580,896 Selling, general and administrative expenses — 410,624 403,651 — 814,275 Depreciation and amortization — 13,811 33,947 — 47,758 Results of affiliates’ operations 140,915 117,907 — (258,822 ) — Interest expense (income), net — 74,961 (24,114 ) — 50,847 Income tax (benefit) expense — (3,034 ) 50,718 — 47,684 Net income 140,915 108,939 149,883 (258,822 ) 140,915 Net income attributable to noncontrolling interests — — (3 ) — (3 ) Net income attributable to WESCO International, Inc. $ 140,915 $ 108,939 $ 149,886 $ (258,822 ) $ 140,918 Other comprehensive income: Foreign currency translation adjustments 96,097 96,097 96,097 (192,194 ) 96,097 Post retirement benefit plan adjustments 252 252 252 (504 ) 252 Comprehensive income attributable to WESCO International, Inc. $ 237,264 $ 205,288 $ 246,235 $ (451,520 ) $ 237,267 Condensed Consolidating Statement of Income and Comprehensive Income Nine Months Ended September 30, 2016 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 2,481,165 $ 3,140,011 $ (78,421 ) $ 5,542,755 Cost of goods sold (excluding depreciation and amortization) — 1,985,639 2,535,861 (78,421 ) 4,443,079 Selling, general and administrative expenses (328 ) 351,663 448,021 — 799,356 Depreciation and amortization — 15,318 34,951 — 50,269 Results of affiliates’ operations 193,266 105,401 — (298,667 ) — Interest expense (income), net 17,555 63,247 (21,729 ) — 59,073 Loss on debt redemption 123,933 — — — 123,933 Income tax (benefit) expense (1,261 ) 4,677 10,262 — 13,678 Net income 53,367 166,022 132,645 (298,667 ) 53,367 Net loss attributable to noncontrolling interests — — (876 ) — (876 ) Net income attributable to WESCO International, Inc. $ 53,367 $ 166,022 $ 133,521 $ (298,667 ) $ 54,243 Other comprehensive income (loss): Foreign currency translation adjustments 66,512 66,512 66,512 (133,024 ) 66,512 Post retirement benefit plan adjustments (16 ) (16 ) (16 ) 32 (16 ) Comprehensive income attributable to WESCO International, Inc. $ 119,863 $ 232,518 $ 200,017 $ (431,659 ) $ 120,739 Condensed Consolidating Statement of Cash Flows Nine Months Ended September 30, 2017 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net cash (used in) provided by operating activities $ (28,740 ) $ 168,603 $ (58,752 ) $ — $ 81,111 Investing activities: Capital expenditures — (7,435 ) (8,535 ) — (15,970 ) Dividends received from subsidiaries — 51,561 — (51,561 ) — Other — (174,032 ) 16,711 160,811 3,490 Net cash (used in) provided by investing activities — (129,906 ) 8,176 109,250 (12,480 ) Financing activities: Borrowings 135,442 557,391 691,682 (173,907 ) 1,210,608 Repayments — (587,485 ) (617,301 ) 13,096 (1,191,690 ) Repurchases of common stock (106,702 ) — — — (106,702 ) Dividends paid by subsidiaries — — (51,561 ) 51,561 — Other — (4,380 ) — — (4,380 ) Net cash provided by (used in) financing activities 28,740 (34,474 ) 22,820 (109,250 ) (92,164 ) Effect of exchange rate changes on cash and cash equivalents — — 7,485 — 7,485 Net change in cash and cash equivalents — 4,223 (20,271 ) — (16,048 ) Cash and cash equivalents at the beginning of period — 41,552 68,579 — 110,131 Cash and cash equivalents at the end of period $ — $ 45,775 $ 48,308 $ — $ 94,083 Condensed Consolidating Statement of Cash Flows Nine Months Ended September 30, 2016 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net cash provided by (used in) operating activities $ 124,834 $ (274,575 ) $ 366,929 $ — $ 217,188 Investing activities: Capital expenditures — (9,224 ) (3,959 ) — (13,183 ) Acquisition payments, net of cash acquired — (50,745 ) — — (50,745 ) Dividends received from subsidiaries — 47,621 — (47,621 ) — Other — (257,768 ) (335,594 ) 589,477 (3,885 ) Net cash used in investing activities — (270,116 ) (339,553 ) 541,856 (67,813 ) Financing activities: Borrowings 224,043 1,386,397 468,890 (257,768 ) 1,821,562 Repayments (344,804 ) (834,688 ) (500,879 ) (331,709 ) (2,012,080 ) Dividends paid by subsidiaries — — (47,621 ) 47,621 — Other (4,073 ) (3,494 ) — — (7,567 ) Net cash (used in) provided by financing activities (124,834 ) 548,215 (79,610 ) (541,856 ) (198,085 ) Effect of exchange rate changes on cash and cash equivalents — — 1,268 — 1,268 Net change in cash and cash equivalents — 3,524 (50,966 ) — (47,442 ) Cash and cash equivalents at the beginning of period — 38,963 121,316 — 160,279 Cash and cash equivalents at the end of period $ — $ 42,487 $ 70,350 $ — $ 112,837 Revisions As described in Note 2, the Condensed Consolidated Balance Sheet at December 31, 2016 has been revised to correct certain financial statement line items.

Subsequent Events SUBSEQUENT EV

Subsequent Events SUBSEQUENT EVENTS (Notes)	9 Months Ended
	Sep. 30, 2017
Subsequent Events [Abstract]
Subsequent Events [Text Block]	11. SUBSEQUENT EVENTS The Company evaluated subsequent events and concluded that no subsequent events have occurred that would require recognition in the unaudited Condensed Consolidated Financial Statements or disclosure in the Notes thereto.

GOODWILL (Notes)

GOODWILL (Notes)	9 Months Ended
	Sep. 30, 2017
Goodwill [Line Items]
Goodwill Disclosure [Text Block]	4. GOODWILL The following table sets forth the changes in the carrying value of goodwill: Nine Months Ended September 30, September 30, (In thousands) Beginning balance January 1 (1) $ 1,730,950 $ 1,681,662 Foreign currency exchange rate changes 45,968 34,799 Adjustments to goodwill for acquisitions (2) — 19,201 Ending balance September 30 $ 1,776,918 $ 1,735,662 (1) As described in Note 2, the Condensed Consolidated Balance Sheet at December 31, 2016 has been revised to correct certain financial statement line items, including goodwill. (2) For the nine months ended September 30, 2016 , adjustments relate to goodwill resulting from the preliminary allocation of the AED purchase price to the respective assets acquired and liabilities assumed, partially offset by an adjustment to goodwill related to deferred income taxes.

ACCOUNTING POLICIES (Policies)

