WESCO International (WCC) 10-Q 3 May 19 2019 Q1 Quarterly report Financial data

DOCUMENT AND ENTITY INFORMATION

DOCUMENT AND ENTITY INFORMATION Document - shares	3 Months Ended
	Mar. 31, 2019	May 01, 2019
Entity [Abstract]
Entity Registrant Name	WESCO INTERNATIONAL INC.
Entity Central Index Key	0000929008
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		44,856,784
Entity Current Reporting Status	Yes
Entity Emerging Growth Company	false
Entity Small Business	false

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Depreciation, Depletion and Amortization, Nonproduction	$ 15,242
Other Accrued Liabilities, Current	169,619	$ 105,461
Current Assets:
Cash and cash equivalents	106,100	96,343
Allowance for Doubtful Accounts Receivable, Current	26,828	24,468
Trade accounts receivable, net of allowance for doubtful accounts of $23,069 and $19,309 in 2014 and 2013, respectively	1,268,565	1,166,607
Accounts and Other Receivables, Net, Current	75,326	96,984
Inventories, net	1,001,353	948,726
Prepaid expenses and other current assets	62,406	76,980
Total current assets	2,513,750	2,385,640
Property, buildings and equipment, net of accumulated depreciation of $229,041 and $213,758 in 2014 and 2013, respectively	166,688	160,878
Operating Lease, Right-of-Use Asset	232,989	0
Intangible assets, net	310,453	316,016
Goodwill	1,740,771	1,722,603
Other assets	19,987	19,899
Total assets	4,984,638	4,605,036
Current Liabilities:
Accounts payable	870,242	794,348
Accrued payroll and benefit costs	59,934	88,105
Short-term debt	27,313	30,785
Current portion of long-term debt	1,159	25,429
Total current liabilities	1,150,722	1,061,946
Long-term Debt, Excluding Current Maturities	1,214,276	1,167,311
Operating Lease, Liability, Noncurrent	178,606	0
Other noncurrent liabilities	99,171	102,086
Deferred Tax Liabilities, Net, Noncurrent	145,501	143,967
Total liabilities	2,788,276	2,475,310
Commitments and Contingencies
Bank Overdrafts	22,455	17,818
Stockholders' Equity:
Preferred stock, $.01 par value; 20,000,000 shares authorized, no shares issued or outstanding	0	0
Additional capital	1,015,563	993,666
Retained earnings	2,349,300	2,307,462
Treasury stock, at cost; 18,247,467 and 18,179,275 shares in 2014 and 2013, respectively	(777,216)	(758,018)
Accumulated other comprehensive income	(385,918)	(408,435)
Total WESCO International stockholders' equity	2,196,362	2,129,726
Noncontrolling interest	(6,003)	(5,584)
Total stockholders' equity	2,202,365	2,135,310
Total liabilities and stockholders' equity	4,984,638	4,605,036
Common Stock [Member]
Stockholders' Equity:
Common stock	593	592
Common Class B [Member]
Stockholders' Equity:
Common stock	$ 43	$ 43

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parentheticals) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Allowance for doubtful accounts	$ 26,828,000	$ 24,468,000
Accumulated depreciation	290,883,000	291,811,000
Finite-Lived Intangible Assets, Accumulated Amortization	260,496	249,539
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ 8,508,000	$ 9,243,000
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)	18,756,498	18,391,042
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)	59,271,892	59,157,696
Common stock, shares outstanding (in shares)	44,854,825	45,106,085
Common Class B [Member]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	20,000,000	20,000,000
Common stock, shares, issued (in shares)	4,339,431	4,339,431
Common stock, shares outstanding (in shares)	0	0

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenues	$ 1,961,267	$ 1,993,915
Cost of goods sold	1,578,771	1,613,966
Selling, general and administrative expense	296,528	290,829
Depreciation and amortization	15,242	15,879
Income from operations	70,726	73,241
Nonoperating Income (Expense)	17,120	19,783
Income before income taxes	53,606	53,458
Provision for income taxes	11,656	10,487
Net income	41,950	42,971
Net (loss) income attributable to noncontrolling interest	(419)	(1,450)
Net income attributable to WESCO International, Inc.	42,369	44,421
Comprehensive Income:
Foreign currency translation adjustment	22,517	(28,800)
Comprehensive income attributable to WESCO International, Inc.	$ 64,886	$ 15,621
Earnings per share attributable to WESCO International, Inc.
Basic (in dollars per share)	$ 0.94	$ 0.94
Diluted (in dollars per share)	$ 0.93	$ 0.93
Shipping and Handling [Member]
Cost of goods sold	$ 17,000	$ 18,200

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Cash Flows [Abstract]
Interest Paid, Including Capitalized Interest, Operating and Investing Activities	$ 4,583	$ 4,607
Operating Activities:
Net income	41,950	42,971
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	15,242	15,879
Deferred income taxes	893	2,736
Other operating activities, net	5,961	5,085
Changes in assets and liabilities
Increase (Decrease) in Accounts Receivable	76,696	37,509
Increase (Decrease) in Accounts and Other Receivables	(22,425)	(29,986)
Inventories, net	(40,768)	2,992
Prepaid expenses and other current assets	15,074	4,817
Accounts payable	68,085	8,077
Accrued payroll and benefit costs	(27,851)	(24,561)
Other current and noncurrent liabilities	4,554	2,520
Net cash provided by operating activities	28,869	52,993
Investing Activities:
Payments to Acquire Businesses, Gross	(27,742)	0
Capital expenditures	(10,828)	(7,662)
Other investing activities	53	(8,760)
Net cash used in investing activities	(38,517)	(16,422)
Financing Activities:
Proceeds from issuance of short-term debt	23,569	57,919
Repayments of short-term debt	(51,983)	(52,220)
Proceeds from issuance of long-term debt	423,666	493,000
Repayments of Long-term Debt	(377,825)	(515,000)
Other financing activities, net	(248)	(290)
Net cash used in financing activities	19,246	(28,827)
Payments for Repurchase of Common Stock	(2,572)	(1,661)
Proceeds from (Repayments of) Bank Overdrafts	4,639	(10,575)
Effect of exchange rate on cash and cash equivalents	159	(1,800)
Net change in cash and cash equivalents	9,757	5,944
Cash and cash equivalents at the beginning of period	96,343	117,953
Cash and cash equivalents at the end of period	106,100	123,897
Income Taxes Paid	$ 5,018	$ 5,505

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY Statement - USD ($) $ in Thousands	Total	Common Class B [Member]	Common Stock [Member]	AOCI Attributable to Parent [Member]	Noncontrolling Interest [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Additional Paid-in Capital [Member]
Common Stock, Value, Issued		$ 43	$ 591
Common Stock, Shares, Issued		4,339,431	59,045,762
Additional capital	$ 999,156
Retained Earnings (Accumulated Deficit)	2,079,697
Treasury Stock, Value	$ (647,158)
ERROR in label resolution.	(16,375,653)
Stockholders' Equity Attributable to Noncontrolling Interest	$ (3,596)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(312,590)
Stock Issued, Value, Stock Options Exercised, Net of Tax Benefit (Expense)			$ 0			$ (455)
Adjustments to Additional Paid in Capital, Share-based Compensation and Exercise of Stock Options	(67)
Stock Granted, Value, Share-based Compensation, Net of Forfeitures	3,858
Adjustments Related to Tax Withholding for Share-based Compensation			$ 0				$ 417	$ (1,153)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period			(88,554)			(5,521)
Shares Paid for Tax Withholding for Share Based Compensation			(16,614)
Net Income (Loss) Attributable to Parent	44,421
Net Income (Loss) Attributable to Noncontrolling Interest	(1,450)				$ (1,450)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax				$ (28,800)
Common Stock, Value, Issued		$ 43	$ 591
Common Stock, Shares, Issued		4,339,431	59,117,702
Additional capital	1,001,794
Retained Earnings (Accumulated Deficit)	2,124,535
Treasury Stock, Value	$ (647,613)
ERROR in label resolution.	(16,381,174)
Stockholders' Equity Attributable to Noncontrolling Interest	$ (5,046)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(341,390)
Common Stock, Value, Issued		$ 43	$ 592
Common Stock, Shares, Issued		4,339,431	59,157,696
Additional capital	993,666
Retained Earnings (Accumulated Deficit)	2,307,462
Treasury Stock, Value	$ (758,018)
ERROR in label resolution.	(18,391,042)
Stockholders' Equity Attributable to Noncontrolling Interest	$ (5,584)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(408,435)
Stock Issued, Value, Stock Options Exercised, Net of Tax Benefit (Expense)			$ 1			$ (54)
Adjustments to Additional Paid in Capital, Share-based Compensation and Exercise of Stock Options	(90)
Stock Granted, Value, Share-based Compensation, Net of Forfeitures	4,665
ERROR in label resolution.								19,144
Adjustments Related to Tax Withholding for Share-based Compensation			$ 0				$ (531)	$ (1,822)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period			(156,760)			(184)
Shares Paid for Tax Withholding for Share Based Compensation			(42,564)
Net Income (Loss) Attributable to Parent	42,369
Treasury Stock, Value, Acquired, Cost Method	$ (19,144)
Treasury Stock, Shares, Acquired	(365,272)
Net Income (Loss) Attributable to Noncontrolling Interest	$ (419)				$ (419)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax				$ 22,517
Common Stock, Value, Issued		$ 43	$ 593
Common Stock, Shares, Issued		4,339,431	59,271,892
Additional capital	1,015,563
Retained Earnings (Accumulated Deficit)	2,349,300
Treasury Stock, Value	$ (777,216)
ERROR in label resolution.	(18,756,498)
Stockholders' Equity Attributable to Noncontrolling Interest	$ (6,003)
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (385,918)

ORGANIZATION

ORGANIZATION	3 Months Ended
	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
ORGANIZATION	1. ORGANIZATION WESCO International, Inc. ("WESCO International") and its subsidiaries (collectively, “WESCO” or the "Company"), headquartered in Pittsburgh, Pennsylvania, is a full-line distributor of electrical, industrial and communications maintenance, repair and operating ("MRO") and original equipment manufacturer ("OEM") products, construction materials, and advanced supply chain management and logistics services used primarily in the industrial, construction, utility and commercial, institutional and government markets. WESCO serves approximately 70,000 active customers globally through approximately 500 branches primarily located in North America, with operations in 15 additional countries and 10 distribution centers located in the United States and Canada.