ACCOUNTING POLICIES (Policies)	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited Condensed Consolidated Financial Statements of WESCO have been prepared in accordance with Rule 10-01 of Regulation S-X of the Securities and Exchange Commission (the “SEC”). The unaudited condensed consolidated financial information should be read in conjunction with the audited Consolidated Financial Statements and Notes thereto included in WESCO’s 2016 Annual Report on Form 10-K as filed with the SEC on February 22, 2017. The Condensed Consolidated Balance Sheet at December 31, 2016 was derived from the audited Consolidated Financial Statements as of that date, but does not include all of the disclosures required by accounting principles generally accepted in the United States of America. The unaudited Condensed Consolidated Balance Sheet as of September 30, 2017 , the unaudited Condensed Consolidated Statements of Income and Comprehensive Income for the three and nine months ended September 30, 2017 and 2016 , respectively, and the unaudited Condensed Consolidated Statements of Cash Flows for the nine months ended September 30, 2017 and 2016 , respectively, in the opinion of management, have been prepared on the same basis as the audited Consolidated Financial Statements and include all adjustments necessary for the fair statement of the results of the interim periods presented herein. All adjustments reflected in the unaudited condensed consolidated financial information are of a normal recurring nature unless indicated. The results for the interim periods presented herein are not necessarily indicative of the results to be expected for the full year.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company’s financial instruments consist of cash and cash equivalents, accounts receivable, accounts payable and other accrued liabilities, and outstanding indebtedness. The reported carrying amounts of WESCO’s financial instruments approximate their fair values. The Company uses a market approach to fair value all of its debt instruments, utilizing quoted prices in active markets, interest rates and other relevant information generated by market transactions involving similar instruments. Therefore, all of the Company's debt instruments are classified as Level 2 within the valuation hierarchy.
New Accounting Pronouncements, Policy [Policy Text Block]	Recently Adopted Accounting Pronouncements In March 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2016-09, Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting , which simplifies several aspects of accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. The amendments in this ASU affect all entities that issue share-based payment awards to their employees. The Company adopted this ASU in the first quarter of 2017. The amendment related to the recognition of excess tax benefits and deficiencies was applied prospectively and, as disclosed in Note 9, lowered the Company's effective tax rate for the nine months ended September 30, 2017 . The amendment related to the presentation of excess tax benefits on the statement of cash flows was also applied prospectively, and did not have a material impact on WESCO's cash flows. The other amendments, which were adopted by the Company according to the respective transition requirements, had no impact on the consolidated financial statements and notes thereto. In October 2016, the FASB issued ASU 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory. The purpose of ASU 2016-16 is to simplify the income tax accounting of an intra-entity transfer of an asset other than inventory and to record its effect when the transfer occurs. The Company early adopted this ASU on a modified retrospective basis in the first quarter of 2017. The adoption of this ASU did not have a material impact on WESCO's financial position and it had no impact on its results of operations or cash flows. Recently Issued Accounting Pronouncements In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers: Deferral of Effective Date . The Company previously reported that in May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers , which provides a framework for addressing revenue recognition issues and replaces almost all existing revenue recognition guidance in current U.S. generally accepted accounting principles. The core principle of ASU 2014-09 is for companies to recognize revenue for the transfer of goods or services to customers in amounts that reflect the consideration to which the company expects to be entitled in exchange for those goods or services. ASU 2014-09 will also result in enhanced disclosures about revenue, provide guidance for transactions that were not previously addressed comprehensively, and improve guidance for multiple-element arrangements. The amendments in ASU 2015-14 defer the effective date of the new revenue recognition guidance to annual reporting periods beginning after December 15, 2017, including interim periods within that reporting period. During 2016, the FASB issued four ASUs that address implementation issues and correct or improve certain aspects of the new revenue recognition guidance, including ASU 2016-08, Principal versus Agent Considerations (Reporting Revenue Gross versus Net) , ASU 2016-10, Identifying Performance Obligations and Licensing , ASU 2016-12, Narrow-Scope Improvements and Practical Expedients and ASU 2016-20, Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers . These ASUs do not change the core principles in the revenue recognition standard outlined above. The Company has developed a multiphase plan and established a cross-functional team to evaluate and implement the new standard. Management has completed the diagnostic phase, which involved reviewing various customer contracts and comparing current accounting to the requirements of the new standard. Currently management is evaluating the new disclosure requirements and identifying and implementing appropriate changes to its business processes and controls to support recognition and disclosure under the new standard. The new standard will be adopted in the first quarter of 2018 and the Company expects to use the modified retrospective approach. Management will continue to evaluate the impact that this pronouncement may have on WESCO's consolidated financial statements and notes thereto. In February 2016, the FASB issued ASU 2016-02, Leases , a comprehensive new standard that amends various aspects of existing accounting guidance for leases, including the recognition of a right-of-use asset and a lease liability on the balance sheet and disclosing key information about leasing arrangements. This guidance is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Early adoption is permitted. The new leasing standard requires modified retrospective transition, which requires application of the new guidance at the beginning of the earliest comparative period presented in the year of adoption. Management is currently evaluating the impact of this new standard on WESCO's consolidated financial statements and notes thereto. In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , which introduces new guidance for the accounting for credit losses on certain financial instruments. The amendments in ASU 2016-13 are effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years and early adoption is permitted. Management is currently evaluating the impact of this accounting standard on WESCO's consolidated financial statements and notes thereto. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (a consensus of the Emerging Issues Task Force) . This ASU provides guidance on eight specific cash flow issues where there is diversity in practice. The amendments in this ASU are effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted, including adoption in an interim period. Management is currently evaluating the impact of this accounting standard on WESCO's consolidated financial statements and notes thereto. In January 2017, the FASB issued ASU 2017-04, Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment, which eliminates Step 2 from the goodwill impairment test. Under the amendments in this update, an entity should perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. An entity should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. An entity should apply the amendments in this ASU on a prospective basis. This guidance is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Management has not yet evaluated the impact of this accounting standard on WESCO's consolidated financial statements and notes thereto. In March 2017, the FASB issued ASU 2017-07, Compensation—Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost . Presently, net benefit cost is reported as an employee cost within operating income (or capitalized into assets when appropriate). This amendment requires the bifurcation of net benefit cost. The service component will be presented with other employee compensation costs in operating income (or capitalized in assets). The other components will be reported separately outside of operations, and will not be eligible for capitalization. This guidance is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. Early adoption is permitted. Management has not yet evaluated the impact of this accounting standard on WESCO's consolidated financial statements and notes thereto. In May 2017, the FASB issued ASU 2017-09, Compensation—Stock Compensation (Topic 718): Scope of Modification Accounting , which clarifies when to account for a change to the terms or conditions of a share-based payment award as a modification. Under the new guidance, modification accounting is required only if the fair value, the vesting conditions, or the classification of the award (as equity or liability) changes as a result of the change in terms or conditions. The guidance is effective prospectively for all companies for annual periods beginning on or after December 15, 2017. Early adoption is permitted. Management has not yet evaluated the impact of this accounting standard on WESCO's consolidated financial statements and notes thereto. Other pronouncements issued by the FASB or other authoritative accounting standards groups with future effective dates are either not applicable or are not expected to be significant to WESCO’s financial position, results of operations or cash flows.
Comparability of Prior Year Financial Data, Policy [Policy Text Block]	Revision of Prior Period Financial Statements In the third quarter of 2017, management determined that the Company's income taxes receivable and payable and other tax account balances were overstated as of December 31, 2016 by a cumulative net amount of $46.4 million , which related to multiple prior periods. The Company also identified a $10.2 million understatement related to deferred income taxes and goodwill. In accordance with Staff Accounting Bulletin (“SAB”) No. 99, Materiality , and SAB No. 108, Considering the Effects of Prior Year Misstatements when Quantifying Misstatements in Current Year Financial Statements , management concluded that these misstatements are not material to the Company's previously issued annual and interim financial statements. Correcting the effected financial statement line items in the quarterly period ended September 30, 2017 would materially misstate the condensed consolidated financial information presented herein. Accordingly, the Condensed Consolidated Balance Sheet at December 31, 2016 in this Quarterly Report on Form 10-Q has been revised. There was an immaterial effect on the Condensed Consolidated Statements of Income and Comprehensive Income for the three and nine months ended September 30, 2016 , and no effect on the Condensed Consolidated Statements of Cash Flows for the respective periods presented herein. Periods not presented herein will be revised, as applicable, in future filings. The following table presents the effects on the financial statement line items that were revised: December 31, 2016 As Reported Adjustment As Revised (In thousands) Prepaid expenses and other current assets $ 121,464 $ (69,379 ) $ 52,085 Total current assets 2,172,457 (69,379 ) 2,103,078 Goodwill 1,720,714 10,236 1,730,950 Total assets 4,490,984 (59,143 ) 4,431,841 Other current liabilities 111,304 (22,998 ) 88,306 Total current liabilities 896,797 (22,998 ) 873,799 Deferred income taxes 158,009 10,236 168,245 Total liabilities 2,480,972 (12,762 ) 2,468,210 Retained earnings 1,956,532 (41,775 ) 1,914,757 Accumulated other comprehensive loss (387,365 ) (4,606 ) (391,971 ) Total stockholders' equity 2,010,012 (46,381 ) 1,963,631 Total liabilities and stockholders' equity 4,490,984 (59,143 ) 4,431,841

ACCOUNTING POLICIES Revision (T

ACCOUNTING POLICIES Revision (Tables)	9 Months Ended
	Sep. 30, 2017
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Schedule of Quantifying Prior Year Misstatements Corrected in Current Year Financial Statements [Table Text Block]	The following table presents the effects on the financial statement line items that were revised: December 31, 2016 As Reported Adjustment As Revised (In thousands) Prepaid expenses and other current assets $ 121,464 $ (69,379 ) $ 52,085 Total current assets 2,172,457 (69,379 ) 2,103,078 Goodwill 1,720,714 10,236 1,730,950 Total assets 4,490,984 (59,143 ) 4,431,841 Other current liabilities 111,304 (22,998 ) 88,306 Total current liabilities 896,797 (22,998 ) 873,799 Deferred income taxes 158,009 10,236 168,245 Total liabilities 2,480,972 (12,762 ) 2,468,210 Retained earnings 1,956,532 (41,775 ) 1,914,757 Accumulated other comprehensive loss (387,365 ) (4,606 ) (391,971 ) Total stockholders' equity 2,010,012 (46,381 ) 1,963,631 Total liabilities and stockholders' equity 4,490,984 (59,143 ) 4,431,841

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	9 Months Ended
	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]	During the three and nine months ended September 30, 2017 and 2016 , WESCO granted the following stock-settled stock appreciation rights, restricted stock units and performance-based awards at the following weighted-average fair values: Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, Stock-settled stock appreciation rights granted 12,076 1,745 455,807 709,999 Weighted-average fair value $ 15.74 $ 16.68 $ 20.52 $ 12.91 Restricted stock units granted 2,313 — 100,993 143,305 Weighted-average fair value $ 57.30 $ — $ 71.33 $ 42.45 Performance-based awards granted — — 39,978 91,768 Weighted-average fair value $ — $ — $ 76.63 $ 47.00
Schedule of Share-based Compensation, Stock Options and Stock Appreciation Rights Award Activity [Table Text Block]	The following table sets forth a summary of stock-settled stock appreciation rights and related information for the nine months ended September 30, 2017 : Awards Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (In years) Aggregate Intrinsic Value (In thousands) Outstanding at December 31, 2016 2,439,487 $ 52.62 Granted 455,807 71.21 Exercised (472,873 ) 42.41 Forfeited (143,506 ) 66.21 Outstanding at September 30, 2017 2,278,915 57.60 6.4 $ 18,344 Exercisable at September 30, 2017 1,359,744 $ 56.71 4.8 $ 12,212
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 nine months ended September 30, 2017 : Awards Weighted- Average Fair Value Unvested at December 31, 2016 257,096 $ 57.47 Granted 100,993 71.33 Vested (43,780 ) 85.13 Forfeited (18,022 ) 55.96 Unvested at September 30, 2017 296,287 $ 58.20
Schedule of Nonvested Performance-based Units Activity [Table Text Block]	The following table sets forth a summary of performance-based awards for the nine months ended September 30, 2017 : Awards Weighted- Average Fair Value Unvested at December 31, 2016 149,320 $ 60.36 Granted 39,978 76.63 Vested — — Forfeited (39,650 ) 77.40 Unvested at September 30, 2017 149,648 $ 60.19
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 Nine Months Ended September 30, September 30, September 30, September 30, Risk free interest rate 1.8 % 1.3 % 1.9 % 1.2 % Expected life (in years) 5 5 5 5 Expected volatility 28 % 31 % 29 % 32 %
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]	The fair value of the performance shares granted during the nine months ended September 30, 2017 and 2016 was estimated using the following weighted-average assumptions: Nine Months Ended September 30, September 30, Grant date share price $ 71.65 $ 42.44 WESCO expected volatility 29 % 26 % Peer group median volatility 24 % 24 % Risk-free interest rate 1.5 % 0.9 % Correlation of peer company returns 114 % 122 %

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]	The following table sets forth the details of basic and diluted earnings per share: Three Months Ended Nine Months Ended September 30, September 30, (In thousands, except per share data) 2017 2016 2017 2016 Net income (loss) attributable to WESCO International, Inc. $ 53,675 $ (31,611 ) $ 140,918 $ 54,243 Weighted-average common shares outstanding used in computing basic earnings per share 47,415 43,378 48,134 42,611 Common shares issuable upon exercise of dilutive equity awards 389 511 508 519 Common shares issuable from contingently convertible debentures (see below for basis of calculation) — 4,851 — 4,908 Weighted-average common shares outstanding and common share equivalents, diluted 47,804 48,740 48,642 48,038 Weighted-average common shares outstanding and common share equivalents used in computing diluted earnings per share 47,804 43,378 48,642 48,038 Earnings (loss) per share attributable to WESCO International, Inc. Basic $ 1.13 $ (0.73 ) $ 2.93 $ 1.27 Diluted $ 1.12 $ (0.73 ) $ 2.90 $ 1.13

EMPLOYEE BENEFIT PLANS Schedule

EMPLOYEE BENEFIT PLANS Schedule of Net Benefit Costs (Tables)	9 Months Ended
	Sep. 30, 2017
Postemployment Benefits [Abstract]
Schedule of Net Benefit Costs [Table Text Block]	The following table reflects the components of net periodic benefit costs for the defined benefit plans: Three Months Ended Nine Months Ended September 30, September 30, (In thousands of dollars) 2017 2016 2017 2016 Service cost $ 1,118 $ 977 $ 3,234 $ 2,889 Interest cost 1,007 979 2,915 2,898 Expected return on plan assets (1,432 ) (1,353 ) (4,144 ) (4,004 ) Recognized actuarial gain (51 ) (10 ) (149 ) (31 ) Net periodic benefit cost $ 642 $ 593 $ 1,856 $ 1,752

OTHER FINANCIAL INFORMATION (Ta

OTHER FINANCIAL INFORMATION (Tables)	9 Months Ended
	Sep. 30, 2017
Condensed Balance Sheet Statements, Captions [Line Items]
Condensed Balance Sheet [Table Text Block]	Condensed Consolidating Balance Sheet December 31, 2016 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Cash and cash equivalents $ — $ 41,552 $ 68,579 $ — $ 110,131 Trade accounts receivable, net — — 1,034,402 — 1,034,402 Inventories — 364,562 456,879 — 821,441 Prepaid expenses and other current assets 13,647 34,833 211,637 (123,013 ) 137,104 Total current assets 13,647 440,947 1,771,497 (123,013 ) 2,103,078 Intercompany receivables, net — — 2,060,336 (2,060,336 ) — Property, buildings and equipment, net — 51,824 105,783 — 157,607 Intangible assets, net — 3,417 389,945 — 393,362 Goodwill — 257,623 1,473,327 — 1,730,950 Investments in affiliates 3,538,476 4,028,502 — (7,566,978 ) — Other assets — 23,846 22,998 — 46,844 Total assets $ 3,552,123 $ 4,806,159 $ 5,823,886 $ (9,750,327 ) $ 4,431,841 Accounts payable $ — $ 381,795 $ 302,926 $ — $ 684,721 Short-term debt — — 20,920 — 20,920 Other current liabilities — 120,299 170,872 (123,013 ) 168,158 Total current liabilities — 502,094 494,718 (123,013 ) 873,799 Intercompany payables, net 1,572,486 487,850 — (2,060,336 ) — Long-term debt, net — 983,449 379,686 — 1,363,135 Other noncurrent liabilities 12,737 55,898 162,641 — 231,276 Total WESCO International, Inc. stockholders' equity 1,966,900 2,776,868 4,790,110 (7,566,978 ) 1,966,900 Noncontrolling interests — — (3,269 ) — (3,269 ) Total liabilities and stockholders’ equity $ 3,552,123 $ 4,806,159 $ 5,823,886 $ (9,750,327 ) $ 4,431,841 Condensed Consolidating Balance Sheet September 30, 2017 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Cash and cash equivalents $ — $ 45,775 $ 48,308 $ — $ 94,083 Trade accounts receivable, net — — 1,236,612 — 1,236,612 Inventories — 403,752 521,297 — 925,049 Prepaid expenses and other current assets 13,642 42,130 203,991 (105,380 ) 154,383 Total current assets 13,642 491,657 2,010,208 (105,380 ) 2,410,127 Intercompany receivables, net — — 2,141,945 (2,141,945 ) — Property, buildings and equipment, net — 50,191 107,400 — 157,591 Intangible assets, net — 2,932 375,221 — 378,153 Goodwill — 257,623 1,519,295 — 1,776,918 Investments in affiliates 3,817,521 4,228,307 — (8,045,828 ) — Other assets — 18,615 23,064 — 41,679 Total assets $ 3,831,163 $ 5,049,325 $ 6,177,133 $ (10,293,153 ) $ 4,764,468 Accounts payable $ — $ 443,675 $ 394,752 $ — $ 838,427 Short-term debt — — 39,712 — 39,712 Other current liabilities — 117,701 153,033 (105,380 ) 165,354 Total current liabilities — 561,376 587,497 (105,380 ) 1,043,493 Intercompany payables, net 1,707,926 434,019 — (2,141,945 ) — Long-term debt, net — 968,361 399,940 — 1,368,301 Other noncurrent liabilities 12,733 61,635 171,073 — 245,441 Total WESCO International, Inc. stockholders' equity 2,110,504 3,023,934 5,021,894 (8,045,828 ) 2,110,504 Noncontrolling interests — — (3,271 ) — (3,271 ) Total liabilities and stockholders’ equity $ 3,831,163 $ 5,049,325 $ 6,177,133 $ (10,293,153 ) $ 4,764,468