ACCOUNTING POLICIES

ACCOUNTING POLICIES	3 Months Ended
	Mar. 31, 2019
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 2018 Annual Report on Form 10-K as filed with the SEC on February 27, 2019. The Condensed Consolidated Balance Sheet at December 31, 2018 was derived from the audited Consolidated Financial Statements as of that date, but does not include all of the disclosures required by accounting principles generally accepted in the United States of America. The unaudited Condensed Consolidated Balance Sheet as of March 31, 2019 , the unaudited Condensed Consolidated Statements of Income and Comprehensive Income, the unaudited Condensed Consolidated Statements of Cash Flows, and the unaudited Condensed Consolidated Statements of Stockholders' Equity for the three months ended March 31, 2019 and 2018 , respectively, in the opinion of management, have been prepared on the same basis as the audited Consolidated Financial Statements and include all adjustments necessary for the fair statement of the results of the interim periods presented herein. All adjustments reflected in the unaudited condensed consolidated financial information are of a normal recurring nature unless indicated. The results for the interim periods presented herein are not necessarily indicative of the results to be expected for the full year. Recently Adopted Accounting Pronouncements Effective January 1, 2019, WESCO adopted Accounting Standards Update (ASU) 2016-02, Leases , and all the related amendments (“Topic 842”), a comprehensive new standard that amended various aspects of existing accounting guidance for leases. The adoption of Topic 842 resulted in the recognition of right-of-use assets and lease liabilities for operating leases of approximately $240 million and $245 million , respectively, in the Consolidated Balance Sheet as of January 1, 2019, most of which relate to real estate. The adoption of Topic 842 did not have a material impact on the Consolidated Statement of Income and Comprehensive Income or Consolidated Statement of Cash Flow for the three months ended March 31, 2019 . The Company used the optional effective date transition method and therefore did not adjust the prior comparative periods presented herein. There was no cumulative-effect adjustment to beginning retained earnings as a result of using this method. In addition, the Company elected the package of practical expedients that allowed the adoption of Topic 842 without reassessing arrangements that commenced prior to the effective date. Additional qualitative and quantitative information about the Company's leases is disclosed in Note 4. Recently Issued Accounting Pronouncements In June 2016, the Financial Accounting Standards Board (FASB) issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , which introduces new guidance for the accounting for credit losses on certain financial instruments. The amendments in this ASU are effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted. Management does not expect the adoption of this accounting standard to have a material impact on its consolidated financial statements and notes thereto. In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement , which amends the disclosure requirements for recurring and nonrecurring fair value measurements by removing, modifying and adding certain disclosures. The amendments in this ASU are effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. Early adoption is permitted. Management does not expect the adoption of this accounting standard to have a material impact on its consolidated financial statements and notes thereto. In August 2018, the FASB issued ASU 2018-14, Compensation—Retirement Benefits—Defined Benefit Plans—General (Subtopic 715-20): Disclosure Framework—Changes to the Disclosure Requirements for Defined Benefit Plans , which amends the disclosure requirements for all employers that sponsor defined benefit pension and other post retirement plans by removing and adding certain disclosures. The amendments in this ASU are effective for fiscal years ending after December 15, 2020. Early adoption is permitted. Management does not expect the adoption of this accounting standard to have a material impact on its consolidated financial statements and notes thereto. Other pronouncements issued by the FASB or other authoritative accounting standards groups with future effective dates are either not applicable or are not expected to be significant to WESCO’s financial position, results of operations or cash flows.

ACQUISITIONS

ACQUISITIONS	3 Months Ended
	Mar. 31, 2019
Business Combinations [Abstract]
Mergers, Acquisitions and Dispositions Disclosures [Text Block]	5. ACQUISITIONS The following table sets forth the consideration paid for acquisitions: Three Months Ended March 31 2019 (In thousands) Fair value of assets acquired $ 34,812 Fair value of liabilities assumed 7,070 Cash paid for acquisitions $ 27,742 Sylvania Lighting Services Corp. On March 5, 2019 , WESCO Distribution, Inc. ("WESCO Distribution"), through its WESCO Services, LLC subsidiary, acquired certain assets and assumed certain liabilities of Sylvania Lighting Services Corp. ("SLS"). Headquartered in Wilmington, Massachusetts, SLS offers a full spectrum of energy-efficient lighting upgrade, retrofit, and renovation solutions with annual sales of approximately $100 million and approximately 220 employees across the U.S. and Canada. WESCO Distribution funded the purchase price paid at closing with borrowings under its accounts receivable securitization facility. The purchase price was allocated to the respective assets and liabilities based upon their estimated fair values as of the acquisition date, resulting in goodwill of $5.5 million , which is deductible for tax purposes.
ACQUISITIONS	3. REVENUE WESCO distributes products and provides services to customers globally within the following end markets: (1) industrial, (2) construction, (3) utility, and (4) commercial, institutional and government. Revenue is measured as the amount of consideration WESCO expects to receive in exchange for transferring goods or providing services. The following tables disaggregate WESCO’s revenue by end market and geography: Three Months Ended March 31 (In thousands) 2019 2018 Industrial $ 736,906 $ 758,976 Construction 633,288 637,800 Utility 308,269 315,546 Commercial, Institutional and Government 282,804 281,593 Total by end market $ 1,961,267 $ 1,993,915 Three Months Ended March 31 (In thousands) 2019 2018 United States $ 1,460,991 $ 1,482,718 Canada (1) 384,596 398,738 Other International (1) 115,680 112,459 Total by geography $ 1,961,267 $ 1,993,915 (1) The prior period has been reclassified to conform to the current period presentation. In accordance with certain contractual arrangements, WESCO receives payment from its customers in advance and recognizes such payment as deferred revenue. Revenue for advance payment is recognized when the performance obligation has been satisfied and control has transferred to the customer, which is generally upon shipment. Deferred revenue is usually recognized within a year or less from the date of the customer’s advance payment. At March 31, 2019 and December 31, 2018 , $8.8 million and $11.8 million , respectively, of deferred revenue was recorded as a component of other current liabilities in the Condensed Consolidated Balance Sheets. WESCO’s revenues are adjusted for variable consideration, which includes customer volume rebates, returns, and discounts. WESCO measures variable consideration by estimating expected outcomes using analysis and inputs based upon anticipated performance, historical data, as well as current and forecasted information. Measurement and recognition of variable consideration is reviewed by management on a monthly basis and revenue is adjusted accordingly. Variable consideration reduced revenue for the three months ended March 31, 2019 and 2018 by approximately $25.5 million and $23.8 million , respectively. Shipping and handling costs are recognized in net sales when they are billed to the customer. These costs are recognized as a component of selling, general and administrative expenses when WESCO does not bill the customer. WESCO has elected to recognize shipping and handling costs as a fulfillment cost. Shipping and handling costs recorded as a component of selling, general and administrative expenses totaled $17.0 million and $18.2 million for the three months ended March 31, 2019 and 2018 , respectively.

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	3 Months Ended
	Mar. 31, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
STOCK-BASED COMPENSATION	. STOCK-BASED COMPENSATION WESCO’s stock-based employee compensation plans are comprised of stock-settled stock appreciation rights, restricted stock units and performance-based awards. Compensation cost for all stock-based awards is measured at fair value on the date of grant and compensation cost is recognized, net of estimated forfeitures, over the service period for awards expected to vest. The fair value of stock-settled stock appreciation rights and performance-based awards with market conditions is determined using the Black-Scholes and Monte Carlo simulation models, respectively. The fair value of restricted stock units and performance-based awards with performance conditions is determined by the grant-date closing price of WESCO’s common stock. The forfeiture assumption is based on WESCO’s historical employee behavior that is reviewed on an annual basis. No dividends are assumed. For stock-settled stock appreciation rights that are exercised and for restricted stock units and performance-based award that vest, shares are issued out of WESCO's outstanding common stock. Stock-settled stock appreciation rights vest ratably over a three-year period and terminate on the tenth anniversary of the grant date unless terminated sooner under certain conditions. Vesting of restricted stock units is based on a minimum time period of three years. Vesting of performance-based awards is based on a three-year performance period, and the number of shares earned, if any, depends on the attainment of certain performance levels. Outstanding awards would vest upon the consummation of a change in control transaction and performance-based awards would vest at the target level. Performance-based awards granted in 2019 were based on two equally-weighted performance measures, which include the three-year average growth rate of WESCO's net income and the three-year cumulative return on net assets. Performance-based awards granted in 2018 were based on two equally-weighted performance measures, which include the three-year average growth rate of the Company’s fully diluted earnings per share and the three-year cumulative return on net assets. From 2015 to 2017, the two equally-weighted performance-based award metrics were the three-year average growth rate of WESCO's net income and WESCO's total stockholder return in relation to the total stockholder return of a select group of peer companies over a three-year period. During the three months ended March 31, 2019 and 2018 , WESCO granted the following stock-settled stock appreciation rights, restricted stock units and performance-based awards at the following weighted-average fair values: Three Months Ended March 31, March 31, Stock-settled stock appreciation rights granted 213,618 491,229 Weighted-average fair value $ 16.36 $ 18.40 Restricted stock units granted 175,544 114,269 Weighted-average fair value $ 54.64 $ 62.81 Performance-based awards granted 126,874 44,144 Weighted-average fair value $ 54.64 $ 62.80 The fair value of stock-settled stock appreciation rights was estimated using the following weighted-average assumptions: Three Months Ended March 31, March 31, Risk free interest rate 2.5 % 2.5 % Expected life (in years) 5 5 Expected volatility 29 % 28 % The risk-free interest rate is based on the U.S. Treasury Daily Yield Curve as of the grant date. The expected life is based on historical exercise experience and the expected volatility is based on the volatility of the Company's daily stock prices over a five-year period preceding the grant date. The following table sets forth a summary of stock-settled stock appreciation rights and related information for the three months ended March 31, 2019 : Awards Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (In years) Aggregate Intrinsic Value (In thousands) Outstanding at December 31, 2018 2,351,633 $ 59.26 Granted 213,618 54.63 Exercised (51,635 ) 35.11 Forfeited (26,236 ) 70.00 Outstanding at March 31, 2019 2,487,380 59.25 6.3 $ 9,222 Exercisable at March 31, 2019 1,815,662 $ 58.38 5.3 $ 9,217 The following table sets forth a summary of time-based restricted stock units and related information for the three months ended March 31, 2019 : Awards Weighted- Average Fair Value Unvested at December 31, 2018 327,798 $ 57.87 Granted 175,544 54.64 Vested (112,500 ) 43.58 Forfeited (1,565 ) 57.49 Unvested at March 31, 2019 389,277 $ 60.48 Performance shares are awards for which the vesting will occur based on market or performance conditions. The following table sets forth a summary of performance-based awards for the three months ended March 31, 2019 : Awards Weighted- Average Fair Value Unvested at December 31, 2018 138,896 $ 59.33 Granted 126,874 54.64 Vested (25,696 ) 42.44 Forfeited (35,486 ) 50.79 Unvested at March 31, 2019 204,588 $ 60.11 The unvested performance-based awards in the table above include 17,507 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 187,081 shares of performance-based awards in the table above is dependent upon the achievement of certain performance targets, including 80,944 that are dependent upon the three-year average growth rate of WESCO's net income, 21,350 that are dependent upon the three-year average growth rate of the Company's fully diluted earnings per share, and 84,787 that are based upon the three-year cumulative return on net assets. These awards are accounted for as awards with performance conditions; compensation cost is recognized over the performance period based upon WESCO's determination of whether it is probable that the performance targets will be achieved. WESCO recognized $4.7 million and $3.9 million of non-cash stock-based compensation expense, which is included in selling, general and administrative expenses, for the three months ended March 31, 2019 and 2018 , respectively. As of March 31, 2019 , there was $36.6 million of total unrecognized compensation cost related to non-vested stock-based compensation arrangements for all awards previously made, of which approximately $15.4 million is expected to be recognized over the remainder of 2019 , $13.5 million in 2020 , $7.0 million in 2021 and $0.7 million in 2022 .

EARNINGS PER SHARE

EARNINGS PER SHARE	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
EARNINGS PER SHARE	8. EARNINGS PER SHARE Basic earnings per share is computed by dividing net income attributable to WESCO International by the weighted-average number of common shares outstanding during the periods. Diluted earnings per share is computed by dividing net income attributable to WESCO International by the weighted-average common shares and common share equivalents outstanding during the periods. The dilutive effect of common share equivalents is considered in the diluted earnings per share computation using the treasury stock method, which includes consideration of equity awards. The following table sets forth the details of basic and diluted earnings per share: Three Months Ended March 31 (In thousands, except per share data) 2019 2018 Net income attributable to WESCO International $ 42,369 $ 44,421 Weighted-average common shares outstanding used in computing basic earnings per share 45,076 47,038 Common shares issuable upon exercise of dilutive equity awards 415 570 Weighted-average common shares outstanding and common share equivalents used in computing diluted earnings per share 45,491 47,608 Earnings per share attributable to WESCO International Basic $ 0.94 $ 0.94 Diluted $ 0.93 $ 0.93 For the three months ended March 31, 2019 and 2018 , the computation of diluted earnings per share attributable to WESCO International excluded stock-based awards of approximately 1.8 million and 1.5 million , respectively. These amounts were excluded because their effect would have been antidilutive. In December 2017, the Company's Board of Directors authorized the repurchase of up to $300 million of the Company's common stock through December 31, 2020 . In October 2018, the Board approved an increase to this repurchase authorization from $300 million to $400 million . On November 6, 2018 , 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 $100.0 million , the Company received a total of 1,953,167 shares, 365,272 of which were received during the three months ended March 31, 2019 . WESCO funded the repurchase with borrowings under its accounts receivable securitization and revolving credit facilities. The total number of shares ultimately delivered under the ASR Transaction was determined by the average of the volume-weighted average price of the Company's common stock for each exchange business day during the settlement valuation period. For purposes of computing earnings per share for the three months ended March 31, 2019 , shares received under the ASR Transaction were reflected as a reduction to common shares outstanding on the respective delivery dates.

EMPLOYEE BENEFIT PLANS

EMPLOYEE BENEFIT PLANS	3 Months Ended
	Mar. 31, 2019
Retirement Benefits [Abstract]
EMPLOYEE BENEFIT PLANS	9. EMPLOYEE BENEFIT PLANS A majority of WESCO’s employees are covered by defined contribution retirement savings plans for their services rendered subsequent to WESCO’s formation. WESCO also offers a deferred compensation plan for select individuals. For U.S. participants, WESCO matches contributions made by employees at an amount equal to 50% of participants' total monthly contributions up to a maximum of 6% of eligible compensation. For Canadian participants, WESCO makes contributions in amounts ranging from 3% to 5% of participants' eligible compensation based on years of continuous service. WESCO may also make, subject to the Board of Directors' approval, a discretionary contribution to the defined contribution retirement savings plan covering U.S. participants if certain predetermined profit levels are attained. For the three months ended March 31, 2019 and 2018 , WESCO incurred charges of $12.6 million and $10.7 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 March 31, 2019 and December 31, 2018 , the Company's obligation under the deferred compensation plan was $23.1 million and $21.9 million , respectively. Employees have the option to transfer balances allocated to their accounts in the defined contribution retirement savings plan and the deferred compensation plan into any of the available investment options. The Company sponsors a contributory defined benefit plan covering substantially all Canadian employees of EECOL and a Supplemental Executive Retirement Plan (the "SERP") for certain executives of EECOL. During the three months ended March 31, 2019 , the Company contributed $0.1 million to the SERP. The following table sets forth the components of net periodic benefit costs for the defined benefit plans: Three Months Ended March 31 (In thousands) 2019 2018 Service cost $ 1,149 $ 1,347 Interest cost 1,089 1,066 Expected return on plan assets (1,422 ) (1,540 ) Recognized actuarial gain (16 ) (12 ) Net periodic benefit cost $ 800 $ 861 The service cost of $1.1 million and $1.3 million for the three months ended March 31, 2019 and 2018 was reported as a component of selling, general and administrative expenses. The other components of net periodic benefit cost totaling a net benefit of $0.3 million and $0.5 million for the three months ended March 31, 2019 and 2018 were presented as a component of net interest and other.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	3 Months Ended
	Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	11. COMMITMENTS AND CONTINGENCIES From time to time, a number of lawsuits and claims have been or may be asserted against the Company relating to the conduct of its business, including litigation relating to commercial, product and employment matters. The outcome of any litigation cannot be predicted with certainty, and some lawsuits may be determined adversely to WESCO. However, management does not believe that the ultimate outcome of any such pending matters is likely to have a material adverse effect on WESCO's financial condition or liquidity, although the resolution in any fiscal period of one or more of these matters may have a material adverse effect on WESCO's results of operations for that period. In an effort to expand the Company's footprint in the Middle East, WESCO has been doing business since 2009 with WESTEC Supplies General Trading (“WESTEC”), an industrial equipment supplier headquartered in the United Arab Emirates. WESTEC has a line of credit with a maximum borrowing capacity of approximately $6.8 million to support its working capital requirements and joint sales efforts with WESCO. Due to the nature of WESCO’s arrangement with WESTEC, WESCO has provided a standby letter of credit under its revolving credit facility of up to $7.3 million as security for WESTEC’s line of credit. As of March 31, 2019 , WESTEC had an outstanding loan balance of $6.5 million . Management currently believes the estimated fair value of the noncontingent guarantee on the line of credit is nominal and therefore a liability has not been recorded as of March 31, 2019 .

INCOME TAXES

INCOME TAXES	3 Months Ended
	Mar. 31, 2019
Income Tax Disclosure [Abstract]
INCOME TAXES	12. INCOME TAXES The effective tax rate for the three months ended March 31, 2019 and 2018 was 21.7% and 19.6% , respectively. WESCO’s effective tax rate is typically impacted by the tax effect of intercompany financing, foreign tax rate differences, nondeductible expenses and state income taxes. The higher effective tax rate for the three months ended March 31, 2019 was primarily due to the full application of the international provisions of U.S. tax reform. There have been no material adjustments to liabilities for uncertain tax positions since the last annual disclosure for the year ended December 31, 2018 .