OTHER FINANCIAL INFORMATION Con

OTHER FINANCIAL INFORMATION Condensed Income Statement (Tables)	9 Months Ended
	Sep. 30, 2017
Condensed Income Statements, Captions [Line Items]
Condensed Income Statement [Table Text Block]	Condensed Consolidating Statement of (Loss) Income and Comprehensive (Loss) Income Three Months Ended September 30, 2016 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 827,648 $ 1,052,915 $ (25,351 ) $ 1,855,212 Cost of goods sold (excluding depreciation and amortization) — 663,159 852,365 (25,351 ) 1,490,173 Selling, general and administrative expenses 38 128,514 126,995 — 255,547 Depreciation and amortization — 5,114 11,823 — 16,937 Results of affiliates’ operations 100,295 71,567 — (171,862 ) — Interest expense (income), net 4,904 23,543 (7,655 ) — 20,792 Loss on debt redemption 123,933 — — — 123,933 Income tax expense (benefit) 2,441 (12,261 ) (11,329 ) — (21,149 ) Net (loss) income (31,021 ) 91,146 80,716 (171,862 ) (31,021 ) Net income attributable to noncontrolling interests — — 590 — 590 Net (loss) income attributable to WESCO International, Inc. $ (31,021 ) $ 91,146 $ 80,126 $ (171,862 ) $ (31,611 ) Other comprehensive loss: Foreign currency translation adjustments (13,993 ) (13,993 ) (13,993 ) 27,986 (13,993 ) Comprehensive (loss) income attributable to WESCO International, Inc. $ (45,014 ) $ 77,153 $ 66,133 $ (143,876 ) $ (45,604 ) Condensed Consolidating Statement of Income and Comprehensive Income Three Months Ended September 30, 2017 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 867,973 $ 1,169,377 $ (37,191 ) $ 2,000,159 Cost of goods sold (excluding depreciation and amortization) — 697,896 954,109 (37,191 ) 1,614,814 Selling, general and administrative expenses — 140,638 139,383 — 280,021 Depreciation and amortization — 4,475 11,599 — 16,074 Results of affiliates’ operations 53,576 42,726 — (96,302 ) — Interest expense (income), net — 25,436 (8,125 ) — 17,311 Income tax (benefit) expense — (136 ) 18,499 — 18,363 Net income 53,576 42,390 53,912 (96,302 ) 53,576 Net income attributable to noncontrolling interests — — (99 ) — (99 ) Net income attributable to WESCO International, Inc. $ 53,576 $ 42,390 $ 54,011 $ (96,302 ) $ 53,675 Other comprehensive income: Foreign currency translation adjustments 51,148 51,148 51,148 (102,296 ) 51,148 Comprehensive income attributable to WESCO International, Inc. $ 104,724 $ 93,538 $ 105,159 $ (198,598 ) $ 104,823 Condensed Consolidating Statement of Income and Comprehensive Income Nine Months Ended September 30, 2016 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 2,481,165 $ 3,140,011 $ (78,421 ) $ 5,542,755 Cost of goods sold (excluding depreciation and amortization) — 1,985,639 2,535,861 (78,421 ) 4,443,079 Selling, general and administrative expenses (328 ) 351,663 448,021 — 799,356 Depreciation and amortization — 15,318 34,951 — 50,269 Results of affiliates’ operations 193,266 105,401 — (298,667 ) — Interest expense (income), net 17,555 63,247 (21,729 ) — 59,073 Loss on debt redemption 123,933 — — — 123,933 Income tax (benefit) expense (1,261 ) 4,677 10,262 — 13,678 Net income 53,367 166,022 132,645 (298,667 ) 53,367 Net loss attributable to noncontrolling interests — — (876 ) — (876 ) Net income attributable to WESCO International, Inc. $ 53,367 $ 166,022 $ 133,521 $ (298,667 ) $ 54,243 Other comprehensive income (loss): Foreign currency translation adjustments 66,512 66,512 66,512 (133,024 ) 66,512 Post retirement benefit plan adjustments (16 ) (16 ) (16 ) 32 (16 ) Comprehensive income attributable to WESCO International, Inc. $ 119,863 $ 232,518 $ 200,017 $ (431,659 ) $ 120,739 Condensed Consolidating Statement of Income and Comprehensive Income Nine Months Ended September 30, 2017 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 2,490,102 $ 3,289,693 $ (97,420 ) $ 5,682,375 Cost of goods sold (excluding depreciation and amortization) — 2,002,708 2,675,608 (97,420 ) 4,580,896 Selling, general and administrative expenses — 410,624 403,651 — 814,275 Depreciation and amortization — 13,811 33,947 — 47,758 Results of affiliates’ operations 140,915 117,907 — (258,822 ) — Interest expense (income), net — 74,961 (24,114 ) — 50,847 Income tax (benefit) expense — (3,034 ) 50,718 — 47,684 Net income 140,915 108,939 149,883 (258,822 ) 140,915 Net income attributable to noncontrolling interests — — (3 ) — (3 ) Net income attributable to WESCO International, Inc. $ 140,915 $ 108,939 $ 149,886 $ (258,822 ) $ 140,918 Other comprehensive income: Foreign currency translation adjustments 96,097 96,097 96,097 (192,194 ) 96,097 Post retirement benefit plan adjustments 252 252 252 (504 ) 252 Comprehensive income attributable to WESCO International, Inc. $ 237,264 $ 205,288 $ 246,235 $ (451,520 ) $ 237,267