OTHER FINANCIAL INFORMATION

OTHER FINANCIAL INFORMATION	3 Months Ended
	Mar. 31, 2019
Condensed Financial Information [Abstract]
OTHER FINANCIAL INFORMATION	13. 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 March 31, 2019 (In thousands) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Cash and cash equivalents $ — $ 38,774 $ 67,326 $ — $ 106,100 Trade accounts receivable, net — — 1,268,565 — 1,268,565 Inventories — 453,738 547,615 — 1,001,353 Prepaid expenses and other current assets 1,127 22,341 118,406 (4,142 ) 137,732 Total current assets 1,127 514,853 2,001,912 (4,142 ) 2,513,750 Intercompany receivables, net — — 2,400,124 (2,400,124 ) — Property, buildings and equipment, net — 68,829 97,859 — 166,688 Operating lease assets — 139,397 93,592 — 232,989 Intangible assets, net — 1,974 308,479 — 310,453 Goodwill — 257,623 1,483,148 — 1,740,771 Investments in affiliates 3,252,590 5,202,712 — (8,455,302 ) — Other assets — 2,717 17,270 — 19,987 Total assets $ 3,253,717 $ 6,188,105 $ 6,402,384 $ (10,859,568 ) $ 4,984,638 Accounts payable $ — $ 426,015 $ 444,227 $ — $ 870,242 Short-term debt — — 27,313 — 27,313 Other current liabilities — 82,527 174,782 (4,142 ) 253,167 Total current liabilities — 508,542 646,322 (4,142 ) 1,150,722 Intercompany payables, net 1,051,352 1,348,772 — (2,400,124 ) — Long-term debt, net — 841,554 372,722 — 1,214,276 Operating lease liabilities — 110,998 67,608 — 178,606 Other noncurrent liabilities — 125,649 119,023 — 244,672 Total WESCO International stockholders' equity 2,202,365 3,252,590 5,202,712 (8,455,302 ) 2,202,365 Noncontrolling interests — — (6,003 ) — (6,003 ) Total liabilities and stockholders’ equity $ 3,253,717 $ 6,188,105 $ 6,402,384 $ (10,859,568 ) $ 4,984,638 Condensed Consolidating Balance Sheet December 31, 2018 (In thousands) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Cash and cash equivalents $ — $ 35,931 $ 60,412 $ — $ 96,343 Trade accounts receivable, net — — 1,166,607 — 1,166,607 Inventories — 440,422 508,304 — 948,726 Prepaid expenses and other current assets 1,123 57,586 124,523 (9,268 ) 173,964 Total current assets 1,123 533,939 1,859,846 (9,268 ) 2,385,640 Intercompany receivables, net — — 2,403,704 (2,403,704 ) — Property, buildings and equipment, net — 63,506 97,372 — 160,878 Intangible assets, net — 2,131 313,885 — 316,016 Goodwill — 257,623 1,464,980 — 1,722,603 Investments in affiliates 3,182,469 5,137,783 — (8,320,252 ) — Other assets — 2,905 16,994 — 19,899 Total assets $ 3,183,592 $ 5,997,887 $ 6,156,781 $ (10,733,224 ) $ 4,605,036 Accounts payable $ — $ 404,373 $ 389,975 $ — $ 794,348 Short-term debt — — 30,785 — 30,785 Other current liabilities — 86,600 159,481 (9,268 ) 236,813 Total current liabilities — 490,973 580,241 (9,268 ) 1,061,946 Intercompany payables, net 1,048,282 1,355,422 — (2,403,704 ) — Long-term debt, net — 842,093 325,218 — 1,167,311 Other noncurrent liabilities — 126,930 119,123 — 246,053 Total WESCO International stockholders' equity 2,135,310 3,182,469 5,137,783 (8,320,252 ) 2,135,310 Noncontrolling interests — — (5,584 ) — (5,584 ) Total liabilities and stockholders’ equity $ 3,183,592 $ 5,997,887 $ 6,156,781 $ (10,733,224 ) $ 4,605,036 Condensed Consolidating Statement of Income and Comprehensive Income Three Months Ended March 31, 2019 (In thousands) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 857,982 $ 1,142,394 $ (39,109 ) $ 1,961,267 Cost of goods sold (excluding depreciation and amortization) — 689,556 928,324 (39,109 ) 1,578,771 Selling, general and administrative expenses — 152,429 144,099 — 296,528 Depreciation and amortization — 4,555 10,687 — 15,242 Results of affiliates’ operations 41,950 42,413 — (84,363 ) — Net interest and other — 12,034 5,086 — 17,120 Income tax expense — (129 ) 11,785 — 11,656 Net income 41,950 41,950 42,413 (84,363 ) 41,950 Net loss attributable to noncontrolling interests — — (419 ) — (419 ) Net income attributable to WESCO International $ 41,950 $ 41,950 $ 42,832 $ (84,363 ) $ 42,369 Other comprehensive loss: Foreign currency translation adjustments 22,517 22,517 22,517 (45,034 ) 22,517 Comprehensive income attributable to WESCO International $ 64,467 $ 64,467 $ 65,349 $ (129,397 ) $ 64,886 Condensed Consolidating Statement of Income and Comprehensive Income Three Months Ended March 31, 2018 (In thousands) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 882,399 $ 1,150,110 $ (38,594 ) $ 1,993,915 Cost of goods sold (excluding depreciation and amortization) — 716,258 936,302 (38,594 ) 1,613,966 Selling, general and administrative expenses — 150,482 140,347 — 290,829 Depreciation and amortization — 4,616 11,263 — 15,879 Results of affiliates’ operations 42,971 45,200 — (88,171 ) — Net interest and other — 13,816 5,967 — 19,783 Income tax (benefit) expense — (544 ) 11,031 — 10,487 Net income 42,971 42,971 45,200 (88,171 ) 42,971 Net loss attributable to noncontrolling interests — — (1,450 ) — (1,450 ) Net income attributable to WESCO International $ 42,971 $ 42,971 $ 46,650 $ (88,171 ) $ 44,421 Other comprehensive loss: Foreign currency translation adjustments (28,800 ) (28,800 ) (28,800 ) 57,600 (28,800 ) Comprehensive income attributable to WESCO International $ 14,171 $ 14,171 $ 17,850 $ (30,571 ) $ 15,621 Condensed Consolidating Statement of Cash Flows Three Months Ended March 31, 2019 (In thousands) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net cash (used in) provided by operating activities $ 5,157 $ 27,122 $ (3,410 ) $ — $ 28,869 Investing activities: Acquisition payments — (27,742 ) — — (27,742 ) Capital expenditures — (2,513 ) (8,315 ) — (10,828 ) Dividends received from subsidiaries — 22,095 — (22,095 ) — Other — (19,510 ) 53 19,510 53 Net cash used in investing activities — (27,670 ) (8,262 ) (2,585 ) (38,517 ) Financing activities: Borrowings — 139,134 330,196 (22,095 ) 447,235 Repayments (2,585 ) (140,134 ) (289,674 ) 2,585 (429,808 ) Repurchases of common stock (2,572 ) — — — (2,572 ) Dividends paid by subsidiaries — — (22,095 ) 22,095 — Increase in bank overdrafts — 4,639 — — 4,639 Other — (248 ) — — (248 ) Net cash provided by (used in) financing activities (5,157 ) 3,391 18,427 2,585 19,246 Effect of exchange rate changes on cash and cash equivalents — — 159 — 159 Net change in cash and cash equivalents — 2,843 6,914 — 9,757 Cash and cash equivalents at the beginning of period — 35,931 60,412 — 96,343 Cash and cash equivalents at the end of period $ — $ 38,774 $ 67,326 $ — $ 106,100 Condensed Consolidating Statement of Cash Flows Three Months Ended March 31, 2018 (In thousands) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net cash provided by (used in) operating activities $ 5,497 $ 57,694 $ (10,198 ) $ — $ 52,993 Investing activities: Capital expenditures — (2,954 ) (4,708 ) — (7,662 ) Dividends received from subsidiaries — 22,744 — (22,744 ) — Other — (18,908 ) (8,760 ) 18,908 (8,760 ) Net cash provided by (used in) investing activities — 882 (13,468 ) (3,836 ) (16,422 ) Financing activities: Borrowings — 58,000 515,663 (22,744 ) 550,919 Repayments (3,836 ) (90,000 ) (477,220 ) 3,836 (567,220 ) Repurchases of common stock (1,661 ) — — — (1,661 ) Dividends paid by subsidiaries — — (22,744 ) 22,744 — Decrease in bank overdrafts — (10,575 ) — — (10,575 ) Other — (290 ) — — (290 ) Net cash (used in) provided by financing activities (5,497 ) (42,865 ) 15,699 3,836 (28,827 ) Effect of exchange rate changes on cash and cash equivalents — — (1,800 ) — (1,800 ) Net change in cash and cash equivalents — 15,711 (9,767 ) — 5,944 Cash and cash equivalents at the beginning of period — 50,602 67,351 — 117,953 Cash and cash equivalents at the end of period $ — $ 66,313 $ 57,584 $ — $ 123,897

Subsequent Events SUBSEQUENT EV

Subsequent Events SUBSEQUENT EVENTS (Notes)	3 Months Ended
	Mar. 31, 2019
Subsequent Events [Abstract]
Subsequent Events [Text Block]	14. 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)	3 Months Ended
	Mar. 31, 2019
Goodwill [Line Items]
Goodwill Disclosure [Text Block]	6. GOODWILL The following table sets forth the changes in the carrying value of goodwill: Three Months Ended March 31 (In thousands) 2019 Beginning balance January 1 $ 1,722,603 Foreign currency exchange rate changes 12,642 Additions to goodwill for acquisitions 5,526 Ending balance March 31 $ 1,740,771

NET INTEREST AND OTHER (Notes)

NET INTEREST AND OTHER (Notes)	3 Months Ended
	Mar. 31, 2019
Other Income and Expenses [Abstract]
Other Nonoperating Income and Expense [Text Block]	10. FAIR VALUE OF FINANCIAL INSTRUMENTS The Company’s financial instruments consist of cash and cash equivalents, accounts receivable, accounts payable, bank overdrafts, and outstanding indebtedness. The Company uses a market approach to determine the fair value of its debt instruments, utilizing quoted prices in active markets, interest rates and other relevant information generated by market transactions involving similar instruments. Therefore, the inputs used to measure the fair value of the Company's debt instruments are classified as Level 2 within the fair value hierarchy. The reported carrying amounts of WESCO's financial instruments approximated their fair values as of March 31, 2019 and December 31, 2018 .

LEASES (Notes)

LEASES (Notes)	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Leases of Lessee Disclosure [Text Block]	4. LEASES WESCO leases real estate, automobiles, trucks and other equipment. The determination of whether an arrangement is, or contains, a lease is performed at the inception of the arrangement. Classification and initial measurement of the right-of-use asset and lease liability are determined at the lease commencement date. The Company has elected the short-term lease measurement and recognition exemption; therefore, leases with an initial term of 12 months or less are not recorded on the balance sheet. The Company's arrangements include certain non-lease components such as common area and other maintenance for leased real estate, as well as mileage, fuel and maintenance costs related to its leased automobiles and trucks. WESCO accounts for these nonlease components separately from the associated lease components. The Company does not guarantee any residual value in its lease agreements, and there are no material restrictions or covenants imposed by lease arrangements. Real estate leases typically include one or more options to extend the lease. The Company regularly evaluates the renewal options, and when they are reasonably certain of exercise, the Company includes the renewal period in its lease term. The Company uses the interest rate implicit in its leases to discount lease payments at the lease commencement date. When the implicit rate is not readily available, the Company uses its incremental borrowing rate. The Company's finance leases, which are recorded in the Condensed Consolidated Balance Sheet as of March 31, 2019 as a component of property, buildings and equipment, current portion of long-term debt and long-term debt, respectively, are not material to the consolidated financial statements and notes thereto. Accordingly, finance leases have not been disclosed herein. The following table sets forth supplemental balance sheet information related to operating leases for the period presented: As of (In thousands) March 31, 2019 Operating lease assets $ 232,989 Current operating lease liabilities 59,236 Noncurrent operating lease liabilities 178,606 Total operating lease liabilities $ 237,842 The following table sets forth the Company's total lease cost, which is recorded as a component of selling, general and administrative expenses, for the period presented: Three Months Ended March 31 (In thousands) 2019 Operating lease cost $ 18,003 Short-term lease cost 11 Variable lease cost 5,321 Total lease cost $ 23,335 Variable lease cost consists of the non-lease components described above, as well as taxes and insurance for WESCO's leased real estate. The following table sets forth supplemental cash flow information related to operating leases for the period presented: Three Months Ended March 31 (In thousands) 2019 Operating cash flows from operating leases $ 18,012 Right-of-use assets obtained in exchange for new operating lease liabilities 8,092 For the three months ended March 31, 2019 , the weighted-average remaining lease term for operating leases was 5.5 years and the weighted-average discount rate used to measure operating lease assets and liabilities was 4.6% . The following table sets forth the maturities of the Company's operating lease liabilities and reconciles the respective undiscounted payments to the operating lease liabilities in the Condensed Consolidated Balance Sheet as of March 31, 2019 : (In thousands) 2019 $ 59,033 2020 61,233 2021 49,587 2022 36,767 2023 27,547 Thereafter 45,701 Total undiscounted operating lease payments 279,868 Less: interest (42,026 ) Total operating lease liabilities $ 237,842 The following table sets forth the future minimum rental payments for operating leases accounted for in accordance with Accounting Standards Codification Topic 840, Leases , as of December 31, 2018 : Years ending December 31 (In thousands) 2019 $ 71,640 2020 59,594 2021 47,264 2022 34,490 2023 24,493 Thereafter 40,302

ACCOUNTING POLICIES (Policies)

ACCOUNTING POLICIES (Policies)	3 Months Ended
	Mar. 31, 2019
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 2018 Annual Report on Form 10-K as filed with the SEC on February 27, 2019. The Condensed Consolidated Balance Sheet at December 31, 2018 was derived from the audited Consolidated Financial Statements as of that date, but does not include all of the disclosures required by accounting principles generally accepted in the United States of America. The unaudited Condensed Consolidated Balance Sheet as of March 31, 2019 , the unaudited Condensed Consolidated Statements of Income and Comprehensive Income, the unaudited Condensed Consolidated Statements of Cash Flows, and the unaudited Condensed Consolidated Statements of Stockholders' Equity for the three months ended March 31, 2019 and 2018 , 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.
New Accounting Pronouncements and Changes in Accounting Principles [Text Block]	Recently Adopted Accounting Pronouncements Effective January 1, 2019, WESCO adopted Accounting Standards Update (ASU) 2016-02, Leases , and all the related amendments (“Topic 842”), a comprehensive new standard that amended various aspects of existing accounting guidance for leases. The adoption of Topic 842 resulted in the recognition of right-of-use assets and lease liabilities for operating leases of approximately $240 million and $245 million , respectively, in the Consolidated Balance Sheet as of January 1, 2019, most of which relate to real estate. The adoption of Topic 842 did not have a material impact on the Consolidated Statement of Income and Comprehensive Income or Consolidated Statement of Cash Flow for the three months ended March 31, 2019 . The Company used the optional effective date transition method and therefore did not adjust the prior comparative periods presented herein. There was no cumulative-effect adjustment to beginning retained earnings as a result of using this method. In addition, the Company elected the package of practical expedients that allowed the adoption of Topic 842 without reassessing arrangements that commenced prior to the effective date. Additional qualitative and quantitative information about the Company's leases is disclosed in Note 4.
Fair Value of Financial Instruments	10. FAIR VALUE OF FINANCIAL INSTRUMENTS The Company’s financial instruments consist of cash and cash equivalents, accounts receivable, accounts payable, bank overdrafts, and outstanding indebtedness. The Company uses a market approach to determine the fair value of its debt instruments, utilizing quoted prices in active markets, interest rates and other relevant information generated by market transactions involving similar instruments. Therefore, the inputs used to measure the fair value of the Company's debt instruments are classified as Level 2 within the fair value hierarchy. The reported carrying amounts of WESCO's financial instruments approximated their fair values as of March 31, 2019 and December 31, 2018 .
New Accounting Pronouncements, Policy [Policy Text Block]	Recently Issued Accounting Pronouncements In June 2016, the Financial Accounting Standards Board (FASB) issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , which introduces new guidance for the accounting for credit losses on certain financial instruments. The amendments in this ASU are effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted. Management does not expect the adoption of this accounting standard to have a material impact on its consolidated financial statements and notes thereto. In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement , which amends the disclosure requirements for recurring and nonrecurring fair value measurements by removing, modifying and adding certain disclosures. The amendments in this ASU are effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. Early adoption is permitted. Management does not expect the adoption of this accounting standard to have a material impact on its consolidated financial statements and notes thereto. In August 2018, the FASB issued ASU 2018-14, Compensation—Retirement Benefits—Defined Benefit Plans—General (Subtopic 715-20): Disclosure Framework—Changes to the Disclosure Requirements for Defined Benefit Plans , which amends the disclosure requirements for all employers that sponsor defined benefit pension and other post retirement plans by removing and adding certain disclosures. The amendments in this ASU are effective for fiscal years ending after December 15, 2020. Early adoption is permitted. Management does not expect the adoption of this accounting standard to have a material impact on its consolidated financial statements and notes thereto. Other pronouncements issued by the FASB or other authoritative accounting standards groups with future effective dates are either not applicable or are not expected to be significant to WESCO’s financial position, results of operations or cash flows.

ACQUISITIONS (Tables)

ACQUISITIONS (Tables)	3 Months Ended
	Mar. 31, 2019
Acquisitions [Abstract]
Schedule of Business Acquisitions, by Acquisition [Table Text Block]	Three Months Ended March 31 2019 (In thousands) Fair value of assets acquired $ 34,812 Fair value of liabilities assumed 7,070 Cash paid for acquisitions $ 27,742

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	3 Months Ended
	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]	During the three months ended March 31, 2019 and 2018 , WESCO granted the following stock-settled stock appreciation rights, restricted stock units and performance-based awards at the following weighted-average fair values: Three Months Ended March 31, March 31, Stock-settled stock appreciation rights granted 213,618 491,229 Weighted-average fair value $ 16.36 $ 18.40 Restricted stock units granted 175,544 114,269 Weighted-average fair value $ 54.64 $ 62.81 Performance-based awards granted 126,874 44,144 Weighted-average fair value $ 54.64 $ 62.80
Schedule of Share-based Compensation, Stock Options and Stock Appreciation Rights Award Activity [Table Text Block]	The following table sets forth a summary of stock-settled stock appreciation rights and related information for the three months ended March 31, 2019 : Awards Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (In years) Aggregate Intrinsic Value (In thousands) Outstanding at December 31, 2018 2,351,633 $ 59.26 Granted 213,618 54.63 Exercised (51,635 ) 35.11 Forfeited (26,236 ) 70.00 Outstanding at March 31, 2019 2,487,380 59.25 6.3 $ 9,222 Exercisable at March 31, 2019 1,815,662 $ 58.38 5.3 $ 9,217
Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block]	The following table sets forth a summary of time-based restricted stock units and related information for the three months ended March 31, 2019 : Awards Weighted- Average Fair Value Unvested at December 31, 2018 327,798 $ 57.87 Granted 175,544 54.64 Vested (112,500 ) 43.58 Forfeited (1,565 ) 57.49 Unvested at March 31, 2019 389,277 $ 60.48
Schedule of Nonvested Performance-based Units Activity [Table Text Block]	The following table sets forth a summary of performance-based awards for the three months ended March 31, 2019 : Awards Weighted- Average Fair Value Unvested at December 31, 2018 138,896 $ 59.33 Granted 126,874 54.64 Vested (25,696 ) 42.44 Forfeited (35,486 ) 50.79 Unvested at March 31, 2019 204,588 $ 60.11
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 March 31, March 31, Risk free interest rate 2.5 % 2.5 % Expected life (in years) 5 5 Expected volatility 29 % 28 %
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]

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]	The following table sets forth the details of basic and diluted earnings per share: Three Months Ended March 31 (In thousands, except per share data) 2019 2018 Net income attributable to WESCO International $ 42,369 $ 44,421 Weighted-average common shares outstanding used in computing basic earnings per share 45,076 47,038 Common shares issuable upon exercise of dilutive equity awards 415 570 Weighted-average common shares outstanding and common share equivalents used in computing diluted earnings per share 45,491 47,608 Earnings per share attributable to WESCO International Basic $ 0.94 $ 0.94 Diluted $ 0.93 $ 0.93

EMPLOYEE BENEFIT PLANS Schedule

EMPLOYEE BENEFIT PLANS Schedule of Net Benefit Costs (Tables)	3 Months Ended
	Mar. 31, 2019
Postemployment Benefits [Abstract]
Schedule of Net Benefit Costs [Table Text Block]	The following table sets forth the components of net periodic benefit costs for the defined benefit plans: Three Months Ended March 31 (In thousands) 2019 2018 Service cost $ 1,149 $ 1,347 Interest cost 1,089 1,066 Expected return on plan assets (1,422 ) (1,540 ) Recognized actuarial gain (16 ) (12 ) Net periodic benefit cost $ 800 $ 861

OTHER FINANCIAL INFORMATION (Ta

OTHER FINANCIAL INFORMATION (Tables)	3 Months Ended
	Mar. 31, 2019
Condensed Balance Sheet Statements, Captions [Line Items]
Condensed Balance Sheet [Table Text Block]	Condensed Consolidating Balance Sheet March 31, 2019 (In thousands) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Cash and cash equivalents $ — $ 38,774 $ 67,326 $ — $ 106,100 Trade accounts receivable, net — — 1,268,565 — 1,268,565 Inventories — 453,738 547,615 — 1,001,353 Prepaid expenses and other current assets 1,127 22,341 118,406 (4,142 ) 137,732 Total current assets 1,127 514,853 2,001,912 (4,142 ) 2,513,750 Intercompany receivables, net — — 2,400,124 (2,400,124 ) — Property, buildings and equipment, net — 68,829 97,859 — 166,688 Operating lease assets — 139,397 93,592 — 232,989 Intangible assets, net — 1,974 308,479 — 310,453 Goodwill — 257,623 1,483,148 — 1,740,771 Investments in affiliates 3,252,590 5,202,712 — (8,455,302 ) — Other assets — 2,717 17,270 — 19,987 Total assets $ 3,253,717 $ 6,188,105 $ 6,402,384 $ (10,859,568 ) $ 4,984,638 Accounts payable $ — $ 426,015 $ 444,227 $ — $ 870,242 Short-term debt — — 27,313 — 27,313 Other current liabilities — 82,527 174,782 (4,142 ) 253,167 Total current liabilities — 508,542 646,322 (4,142 ) 1,150,722 Intercompany payables, net 1,051,352 1,348,772 — (2,400,124 ) — Long-term debt, net — 841,554 372,722 — 1,214,276 Operating lease liabilities — 110,998 67,608 — 178,606 Other noncurrent liabilities — 125,649 119,023 — 244,672 Total WESCO International stockholders' equity 2,202,365 3,252,590 5,202,712 (8,455,302 ) 2,202,365 Noncontrolling interests — — (6,003 ) — (6,003 ) Total liabilities and stockholders’ equity $ 3,253,717 $ 6,188,105 $ 6,402,384 $ (10,859,568 ) $ 4,984,638 Condensed Consolidating Balance Sheet December 31, 2018 (In thousands) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Cash and cash equivalents $ — $ 35,931 $ 60,412 $ — $ 96,343 Trade accounts receivable, net — — 1,166,607 — 1,166,607 Inventories — 440,422 508,304 — 948,726 Prepaid expenses and other current assets 1,123 57,586 124,523 (9,268 ) 173,964 Total current assets 1,123 533,939 1,859,846 (9,268 ) 2,385,640 Intercompany receivables, net — — 2,403,704 (2,403,704 ) — Property, buildings and equipment, net — 63,506 97,372 — 160,878 Intangible assets, net — 2,131 313,885 — 316,016 Goodwill — 257,623 1,464,980 — 1,722,603 Investments in affiliates 3,182,469 5,137,783 — (8,320,252 ) — Other assets — 2,905 16,994 — 19,899 Total assets $ 3,183,592 $ 5,997,887 $ 6,156,781 $ (10,733,224 ) $ 4,605,036 Accounts payable $ — $ 404,373 $ 389,975 $ — $ 794,348 Short-term debt — — 30,785 — 30,785 Other current liabilities — 86,600 159,481 (9,268 ) 236,813 Total current liabilities — 490,973 580,241 (9,268 ) 1,061,946 Intercompany payables, net 1,048,282 1,355,422 — (2,403,704 ) — Long-term debt, net — 842,093 325,218 — 1,167,311 Other noncurrent liabilities — 126,930 119,123 — 246,053 Total WESCO International stockholders' equity 2,135,310 3,182,469 5,137,783 (8,320,252 ) 2,135,310 Noncontrolling interests — — (5,584 ) — (5,584 ) Total liabilities and stockholders’ equity $ 3,183,592 $ 5,997,887 $ 6,156,781 $ (10,733,224 ) $ 4,605,036