OTHER FINANCIAL INFORMATION C24

OTHER FINANCIAL INFORMATION Condensed Cash Flow Statement (Tables)	9 Months Ended
	Sep. 30, 2017
Condensed Cash Flow Statements, Captions [Line Items]
Condensed Cash Flow Statement [Table Text Block]	Condensed Consolidating Statement of Cash Flows Nine Months Ended September 30, 2016 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net cash provided by (used in) operating activities $ 124,834 $ (274,575 ) $ 366,929 $ — $ 217,188 Investing activities: Capital expenditures — (9,224 ) (3,959 ) — (13,183 ) Acquisition payments, net of cash acquired — (50,745 ) — — (50,745 ) Dividends received from subsidiaries — 47,621 — (47,621 ) — Other — (257,768 ) (335,594 ) 589,477 (3,885 ) Net cash used in investing activities — (270,116 ) (339,553 ) 541,856 (67,813 ) Financing activities: Borrowings 224,043 1,386,397 468,890 (257,768 ) 1,821,562 Repayments (344,804 ) (834,688 ) (500,879 ) (331,709 ) (2,012,080 ) Dividends paid by subsidiaries — — (47,621 ) 47,621 — Other (4,073 ) (3,494 ) — — (7,567 ) Net cash (used in) provided by financing activities (124,834 ) 548,215 (79,610 ) (541,856 ) (198,085 ) Effect of exchange rate changes on cash and cash equivalents — — 1,268 — 1,268 Net change in cash and cash equivalents — 3,524 (50,966 ) — (47,442 ) Cash and cash equivalents at the beginning of period — 38,963 121,316 — 160,279 Cash and cash equivalents at the end of period $ — $ 42,487 $ 70,350 $ — $ 112,837 Condensed Consolidating Statement of Cash Flows Nine Months Ended September 30, 2017 (In thousands of dollars) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net cash (used in) provided by operating activities $ (28,740 ) $ 168,603 $ (58,752 ) $ — $ 81,111 Investing activities: Capital expenditures — (7,435 ) (8,535 ) — (15,970 ) Dividends received from subsidiaries — 51,561 — (51,561 ) — Other — (174,032 ) 16,711 160,811 3,490 Net cash (used in) provided by investing activities — (129,906 ) 8,176 109,250 (12,480 ) Financing activities: Borrowings 135,442 557,391 691,682 (173,907 ) 1,210,608 Repayments — (587,485 ) (617,301 ) 13,096 (1,191,690 ) Repurchases of common stock (106,702 ) — — — (106,702 ) Dividends paid by subsidiaries — — (51,561 ) 51,561 — Other — (4,380 ) — — (4,380 ) Net cash provided by (used in) financing activities 28,740 (34,474 ) 22,820 (109,250 ) (92,164 ) Effect of exchange rate changes on cash and cash equivalents — — 7,485 — 7,485 Net change in cash and cash equivalents — 4,223 (20,271 ) — (16,048 ) Cash and cash equivalents at the beginning of period — 41,552 68,579 — 110,131 Cash and cash equivalents at the end of period $ — $ 45,775 $ 48,308 $ — $ 94,083

GOODWILL (Tables)

GOODWILL (Tables)	9 Months Ended
	Sep. 30, 2017
Goodwill [Line Items]
Schedule of Goodwill [Table Text Block]	Nine Months Ended September 30, September 30, (In thousands) Beginning balance January 1 (1) $ 1,730,950 $ 1,681,662 Foreign currency exchange rate changes 45,968 34,799 Adjustments to goodwill for acquisitions (2) — 19,201 Ending balance September 30 $ 1,776,918 $ 1,735,662

ORGANIZATION (Details)

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

ACCOUNTING POLICIES (Details)

ACCOUNTING POLICIES (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Prepaid expenses and other current assets	$ 71,795
Assets, Current	2,410,127	$ 2,103,078
Goodwill	1,776,918	1,730,950	$ 1,735,662	$ 1,681,662
Liabilities and Equity	4,764,468	4,431,841
Other Accrued Liabilities, Current	87,143
Liabilities, Current	1,043,493	873,799
Assets	4,764,468	4,431,841
Deferred Tax Liabilities, Net, Noncurrent	179,630
Liabilities	2,657,235	2,468,210
Retained earnings	2,056,961
Accumulated other comprehensive income	(295,622)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		(46,381)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 2,107,233	1,963,631
Scenario, Previously Reported [Member]
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Prepaid expenses and other current assets		121,464
Assets, Current		2,172,457
Goodwill		1,720,714
Liabilities and Equity		4,490,984
Other Accrued Liabilities, Current		111,304
Liabilities, Current		896,797
Assets		4,490,984
Deferred Tax Liabilities, Net, Noncurrent		158,009
Liabilities		2,480,972
Retained earnings		1,956,532
Accumulated other comprehensive income		(387,365)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		2,010,012
Scenario, Adjustment [Member]
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Prepaid expenses and other current assets		(69,379)
Assets, Current		(69,379)
Goodwill		10,236
Liabilities and Equity		(59,143)
Other Accrued Liabilities, Current		(22,998)
Liabilities, Current		(22,998)
Assets		(59,143)
Deferred Tax Liabilities, Net, Noncurrent		10,236
Liabilities		(12,762)
Retained earnings		(41,775)
Accumulated other comprehensive income		(4,606)
Restatement Adjustment [Member]
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Prepaid expenses and other current assets		52,085
Assets, Current		2,103,078
Goodwill		1,730,950
Liabilities and Equity		4,431,841
Other Accrued Liabilities, Current		88,306
Liabilities, Current		873,799
Assets		4,431,841
Deferred Tax Liabilities, Net, Noncurrent		168,245
Liabilities		2,468,210
Retained earnings		1,914,757
Accumulated other comprehensive income		(391,971)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		$ 1,963,631

ACQUISITIONS - ACQUISITIONS (De

ACQUISITIONS - ACQUISITIONS (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2017USD ($)branches	Sep. 30, 2016USD ($)
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	$ 0	$ 50,745
Number of Stores | branches	500
Atlanta Electrical Distributors, LLC (AED) [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition	Mar. 14, 2016
Business Acquisition, Name of Acquired Entity	Atlanta Electrical Distributors, LLC
Business Acquisition, Revenue Reported by Acquired Entity for Last Annual Period	$ 85,000
Finite-lived Intangible Assets Acquired	21,800
Goodwill, Acquired During Period	$ 30,000
Number of Stores	5
Customer Relationships [Member] | Atlanta Electrical Distributors, LLC (AED) [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired	$ 15,800
Noncompete Agreements [Member] | Atlanta Electrical Distributors, LLC (AED) [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired	$ 100
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	5 years
Trademarks [Member] | Atlanta Electrical Distributors, LLC (AED) [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired	$ 6,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	13 years
Minimum [Member] | Customer Relationships [Member] | Atlanta Electrical Distributors, LLC (AED) [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	13 years
Maximum [Member] | Customer Relationships [Member] | Atlanta Electrical Distributors, LLC (AED) [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	14 years

SCHEDULE OF SHARE-BASED COMPENS

SCHEDULE OF SHARE-BASED COMPENSATION, STOCK OPTIONS AND STOCK APPRECIATION RIGHTS AWARD ACTIVITY (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Share-based Compensation Arrangement By Share-based Payment Award, Options and Stock Appreciation Rights, Outstanding [Roll Forward]
Weighted Average Exercise Price, Exercises in Period (in dollars per share)			$ 42.41
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value			$ 71.21
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	$ 12,212		$ 12,212
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$ 57.60		$ 57.60		$ 52.62
Share-based Compensation Arrangement By Share-based Payment Award, Options and Stock Appreciation Rights, Outstanding [Roll Forward]
Beginning of Year (in shares)	1,359,744		1,359,744
Grants in Period (in shares)	12,076	1,745	455,807	709,999
Exercises in Period (in shares)			472,873
Forfeitures in Period (in shares)			143,506
Weighted Average Exercise Price, Forfeitures in Period (in dollars per share)			$ 66.21
Weighted Average Exercise Price, Exercisable (in dollars per share)	$ 56.71		$ 56.71
Weighted Average Remaining Contractual Term, Outstanding (in years)			6 years 5 months 6 days
Weighted Average Remaining Contractual Term, Exercisable (in years)			4 years 9 months 6 days
Aggregate Intrinsic Value, Outstanding	$ 18,344		$ 18,344
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number	2,278,915		2,278,915		2,439,487

SCHEDULE OF SHARE-BASED PAYMENT

SCHEDULE OF SHARE-BASED PAYMENT AWARD, VALUATION ASSUMPTIONS (Details) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate	1.80%	1.30%	1.90%	1.20%
Expected life (in years)	5 years	5 years	5 years	5 years
WESCO expected volatility	28.00%	31.00%	29.00%	32.00%
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	12,076	1,745	455,807	709,999
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 16	$ 16.68	$ 20.52	$ 12.91
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	2,313	0	100,993	143,305
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 57.30	$ 0	$ 71.33	$ 42.45
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	0	0	39,978	91,768
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 0	$ 0	$ 76.63	$ 47
Risk free interest rate			0.00%	0.00%
WESCO expected volatility			0.00%	0.00%