OTHER FINANCIAL INFORMATION Con

OTHER FINANCIAL INFORMATION Condensed Income Statement (Tables)	3 Months Ended
	Mar. 31, 2019
Condensed Income Statements, Captions [Line Items]
Condensed Income Statement [Table Text Block]	Condensed Consolidating Statement of Income and Comprehensive Income Three Months Ended March 31, 2018 (In thousands) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 882,399 $ 1,150,110 $ (38,594 ) $ 1,993,915 Cost of goods sold (excluding depreciation and amortization) — 716,258 936,302 (38,594 ) 1,613,966 Selling, general and administrative expenses — 150,482 140,347 — 290,829 Depreciation and amortization — 4,616 11,263 — 15,879 Results of affiliates’ operations 42,971 45,200 — (88,171 ) — Net interest and other — 13,816 5,967 — 19,783 Income tax (benefit) expense — (544 ) 11,031 — 10,487 Net income 42,971 42,971 45,200 (88,171 ) 42,971 Net loss attributable to noncontrolling interests — — (1,450 ) — (1,450 ) Net income attributable to WESCO International $ 42,971 $ 42,971 $ 46,650 $ (88,171 ) $ 44,421 Other comprehensive loss: Foreign currency translation adjustments (28,800 ) (28,800 ) (28,800 ) 57,600 (28,800 ) Comprehensive income attributable to WESCO International $ 14,171 $ 14,171 $ 17,850 $ (30,571 ) $ 15,621 Condensed Consolidating Statement of Income and Comprehensive Income Three Months Ended March 31, 2019 (In thousands) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net sales $ — $ 857,982 $ 1,142,394 $ (39,109 ) $ 1,961,267 Cost of goods sold (excluding depreciation and amortization) — 689,556 928,324 (39,109 ) 1,578,771 Selling, general and administrative expenses — 152,429 144,099 — 296,528 Depreciation and amortization — 4,555 10,687 — 15,242 Results of affiliates’ operations 41,950 42,413 — (84,363 ) — Net interest and other — 12,034 5,086 — 17,120 Income tax expense — (129 ) 11,785 — 11,656 Net income 41,950 41,950 42,413 (84,363 ) 41,950 Net loss attributable to noncontrolling interests — — (419 ) — (419 ) Net income attributable to WESCO International $ 41,950 $ 41,950 $ 42,832 $ (84,363 ) $ 42,369 Other comprehensive loss: Foreign currency translation adjustments 22,517 22,517 22,517 (45,034 ) 22,517 Comprehensive income attributable to WESCO International $ 64,467 $ 64,467 $ 65,349 $ (129,397 ) $ 64,886

OTHER FINANCIAL INFORMATION C_2

OTHER FINANCIAL INFORMATION Condensed Cash Flow Statement (Tables)	3 Months Ended
	Mar. 31, 2019
Condensed Cash Flow Statements, Captions [Line Items]
Condensed Cash Flow Statement [Table Text Block]	Condensed Consolidating Statement of Cash Flows Three Months Ended March 31, 2018 (In thousands) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net cash provided by (used in) operating activities $ 5,497 $ 57,694 $ (10,198 ) $ — $ 52,993 Investing activities: Capital expenditures — (2,954 ) (4,708 ) — (7,662 ) Dividends received from subsidiaries — 22,744 — (22,744 ) — Other — (18,908 ) (8,760 ) 18,908 (8,760 ) Net cash provided by (used in) investing activities — 882 (13,468 ) (3,836 ) (16,422 ) Financing activities: Borrowings — 58,000 515,663 (22,744 ) 550,919 Repayments (3,836 ) (90,000 ) (477,220 ) 3,836 (567,220 ) Repurchases of common stock (1,661 ) — — — (1,661 ) Dividends paid by subsidiaries — — (22,744 ) 22,744 — Decrease in bank overdrafts — (10,575 ) — — (10,575 ) Other — (290 ) — — (290 ) Net cash (used in) provided by financing activities (5,497 ) (42,865 ) 15,699 3,836 (28,827 ) Effect of exchange rate changes on cash and cash equivalents — — (1,800 ) — (1,800 ) Net change in cash and cash equivalents — 15,711 (9,767 ) — 5,944 Cash and cash equivalents at the beginning of period — 50,602 67,351 — 117,953 Cash and cash equivalents at the end of period $ — $ 66,313 $ 57,584 $ — $ 123,897 Condensed Consolidating Statement of Cash Flows Three Months Ended March 31, 2019 (In thousands) WESCO International, Inc. WESCO Distribution, Inc. Non-Guarantor Subsidiaries Consolidating and Eliminating Entries Consolidated Net cash (used in) provided by operating activities $ 5,157 $ 27,122 $ (3,410 ) $ — $ 28,869 Investing activities: Acquisition payments — (27,742 ) — — (27,742 ) Capital expenditures — (2,513 ) (8,315 ) — (10,828 ) Dividends received from subsidiaries — 22,095 — (22,095 ) — Other — (19,510 ) 53 19,510 53 Net cash used in investing activities — (27,670 ) (8,262 ) (2,585 ) (38,517 ) Financing activities: Borrowings — 139,134 330,196 (22,095 ) 447,235 Repayments (2,585 ) (140,134 ) (289,674 ) 2,585 (429,808 ) Repurchases of common stock (2,572 ) — — — (2,572 ) Dividends paid by subsidiaries — — (22,095 ) 22,095 — Increase in bank overdrafts — 4,639 — — 4,639 Other — (248 ) — — (248 ) Net cash provided by (used in) financing activities (5,157 ) 3,391 18,427 2,585 19,246 Effect of exchange rate changes on cash and cash equivalents — — 159 — 159 Net change in cash and cash equivalents — 2,843 6,914 — 9,757 Cash and cash equivalents at the beginning of period — 35,931 60,412 — 96,343 Cash and cash equivalents at the end of period $ — $ 38,774 $ 67,326 $ — $ 106,100

GOODWILL (Tables)

GOODWILL (Tables)	3 Months Ended
	Mar. 31, 2019
Goodwill [Line Items]
Schedule of Goodwill [Table Text Block]	Three Months Ended March 31 (In thousands) 2019 Beginning balance January 1 $ 1,722,603 Foreign currency exchange rate changes 12,642 Additions to goodwill for acquisitions 5,526 Ending balance March 31 $ 1,740,771

REVENUE (Tables)

REVENUE (Tables)	3 Months Ended
	Mar. 31, 2019
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue [Table Text Block]	The following tables disaggregate WESCO’s revenue by end market and geography: Three Months Ended March 31 (In thousands) 2019 2018 Industrial $ 736,906 $ 758,976 Construction 633,288 637,800 Utility 308,269 315,546 Commercial, Institutional and Government 282,804 281,593 Total by end market $ 1,961,267 $ 1,993,915 Three Months Ended March 31 (In thousands) 2019 2018 United States $ 1,460,991 $ 1,482,718 Canada (1) 384,596 398,738 Other International (1) 115,680 112,459 Total by geography $ 1,961,267 $ 1,993,915 (1) The prior period has been reclassified to conform to the current period presentation.
Revenue Recognition, Revenue Reductions [Policy Text Block]	WESCO’s revenues are adjusted for variable consideration, which includes customer volume rebates, returns, and discounts. WESCO measures variable consideration by estimating expected outcomes using analysis and inputs based upon anticipated performance, historical data, as well as current and forecasted information. Measurement and recognition of variable consideration is reviewed by management on a monthly basis and revenue is adjusted accordingly. Variable consideration reduced revenue for the three months ended March 31, 2019 and 2018 by approximately $25.5 million and $23.8 million , respectively.

LEASES (Tables)

LEASES (Tables)	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Lease, Cost [Table Text Block]	Three Months Ended March 31 (In thousands) 2019 Operating lease cost $ 18,003 Short-term lease cost 11 Variable lease cost 5,321 Total lease cost $ 23,335
Lessee, Operating Lease, Liability, Maturity [Table Text Block]	(In thousands) 2019 $ 59,033 2020 61,233 2021 49,587 2022 36,767 2023 27,547 Thereafter 45,701 Total undiscounted operating lease payments 279,868 Less: interest (42,026 ) Total operating lease liabilities $ 237,842
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]	Years ending December 31 (In thousands) 2019 $ 71,640 2020 59,594 2021 47,264 2022 34,490 2023 24,493 Thereafter 40,302

ORGANIZATION (Details)

ORGANIZATION (Details)	Mar. 31, 2019customerscountriesbranches
Restructuring Cost and Reserve [Line Items]
Active customers (in customers) | customers	70,000
Full service branches (in branches) | branches	500
Additional countries (in countries) | countries	15

ORGANIZATION Organization (Deta

ORGANIZATION Organization (Details)	3 Months Ended
	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Distribution Centers	10

ACCOUNTING POLICIES (Details)

ACCOUNTING POLICIES (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Prepaid expenses and other current assets	$ 62,406	$ 76,980
Assets, Current	2,513,750	2,385,640
Goodwill	1,740,771	1,722,603
Liabilities and Equity	4,984,638	4,605,036
Other Accrued Liabilities, Current	169,619	105,461
Liabilities, Current	1,150,722	1,061,946
Assets	4,984,638	4,605,036
Deferred Tax Liabilities, Net, Noncurrent	145,501	143,967
Liabilities	2,788,276	2,475,310
Retained earnings	2,349,300	2,307,462	$ 2,124,535	$ 2,079,697
Accumulated other comprehensive income	(385,918)	(408,435)	$ (341,390)	$ (312,590)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 2,196,362	$ 2,129,726

ACQUISITIONS - ACQUISITIONS (De

ACQUISITIONS - ACQUISITIONS (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)branches	Mar. 31, 2018USD ($)
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	$ 34,812
Business Acquisition, Effective Date of Acquisition	Mar. 5, 2019
Business Acquisition, Revenue Reported by Acquired Entity for Last Annual Period	$ 100,000
Goodwill, Acquired During Period	$ 5,526
Number of Stores | branches	500
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	$ 7,070
Payments to Acquire Businesses, Gross	$ 27,742	$ 0

SCHEDULE OF SHARE-BASED COMPENS

SCHEDULE OF SHARE-BASED COMPENSATION, STOCK OPTIONS AND STOCK APPRECIATION RIGHTS AWARD ACTIVITY (Details) - Stock Appreciation Rights (SARs) [Member] - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
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	$ 54.63
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	$ 9,217
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$ 59.25		$ 59.26
Share-based Compensation Arrangement By Share-based Payment Award, Options and Stock Appreciation Rights, Outstanding [Roll Forward]
Beginning of Year (in shares)	1,815,662
Grants in Period (in shares)	213,618	491,229
Exercises in Period (in shares)	51,635
Forfeitures in Period (in shares)	26,236
Weighted Average Exercise Price, Exercises in Period (in dollars per share)	$ 35.11
Weighted Average Exercise Price, Forfeitures in Period (in dollars per share)	70
Weighted Average Exercise Price, Exercisable (in dollars per share)	$ 58.38
Weighted Average Remaining Contractual Term, Outstanding (in years)	6 years 3 months
Weighted Average Remaining Contractual Term, Exercisable (in years)	5 years 3 months
Aggregate Intrinsic Value, Outstanding	$ 9,222
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number	2,487,380		2,351,633

SCHEDULE OF SHARE-BASED PAYMENT

SCHEDULE OF SHARE-BASED PAYMENT AWARD, VALUATION ASSUMPTIONS (Details) - $ / shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate	2.50%	2.50%
Expected life (in years)	5 years	5 years
WESCO expected volatility	29.00%	28.00%
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	213,618	491,229
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 16.36	$ 18.40
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	175,544	114,269
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 54.64	$ 62.81
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	126,874	44,144
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 54.64	$ 62.80

SUMMARY OF RESTRICTED STOCK UNI

SUMMARY OF RESTRICTED STOCK UNITS (Details) - Restricted Stock Units (RSUs) [Member] - $ / shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Unvested (in shares)	389,277		327,798
Granted (in shares)	175,544	114,269
Vested (in shares)	(112,500)
Forfeited (in shares)	(1,565)
Unvested, Weighted Average Fair Value (in dollars per share)	$ 60.48		$ 57.87
Granted, Weighted Average Fair Value (in dollars per share)	54.64	$ 62.81
Vested in Period, Weighted Average Fair Value (in dollars per share)	43.58
Forfeited in Period, Weighted Average Fair Value (in dollars per share)	$ 57.49

SUMMARY OF PERFORMANCE-BASED AW

SUMMARY OF PERFORMANCE-BASED AWARDS (Details) - $ / shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Unvested (in shares)	204,588		138,896
Granted (in shares)	126,874	44,144
Vested (in shares)	(25,696)
Forfeited (in shares)	(35,486)
Unvested, Weighted Average Fair Value (in dollars per share)	$ 60.11		$ 59.33
Granted, Weighted Average Fair Value (in dollars per share)	54.64	$ 62.80
Vested in Period, Weighted Average Fair Value (in dollars per share)	42.44
Forfeited in Period, Weighted Average Fair Value (in dollars per share)	$ 50.79
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)	187,081
Share-based Compensation Award, Tranche Two [Member] | Net Income Growth Rate [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Unvested (in shares)	80,944
Share-based Compensation Award, Tranche Two [Member] | Earnings Per Share Growth [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Unvested (in shares)	84,787
Share-based Compensation Award, Tranche Two [Member] | Return on Net Assets [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Unvested (in shares)	21,350

SCHEDULE OF SHARE-BASED PAYME_2

SCHEDULE OF SHARE-BASED PAYMENT AWARD, PERFORMANCE-BASED AWARDS, VALUATION ASSUMPTIONS (Details)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
WESCO expected volatility	29.00%	28.00%
Risk free interest rate	2.50%	2.50%

STOCK-BASED COMPENSATION (Detai

STOCK-BASED COMPENSATION (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 4.7	$ 3.9
Total unrecognized compensation cost	$ 36.6
Share-based Compensation Award, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance-based awards outstanding (in shares)	17,507
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)	187,081
Scenario, Forecast [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ 15.4	$ 0.7	$ 7	$ 13.5

SCHEDULE OF EARNINGS PER SHARE,

SCHEDULE OF EARNINGS PER SHARE, BASIC AND DILUTED (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share [Abstract]
Net income (loss) attributable to WESCO International, Inc.	$ 42,369	$ 44,421
Weighted average common shares outstanding used in computing basic earnings per share (in shares)	45,076	47,038
Common shares issuable upon exercise of dilutive stock options (in shares)	415	570
Weighted average common shares outstanding and common share equivalents used in computing diluted earnings per share (in shares)	45,491	47,608
Earnings Per Share, Basic and Diluted [Abstract]
Basic (in dollars per share)	$ 0.94	$ 0.94
Diluted (in dollars per share)	$ 0.93	$ 0.93

EARNINGS PER SHARE (Details)

EARNINGS PER SHARE (Details) - shares shares in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Equity Award [Domain]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1.8	1.5

EARNINGS PER SHARE Accelerated

EARNINGS PER SHARE Accelerated Share Repurchase (Details) - USD ($) $ in Thousands	3 Months Ended		4 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 07, 2019	Dec. 31, 2018	Dec. 31, 2017
Accelerated Share Repurchases [Line Items]
Payments for Repurchase of Common Stock	$ (2,572)	$ (1,661)
Stock Repurchase Program, Authorized Amount				$ 400,000	$ 300,000
Treasury Stock, Shares, Acquired	365,272		1,953,167
Stock Repurchase Program Expiration Date	Dec. 31, 2020
Treasury Stock, Common [Member]
Accelerated Share Repurchases [Line Items]
Payments for Repurchase of Common Stock	$ (100,000)

EMPLOYEE BENEFIT PLANS (Details

EMPLOYEE BENEFIT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Retirement Benefits [Abstract]
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 100
Schedule of Employee Benefit Plans [Line Items]
Defined Benefit Plan, Service Cost	1,149	$ 1,347
Postemployment Benefits, Period Expense	12,600	$ 10,700
Deferred Compensation Liability, Classified, Noncurrent	$ 23,100		$ 21,900
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
	Mar. 31, 2019	Mar. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 100
Service cost	1,149	$ 1,347
Interest cost	1,089	1,066
Expected return on plan assets	(1,422)	(1,540)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(16)	(12)
Net periodic benefit cost	800	861
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Other Nonoperating Gains (Losses)	$ (300)	$ (500)

INCOME TAXES (Details)

INCOME TAXES (Details)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Tax Contingency [Line Items]
Effective tax rate	21.70%	19.61727%

INCOME TAXES Income Tax Rates (

INCOME TAXES Income Tax Rates (Details)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation, Percent	21.70%	19.61727%

OTHER FINANCIAL INFORMATION (De

OTHER FINANCIAL INFORMATION (Details) - Unsecured Debt [Member] $ in Millions	Mar. 31, 2019USD ($)
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	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Condensed Financial Information [Line Items]
Cash and cash equivalents	$ 106,100	$ 96,343	$ 123,897	$ 117,953
Trade accounts receivable, net	1,268,565	1,166,607
Inventories, net	1,001,353	948,726
Prepaid Expense and Other Assets, Current	62,406	76,980
Total current assets	2,513,750	2,385,640
Property, buildings and equipment, net	166,688	160,878
Operating Lease, Right-of-Use Asset	232,989	0
Intangible assets, net	310,453	316,016
Goodwill and other intangibles, net	1,740,771	1,722,603
Other assets	19,987	19,899
Total assets	4,984,638	4,605,036
Accounts payable	870,242	794,348
Short-term debt	27,313	30,785
Total current liabilities	1,150,722	1,061,946
Long-term Debt, Excluding Current Maturities	1,214,276	1,167,311
Operating Lease, Liability, Noncurrent	178,606	0
Total stockholders' equity	2,202,365	2,135,310
Stockholders' Equity Attributable to Noncontrolling Interest	6,003	5,584	5,046	3,596
Total liabilities and stockholders' equity	4,984,638	4,605,036
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	1,127	1,123
Total current assets	1,127	1,123
Intercompany receivables, net	0	0
Property, buildings and equipment, net	0	0
Operating Lease, Right-of-Use Asset	0
Intangible assets, net	0	0
Goodwill and other intangibles, net	0	0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	3,252,590	3,182,469
Other assets	0	0
Total assets	3,253,717	3,183,592
Accounts payable	0	0
Short-term debt	0	0
Other Liabilities, Current	0	0
Total current liabilities	0	0
Intercompany payables, net	1,051,352	1,048,282
Long-term Debt, Excluding Current Maturities	0	0
Operating Lease, Liability, Noncurrent	0
Liabilities, Other than Long-term Debt, Noncurrent	0	0
Total stockholders' equity	2,202,365	2,135,310
Stockholders' Equity Attributable to Noncontrolling Interest	0	0
Total liabilities and stockholders' equity	3,253,717	3,183,592
Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Cash and cash equivalents	38,774	35,931	66,313	50,602
Trade accounts receivable, net	0	0
Inventories, net	453,738	440,422
Prepaid Expense and Other Assets, Current	22,341	57,586
Total current assets	514,853	533,939
Intercompany receivables, net	0	0
Property, buildings and equipment, net	68,829	63,506
Operating Lease, Right-of-Use Asset	139,397
Intangible assets, net	1,974	2,131
Goodwill and other intangibles, net	257,623	257,623
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	5,202,712	5,137,783
Other assets	2,717	2,905
Total assets	6,188,105	5,997,887
Accounts payable	426,015	404,373
Short-term debt	0	0
Other Liabilities, Current	82,527	86,600
Total current liabilities	508,542	490,973
Intercompany payables, net	1,348,772	1,355,422
Long-term Debt, Excluding Current Maturities	841,554	842,093
Operating Lease, Liability, Noncurrent	110,998
Liabilities, Other than Long-term Debt, Noncurrent	125,649	126,930
Total stockholders' equity	3,252,590	3,182,469
Stockholders' Equity Attributable to Noncontrolling Interest	0	0
Total liabilities and stockholders' equity	6,188,105	5,997,887
Non-Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Cash and cash equivalents	67,326	60,412	57,584	67,351
Trade accounts receivable, net	1,268,565	1,166,607
Inventories, net	547,615	508,304
Prepaid Expense and Other Assets, Current	118,406	124,523
Total current assets	2,001,912	1,859,846
Intercompany receivables, net	2,400,124	2,403,704
Property, buildings and equipment, net	97,859	97,372
Operating Lease, Right-of-Use Asset	93,592
Intangible assets, net	308,479	313,885
Goodwill and other intangibles, net	1,483,148	1,464,980
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0	0
Other assets	17,270	16,994
Total assets	6,402,384	6,156,781
Accounts payable	444,227	389,975
Short-term debt	27,313	30,785
Other Liabilities, Current	174,782	159,481
Total current liabilities	646,322	580,241
Intercompany payables, net	0	0
Long-term Debt, Excluding Current Maturities	372,722	325,218
Operating Lease, Liability, Noncurrent	67,608
Liabilities, Other than Long-term Debt, Noncurrent	119,023	119,123
Total stockholders' equity	5,202,712	5,137,783
Stockholders' Equity Attributable to Noncontrolling Interest	6,003	5,584
Total liabilities and stockholders' equity	6,402,384	6,156,781
Consolidated Entities [Member]
Condensed Financial Information [Line Items]
Cash and cash equivalents	106,100	96,343	123,897	117,953
Trade accounts receivable, net	1,268,565	1,166,607
Inventories, net	1,001,353	948,726
Prepaid Expense and Other Assets, Current	137,732	173,964
Total current assets	2,513,750	2,385,640
Intercompany receivables, net	0	0
Property, buildings and equipment, net	166,688	160,878
Operating Lease, Right-of-Use Asset	232,989
Intangible assets, net	310,453	316,016
Goodwill and other intangibles, net	1,740,771	1,722,603
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0	0
Other assets	19,987	19,899
Total assets	4,984,638	4,605,036
Accounts payable	870,242	794,348
Short-term debt	27,313	30,785
Other Liabilities, Current	253,167	236,813
Total current liabilities	1,150,722	1,061,946
Intercompany payables, net	0	0
Long-term Debt, Excluding Current Maturities	1,214,276	1,167,311
Operating Lease, Liability, Noncurrent	178,606
Liabilities, Other than Long-term Debt, Noncurrent	244,672	246,053
Total stockholders' equity	2,202,365	2,135,310
Stockholders' Equity Attributable to Noncontrolling Interest	6,003	5,584
Total liabilities and stockholders' equity	4,984,638	4,605,036
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	(4,142)	(9,268)
Total current assets	(4,142)	(9,268)
Intercompany receivables, net	(2,400,124)	(2,403,704)
Property, buildings and equipment, net	0	0
Operating Lease, Right-of-Use Asset	0
Intangible assets, net	0	0
Goodwill and other intangibles, net	0	0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	(8,455,302)	(8,320,252)
Other assets	0	0
Total assets	(10,859,568)	(10,733,224)
Accounts payable	0	0
Short-term debt	0	0
Other Liabilities, Current	(4,142)	(9,268)
Total current liabilities	(4,142)	(9,268)
Intercompany payables, net	(2,400,124)	(2,403,704)
Long-term Debt, Excluding Current Maturities	0	0
Operating Lease, Liability, Noncurrent	0
Liabilities, Other than Long-term Debt, Noncurrent	0	0
Total stockholders' equity	(8,455,302)	(8,320,252)
Stockholders' Equity Attributable to Noncontrolling Interest	0	0
Total liabilities and stockholders' equity	$ (10,859,568)	$ (10,733,224)