SUMMARY OF RESTRICTED STOCK UNI

SUMMARY OF RESTRICTED STOCK UNITS (Details) - Restricted Stock Units (RSUs) [Member] - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Unvested (in shares)	296,287		296,287		257,096
Granted (in shares)	2,313	0	100,993	143,305
Vested (in shares)			(43,780)
Forfeited (in shares)			(18,022)
Unvested, Weighted Average Fair Value (in dollars per share)	$ 58.20		$ 58.20		$ 57.47
Granted, Weighted Average Fair Value (in dollars per share)	$ 57.30	$ 0	71.33	$ 42.45
Vested in Period, Weighted Average Fair Value (in dollars per share)			85.13
Forfeited in Period, Weighted Average Fair Value (in dollars per share)			$ 55.96

SUMMARY OF PERFORMANCE-BASED AW

SUMMARY OF PERFORMANCE-BASED AWARDS (Details) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Unvested (in shares)	149,648		149,648		149,320
Granted (in shares)	0	0	39,978	91,768
Vested (in shares)			0
Forfeited (in shares)			(39,650)
Unvested, Weighted Average Fair Value (in dollars per share)	$ 60.19		$ 60.19		$ 60.36
Granted, Weighted Average Fair Value (in dollars per share)	$ 0	$ 0	76.63	$ 47
Vested in Period, Weighted Average Fair Value (in dollars per share)			0
Forfeited in Period, Weighted Average Fair Value (in dollars per share)			$ 77.40
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)	74,824		74,824

SCHEDULE OF SHARE-BASED PAYME33

SCHEDULE OF SHARE-BASED PAYMENT AWARD, PERFORMANCE-BASED AWARDS, VALUATION ASSUMPTIONS (Details) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
WESCO expected volatility	28.00%	31.00%	29.00%	32.00%
Risk free interest rate	1.80%	1.30%	1.90%	1.20%
Correlation			0.00%	0.00%
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Exercise Price	$ 71.65	$ 42.44	$ 71.65	$ 42.44
WESCO expected volatility			0.00%	0.00%
Risk free interest rate			0.00%	0.00%

STOCK-BASED COMPENSATION (Detai

STOCK-BASED COMPENSATION (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended		12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 3.5	$ 3.4	$ 11.3	$ 10.4
Total unrecognized compensation cost		$ 22.6		$ 22.6
Share-based Compensation Award, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance-based awards outstanding (in shares)		74,824		74,824
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)		74,824		74,824
Scenario, Forecast [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 3.7					$ 0.8	$ 6.7	$ 11.4

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		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net income (loss) attributable to WESCO International, Inc.	$ 53,675	$ (31,611)	$ 140,918	$ 54,243
Weighted average common shares outstanding used in computing basic earnings per share (in shares)	47,415	43,378	48,134	42,611
Common shares issuable upon exercise of dilutive stock options (in shares)	389	511	508	519
Common shares issuable from contingently convertible debentures (in shares)	0	4,851	0	4,908
Weighted average common shares outstanding and common share equivalents used in computing diluted earnings per share (in shares)	47,804	48,740	48,642	48,038
Earnings Per Share, Basic and Diluted [Abstract]
Basic (in dollars per share)	$ 1.13	$ (0.73)	$ 2.93	$ 1.27
Diluted (in dollars per share)	$ 1.12	$ (0.73)	$ 2.90	$ 1.13

EARNINGS PER SHARE (Details)

EARNINGS PER SHARE (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Earnings Per Share Dilution Limit (in shares)	0	4,851,000	0	4,908,000
Debt Instrument, Call Date, Earliest			Sep. 15, 2016
Convertible Debt Securities [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Debt Instrument, Convertible, Conversion Price (in dollars per share)	$ 28.87		$ 28.87
Dilutive Securities, Effect on Basic Earnings Per Share				$ 0.13
Equity Award [Domain]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,500,000		1,300,000	1,300,000
Convertible Debt Securities [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Earnings Per Share Dilution Limit (in shares)			11,951,932

EARNINGS PER SHARE Accelerated

EARNINGS PER SHARE Accelerated Share Repurchase (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2015
Accelerated Share Repurchases [Line Items]
Payments for Repurchase of Common Stock			$ (106,702)	$ (4,073)
Stock Repurchase Program, Authorized Amount	$ 300,000		$ 300,000
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)	$ (50,000)			$ (150,000)
Treasury Stock, Shares, Acquired	974,246	804,291
Treasury Stock, Common, Shares	2,468,576		2,468,576

EMPLOYEE BENEFIT PLANS (Details

EMPLOYEE BENEFIT PLANS (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Retirement Benefits [Abstract]
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 0.5		$ 1.4
Schedule of Employee Benefit Plans [Line Items]
Postemployment Benefits, Period Expense		$ 20.3	$ 18.1
Deferred Compensation Liability, Classified, Noncurrent		$ 23.4		$ 21.7
CANADA | Minimum [Member]
Schedule of Employee Benefit Plans [Line Items]
Defined Contribution Plan Employer Matching Contribution Percent		3.00%
CANADA | Maximum [Member]
Schedule of Employee Benefit Plans [Line Items]
Defined Contribution Plan Employer Matching Contribution Percent		5.00%
UNITED STATES
Schedule of Employee Benefit Plans [Line Items]
Defined Contribution Plan, Employer Matching Contribution, Percent of Match		50.00%
Defined Contribution Plan Employer Matching Contribution Percent		6.00%

EMPLOYEE BENEFIT PLANS EMPLOYEE

EMPLOYEE BENEFIT PLANS EMPLOYEE BENEFIT PLANS Pension Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Retirement Benefits [Abstract]
Defined Benefit Plan, Plan Assets, Contributions by Employer		$ 500		$ 1,400
Service cost	$ 1,118	977	$ 3,234	2,889
Interest cost	1,007	979	2,915	2,898
Expected return on plan assets	(1,432)	(1,353)	(4,144)	(4,004)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(51)	(10)	(149)	(31)
Net periodic benefit cost	$ 642	$ 593	$ 1,856	$ 1,752

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Tax Contingency [Line Items]
Effective tax rate	25.50%	40.53862%	25.30%	20.40122%
Debt Instrument, Call Date, Earliest			Sep. 15, 2016
Federal statutory rate			35.00%
Unrecognized Tax Benefits			$ 1.6
Unrecognized Tax Benefits	$ 4.6		4.6
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	6		6
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	0.2		0.2
Settlement with Taxing Authority [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 0.2		$ 0.2

OTHER FINANCIAL INFORMATION (De

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

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Condensed Financial Information [Line Items]
Cash and cash equivalents	$ 94,083	$ 110,131	$ 112,837	$ 160,279
Trade accounts receivable, net	1,236,612	1,034,402
Inventories, net	925,049	821,441
Prepaid Expense and Other Assets, Current	71,795
Total current assets	2,410,127	2,103,078
Property, buildings and equipment, net	157,591	157,607
Intangible assets, net	378,153	393,362
Goodwill and other intangibles, net	1,776,918	1,730,950	1,735,662	1,681,662
Other assets	41,679	46,844
Total assets	4,764,468	4,431,841
Accounts payable	838,427	684,721
Short-term debt	39,712	20,920
Total current liabilities	1,043,493	873,799
Long-term Debt, Excluding Current Maturities	1,368,301	1,363,135
Total stockholders' equity	2,110,504	1,966,900
Stockholders' Equity Attributable to Noncontrolling Interest	3,271	3,269
Total liabilities and stockholders' equity	4,764,468	4,431,841
Parent Company [Member]
Condensed Financial Information [Line Items]
Cash and cash equivalents	0	0	0	0
Trade accounts receivable, net	0	0
Inventories, net	0	0
Prepaid Expense and Other Assets, Current	13,642	13,647
Total current assets	13,642	13,647
Intercompany receivables, net	0	0
Property, buildings and equipment, net	0	0
Intangible assets, net	0	0
Goodwill and other intangibles, net	0	0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	3,817,521	3,538,476
Other assets	0	0
Total assets	3,831,163	3,552,123
Accounts payable	0	0
Short-term debt	0	0
Other Liabilities, Current	0	0
Total current liabilities	0	0
Intercompany payables, net	1,707,926	1,572,486
Long-term Debt, Excluding Current Maturities	0	0
Liabilities, Other than Long-term Debt, Noncurrent	12,733	12,737
Total stockholders' equity	2,110,504	1,966,900
Stockholders' Equity Attributable to Noncontrolling Interest	0	0
Total liabilities and stockholders' equity	3,831,163	3,552,123
Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Cash and cash equivalents	45,775	41,552	42,487	38,963
Trade accounts receivable, net	0	0
Inventories, net	403,752	364,562
Prepaid Expense and Other Assets, Current	42,130	34,833
Total current assets	491,657	440,947
Intercompany receivables, net	0	0
Property, buildings and equipment, net	50,191	51,824
Intangible assets, net	2,932	3,417
Goodwill and other intangibles, net	257,623	257,623
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	4,228,307	4,028,502
Other assets	18,615	23,846
Total assets	5,049,325	4,806,159
Accounts payable	443,675	381,795
Short-term debt	0	0
Other Liabilities, Current	117,701	120,299
Total current liabilities	561,376	502,094
Intercompany payables, net	434,019	487,850
Long-term Debt, Excluding Current Maturities	968,361	983,449
Liabilities, Other than Long-term Debt, Noncurrent	61,635	55,898
Total stockholders' equity	3,023,934	2,776,868
Stockholders' Equity Attributable to Noncontrolling Interest	0	0
Total liabilities and stockholders' equity	5,049,325	4,806,159
Non-Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Cash and cash equivalents	48,308	68,579	70,350	121,316
Trade accounts receivable, net	1,236,612	1,034,402
Inventories, net	521,297	456,879
Prepaid Expense and Other Assets, Current	203,991	211,637
Total current assets	2,010,208	1,771,497
Intercompany receivables, net	2,141,945	2,060,336
Property, buildings and equipment, net	107,400	105,783
Intangible assets, net	375,221	389,945
Goodwill and other intangibles, net	1,519,295	1,473,327
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0	0
Other assets	23,064	22,998
Total assets	6,177,133	5,823,886
Accounts payable	394,752	302,926
Short-term debt	39,712	20,920
Other Liabilities, Current	153,033	170,872
Total current liabilities	587,497	494,718
Intercompany payables, net	0	0
Long-term Debt, Excluding Current Maturities	399,940	379,686
Liabilities, Other than Long-term Debt, Noncurrent	171,073	162,641
Total stockholders' equity	5,021,894	4,790,110
Stockholders' Equity Attributable to Noncontrolling Interest	3,271	3,269
Total liabilities and stockholders' equity	6,177,133	5,823,886
Consolidated Entities [Member]
Condensed Financial Information [Line Items]
Cash and cash equivalents	94,083	110,131	112,837	160,279
Trade accounts receivable, net	1,236,612	1,034,402
Inventories, net	925,049	821,441
Prepaid Expense and Other Assets, Current	154,383	137,104
Total current assets	2,410,127	2,103,078
Intercompany receivables, net	0	0
Property, buildings and equipment, net	157,591	157,607
Intangible assets, net	378,153	393,362
Goodwill and other intangibles, net	1,776,918	1,730,950
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0	0
Other assets	41,679	46,844
Total assets	4,764,468	4,431,841
Accounts payable	838,427	684,721
Short-term debt	39,712	20,920
Other Liabilities, Current	165,354	168,158
Total current liabilities	1,043,493	873,799
Intercompany payables, net	0	0
Long-term Debt, Excluding Current Maturities	1,368,301	1,363,135
Liabilities, Other than Long-term Debt, Noncurrent	245,441	231,276
Total stockholders' equity	2,110,504	1,966,900
Stockholders' Equity Attributable to Noncontrolling Interest	3,271	3,269
Total liabilities and stockholders' equity	4,764,468	4,431,841
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	(105,380)	(123,013)
Total current assets	(105,380)	(123,013)
Intercompany receivables, net	(2,141,945)	(2,060,336)
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	(8,045,828)	(7,566,978)
Other assets	0	0
Total assets	(10,293,153)	(9,750,327)
Accounts payable	0	0
Short-term debt	0	0
Other Liabilities, Current	(105,380)	(123,013)
Total current liabilities	(105,380)	(123,013)
Intercompany payables, net	(2,141,945)	(2,060,336)
Long-term Debt, Excluding Current Maturities	0	0
Liabilities, Other than Long-term Debt, Noncurrent	0	0
Total stockholders' equity	(8,045,828)	(7,566,978)
Stockholders' Equity Attributable to Noncontrolling Interest	0	0
Total liabilities and stockholders' equity	$ (10,293,153)	$ (9,750,327)

CONDENSED CONSOLIDATED INCOME S

CONDENSED CONSOLIDATED INCOME STATEMENTS (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Condensed Financial Information [Line Items]
Net sales	$ 2,000,159	$ 1,855,212	$ 5,682,375	$ 5,542,755
Cost of goods sold	1,614,814	1,490,173	4,580,896	4,443,079
Selling, general and administrative expense	280,021	255,547	814,275	799,356
Depreciation and amortization	16,074	16,937	47,758	50,269
Gain (Loss) on Extinguishment of Debt	0	(123,933)	0	(123,933)
Provision for income taxes	18,363	(21,149)	47,684	13,678
Net income (loss)	53,576	(31,021)	140,915	53,367
Less: Net (loss) income attributable to noncontrolling interest	(99)	590	(3)	(876)
Net income (loss) attributable to WESCO International, Inc.	53,675	(31,611)	140,918	54,243
Comprehensive Income:
Foreign currency translation adjustment	51,148	(13,993)	96,097	66,512
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	0	0	252	(16)
Comprehensive income attributable to WESCO International, Inc.	104,823	(45,604)	237,267	120,739
Parent Company [Member]
Condensed Financial Information [Line Items]
Net sales	0	0	0	0
Cost of goods sold	0	0	0	0
Selling, general and administrative expense	0	38	0	(328)
Depreciation and amortization	0	0	0	0
Income (Loss) from Subsidiaries, before Tax	53,576	100,295	140,915	193,266
Interest Income (Expense), Net	0	(4,904)	0	(17,555)
Gain (Loss) on Extinguishment of Debt		123,933		123,933
Provision for income taxes	0	2,441	0	(1,261)
Net income (loss)	53,576	(31,021)	140,915	53,367
Less: Net (loss) income attributable to noncontrolling interest	0	0	0	0
Net income (loss) attributable to WESCO International, Inc.	53,576	(31,021)	140,915	53,367
Comprehensive Income:
Foreign currency translation adjustment	51,148	(13,993)	96,097	66,512
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax			(252)	16
Comprehensive income attributable to WESCO International, Inc.	104,724	(45,014)	237,264	119,863
Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Net sales	867,973	827,648	2,490,102	2,481,165
Cost of goods sold	697,896	663,159	2,002,708	1,985,639
Selling, general and administrative expense	140,638	128,514	410,624	351,663
Depreciation and amortization	4,475	5,114	13,811	15,318
Income (Loss) from Subsidiaries, before Tax	42,726	71,567	117,907	105,401
Interest Income (Expense), Net	(25,436)	(23,543)	(74,961)	(63,247)
Gain (Loss) on Extinguishment of Debt		0		0
Provision for income taxes	(136)	(12,261)	(3,034)	4,677
Net income (loss)	42,390	91,146	108,939	166,022
Less: Net (loss) income attributable to noncontrolling interest	0	0	0	0
Net income (loss) attributable to WESCO International, Inc.	42,390	91,146	108,939	166,022
Comprehensive Income:
Foreign currency translation adjustment	51,148	(13,993)	96,097	66,512
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax			(252)	16
Comprehensive income attributable to WESCO International, Inc.	93,538	77,153	205,288	232,518
Non-Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Net sales	1,169,377	1,052,915	3,289,693	3,140,011
Cost of goods sold	954,109	852,365	2,675,608	2,535,861
Selling, general and administrative expense	139,383	126,995	403,651	448,021
Depreciation and amortization	11,599	11,823	33,947	34,951
Income (Loss) from Subsidiaries, before Tax	0	0	0	0
Interest Income (Expense), Net	(8,125)	(7,655)	(24,114)	(21,729)
Gain (Loss) on Extinguishment of Debt		0		0
Provision for income taxes	18,499	(11,329)	50,718	10,262
Net income (loss)	53,912	80,716	149,883	132,645
Less: Net (loss) income attributable to noncontrolling interest	(99)	590	(3)	(876)
Net income (loss) attributable to WESCO International, Inc.	54,011	80,126	149,886	133,521
Comprehensive Income:
Foreign currency translation adjustment	51,148	(13,993)	96,097	66,512
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax			(252)	16
Comprehensive income attributable to WESCO International, Inc.	105,159	66,133	246,235	200,017
Consolidated Entities [Member]
Condensed Financial Information [Line Items]
Net sales	2,000,159	1,855,212	5,682,375	5,542,755
Cost of goods sold	1,614,814	1,490,173	4,580,896	4,443,079
Selling, general and administrative expense	280,021	255,547	814,275	799,356
Depreciation and amortization	16,074	16,937	47,758	50,269
Income (Loss) from Subsidiaries, before Tax	0	0	0	0
Interest Income (Expense), Net	(17,311)	(20,792)	(50,847)	(59,073)
Gain (Loss) on Extinguishment of Debt		123,933		123,933
Provision for income taxes	18,363	(21,149)	47,684	13,678
Net income (loss)	53,576	(31,021)	140,915	53,367
Less: Net (loss) income attributable to noncontrolling interest	(99)	590	(3)	(876)
Net income (loss) attributable to WESCO International, Inc.	53,675	(31,611)	140,918	54,243
Comprehensive Income:
Foreign currency translation adjustment	51,148	(13,993)	96,097	66,512
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax			(252)	16
Comprehensive income attributable to WESCO International, Inc.	104,823	(45,604)	237,267	120,739
Consolidation, Eliminations [Member]
Condensed Financial Information [Line Items]
Net sales	(37,191)	(25,351)	(97,420)	(78,421)
Cost of goods sold	(37,191)	(25,351)	(97,420)	(78,421)
Selling, general and administrative expense	0	0	0	0
Depreciation and amortization	0	0	0	0
Income (Loss) from Subsidiaries, before Tax	(96,302)	(171,862)	(258,822)	(298,667)
Interest Income (Expense), Net	0	0	0	0
Gain (Loss) on Extinguishment of Debt		0		0
Provision for income taxes	0	0	0	0
Net income (loss)	(96,302)	(171,862)	(258,822)	(298,667)
Less: Net (loss) income attributable to noncontrolling interest	0	0	0	0
Net income (loss) attributable to WESCO International, Inc.	(96,302)	(171,862)	(258,822)	(298,667)
Comprehensive Income:
Foreign currency translation adjustment	(102,296)	27,986	(192,194)	(133,024)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax			504	(32)
Comprehensive income attributable to WESCO International, Inc.	$ (198,598)	$ (143,876)	$ (451,520)	$ (431,659)

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENT OF CASH FLOWS (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	$ 3,490	$ (3,885)
Net cash (used) provided by operating activities	81,111	217,188
Investing Activities:
Capital expenditures	(15,970)	(13,183)
Acquisition payments	0	(50,745)
Net cash used in investing activities	(12,480)	(67,813)
Financing Activities:
Payments for Repurchase of Common Stock	(106,702)	(4,073)
Proceeds from (Payments for) Other Financing Activities	(4,380)	(3,494)
Net cash used in financing activities	(92,164)	(198,085)
Effect of exchange rate changes on cash and cash equivalents	7,485	1,268
Net change in cash and cash equivalents	(16,048)	(47,442)
Cash and cash equivalents at the beginning of period	110,131	160,279
Cash and cash equivalents at the end of period	94,083	112,837
Parent Company [Member]
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	0	0
Net cash (used) provided by operating activities	(28,740)	124,834
Investing Activities:
Capital expenditures	0	0
Acquisition payments		0
Proceeds from Dividends Received	0	0
Net cash used in investing activities	0	0
Financing Activities:
Borrowings	135,442	224,043
Repayments	0	(344,804)
Cash Dividends Paid to Parent Company	0	0
Payments for Repurchase of Common Stock	106,702
Proceeds from (Payments for) Other Financing Activities	0	(4,073)
Net cash used in financing activities	28,740	(124,834)
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	(174,032)	(257,768)
Net cash (used) provided by operating activities	168,603	(274,575)
Investing Activities:
Capital expenditures	(7,435)	(9,224)
Acquisition payments		(50,745)
Proceeds from Dividends Received	51,561	47,621
Net cash used in investing activities	(129,906)	(270,116)
Financing Activities:
Borrowings	557,391	1,386,397
Repayments	(587,485)	(834,688)
Cash Dividends Paid to Parent Company	0	0
Payments for Repurchase of Private Placement	0
Proceeds from (Payments for) Other Financing Activities	(4,380)	(3,494)
Net cash used in financing activities	(34,474)	548,215
Effect of exchange rate changes on cash and cash equivalents	0	0
Net change in cash and cash equivalents	4,223	3,524
Cash and cash equivalents at the beginning of period	41,552	38,963
Cash and cash equivalents at the end of period	45,775	42,487
Non-Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	16,711	(335,594)
Net cash (used) provided by operating activities	(58,752)	366,929
Investing Activities:
Capital expenditures	(8,535)	(3,959)
Acquisition payments		0
Proceeds from Dividends Received	0	0
Net cash used in investing activities	8,176	(339,553)
Financing Activities:
Borrowings	691,682	468,890
Repayments	(617,301)	(500,879)
Cash Dividends Paid to Parent Company	(51,561)	(47,621)
Payments for Repurchase of Common Stock	0
Proceeds from (Payments for) Other Financing Activities	0	0
Net cash used in financing activities	22,820	(79,610)
Effect of exchange rate changes on cash and cash equivalents	7,485	1,268
Net change in cash and cash equivalents	(20,271)	(50,966)
Cash and cash equivalents at the beginning of period	68,579	121,316
Cash and cash equivalents at the end of period	48,308	70,350
Consolidated Entities [Member]
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	3,490	(3,885)
Net cash (used) provided by operating activities	81,111	217,188
Investing Activities:
Capital expenditures	(15,970)	(13,183)
Acquisition payments		(50,745)
Proceeds from Dividends Received	0	0
Net cash used in investing activities	(12,480)	(67,813)
Financing Activities:
Borrowings	1,210,608	1,821,562
Repayments	(1,191,690)	(2,012,080)
Cash Dividends Paid to Parent Company	0	0
Payments for Repurchase of Common Stock	106,702
Proceeds from (Payments for) Other Financing Activities	(4,380)	(7,567)
Net cash used in financing activities	(92,164)	(198,085)
Effect of exchange rate changes on cash and cash equivalents	7,485	1,268
Net change in cash and cash equivalents	(16,048)	(47,442)
Cash and cash equivalents at the beginning of period	110,131	160,279
Cash and cash equivalents at the end of period	94,083	112,837
Consolidation, Eliminations [Member]
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	160,811	589,477
Net cash (used) provided by operating activities	0	0
Investing Activities:
Capital expenditures	0	0
Acquisition payments		0
Proceeds from Dividends Received	(51,561)	(47,621)
Net cash used in investing activities	109,250	541,856
Financing Activities:
Borrowings	(173,907)	(257,768)
Repayments	(13,096)	331,709
Cash Dividends Paid to Parent Company	(51,561)	(47,621)
Payments for Repurchase of Common Stock	0
Proceeds from (Payments for) Other Financing Activities	0	0
Net cash used in financing activities	(109,250)	(541,856)
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	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Goodwill	$ 1,776,918	$ 1,735,662	$ 1,730,950	$ 1,681,662
Goodwill, Foreign Currency Translation Gain (Loss)	45,968	34,799
Goodwill, Purchase Accounting Adjustments	$ 0	$ 19,201