CONDENSED CONSOLIDATED INCOME S

CONDENSED CONSOLIDATED INCOME STATEMENTS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Condensed Financial Information [Line Items]
Revenues	$ 1,961,267	$ 1,993,915
Cost of goods sold	1,578,771	1,613,966
Selling, general and administrative expense	296,528	290,829
Depreciation and amortization	15,242	15,879
Provision for income taxes	11,656	10,487
Net income (loss)	41,950	42,971
Less: Net (loss) income attributable to noncontrolling interest	(419)	(1,450)
Net income (loss) attributable to WESCO International, Inc.	42,369	44,421
Comprehensive Income:
Foreign currency translation adjustment	22,517	(28,800)
Comprehensive income attributable to WESCO International, Inc.	64,886	15,621
Parent Company [Member]
Condensed Financial Information [Line Items]
Revenues	0	0
Cost of goods sold	0	0
Selling, general and administrative expense	0	0
Depreciation and amortization	0	0
Income (Loss) from Subsidiaries, before Tax	41,950	42,971
Other Nonoperating Income (Expense)	0	0
Provision for income taxes	0	0
Net income (loss)	41,950	42,971
Less: Net (loss) income attributable to noncontrolling interest	0	0
Net income (loss) attributable to WESCO International, Inc.	41,950	42,971
Comprehensive Income:
Foreign currency translation adjustment	22,517	(28,800)
Comprehensive income attributable to WESCO International, Inc.	64,467	14,171
Non-Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Revenues	1,142,394	1,150,110
Cost of goods sold	928,324	936,302
Selling, general and administrative expense	144,099	140,347
Depreciation and amortization	10,687	11,263
Income (Loss) from Subsidiaries, before Tax	0	0
Other Nonoperating Income (Expense)	5,086	5,967
Provision for income taxes	11,785	11,031
Net income (loss)	42,413	45,200
Less: Net (loss) income attributable to noncontrolling interest	(419)	(1,450)
Net income (loss) attributable to WESCO International, Inc.	42,832	46,650
Comprehensive Income:
Foreign currency translation adjustment	22,517	(28,800)
Comprehensive income attributable to WESCO International, Inc.	65,349	17,850
Consolidated Entities [Member]
Condensed Financial Information [Line Items]
Revenues	1,961,267	1,993,915
Cost of goods sold	1,578,771	1,613,966
Selling, general and administrative expense	296,528	290,829
Depreciation and amortization	15,242	15,879
Income (Loss) from Subsidiaries, before Tax	0	0
Other Nonoperating Income (Expense)	(17,120)	(19,783)
Provision for income taxes	11,656	10,487
Net income (loss)	41,950	42,971
Less: Net (loss) income attributable to noncontrolling interest	(419)	(1,450)
Net income (loss) attributable to WESCO International, Inc.	42,369	44,421
Comprehensive Income:
Foreign currency translation adjustment	22,517	(28,800)
Comprehensive income attributable to WESCO International, Inc.	64,886	15,621
Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Revenues	857,982	882,399
Cost of goods sold	689,556	716,258
Selling, general and administrative expense	152,429	150,482
Depreciation and amortization	4,555	4,616
Income (Loss) from Subsidiaries, before Tax	42,413	45,200
Other Nonoperating Income (Expense)	(12,034)	(13,816)
Provision for income taxes	(129)	(544)
Net income (loss)	41,950	42,971
Less: Net (loss) income attributable to noncontrolling interest	0	0
Net income (loss) attributable to WESCO International, Inc.	41,950	42,971
Comprehensive Income:
Foreign currency translation adjustment	22,517	(28,800)
Comprehensive income attributable to WESCO International, Inc.	64,467	14,171
Consolidation, Eliminations [Member]
Condensed Financial Information [Line Items]
Revenues	(39,109)	(38,594)
Cost of goods sold	(39,109)	(38,594)
Selling, general and administrative expense	0	0
Depreciation and amortization	0	0
Income (Loss) from Subsidiaries, before Tax	(84,363)	(88,171)
Other Nonoperating Income (Expense)	0	0
Provision for income taxes	0	0
Net income (loss)	(84,363)	(88,171)
Less: Net (loss) income attributable to noncontrolling interest	0	0
Net income (loss) attributable to WESCO International, Inc.	(84,363)	(88,171)
Comprehensive Income:
Foreign currency translation adjustment	(45,034)	57,600
Comprehensive income attributable to WESCO International, Inc.	(129,397)	(30,571)
Pension Plan [Member]
Condensed Financial Information [Line Items]
Other Nonoperating Gains (Losses)	$ (300)	$ (500)

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENT OF CASH FLOWS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	$ 53	$ (8,760)
Net cash (used) provided by operating activities	28,869	52,993
Payments to Acquire Businesses, Gross	27,742	0
Investing Activities:
Capital expenditures	(10,828)	(7,662)
Net cash used in investing activities	(38,517)	(16,422)
Financing Activities:
Proceeds from (Repayments of) Bank Overdrafts	4,639	(10,575)
Payments for Repurchase of Common Stock	(2,572)	(1,661)
Proceeds from (Payments for) Other Financing Activities	(248)	(290)
Net cash used in financing activities	19,246	(28,827)
Effect of exchange rate changes on cash and cash equivalents	159	(1,800)
Net change in cash and cash equivalents	9,757	5,944
Cash and cash equivalents at the beginning of period	96,343	117,953
Cash and cash equivalents at the end of period	106,100	123,897
Parent Company [Member]
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	0	0
Net cash (used) provided by operating activities	5,157	5,497
Payments to Acquire Businesses, Gross	0
Investing Activities:
Capital expenditures	0	0
Proceeds from Dividends Received	0	0
Net cash used in investing activities	0	0
Financing Activities:
Borrowings	0	0
Repayments	(2,585)	(3,836)
Proceeds from (Repayments of) Bank Overdrafts	0	0
SEC Schedule, 12-04, Cash Dividends Paid to Registrant, Subsidiaries and Equity Method Investees	0	0
Payments for Repurchase of Common Stock	(2,572)	1,661
Proceeds from (Payments for) Other Financing Activities	0	0
Net cash used in financing activities	(5,157)	(5,497)
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	(19,510)	(18,908)
Net cash (used) provided by operating activities	27,122	57,694
Payments to Acquire Businesses, Gross	(27,742)
Investing Activities:
Capital expenditures	(2,513)	(2,954)
Proceeds from Dividends Received	22,095	22,744
Net cash used in investing activities	(27,670)	882
Financing Activities:
Borrowings	139,134	58,000
Repayments	(140,134)	(90,000)
Proceeds from (Repayments of) Bank Overdrafts	4,639	(10,575)
SEC Schedule, 12-04, Cash Dividends Paid to Registrant, Subsidiaries and Equity Method Investees	0	0
Payments for Repurchase of Common Stock		0
Payments for Repurchase of Private Placement	0
Proceeds from (Payments for) Other Financing Activities	(248)	(290)
Net cash used in financing activities	3,391	(42,865)
Effect of exchange rate changes on cash and cash equivalents	0	0
Net change in cash and cash equivalents	2,843	15,711
Cash and cash equivalents at the beginning of period	35,931	50,602
Cash and cash equivalents at the end of period	38,774	66,313
Non-Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	53	(8,760)
Net cash (used) provided by operating activities	(3,410)	(10,198)
Payments to Acquire Businesses, Gross	0
Investing Activities:
Capital expenditures	(8,315)	(4,708)
Proceeds from Dividends Received	0	0
Net cash used in investing activities	(8,262)	(13,468)
Financing Activities:
Borrowings	330,196	515,663
Repayments	(289,674)	(477,220)
Proceeds from (Repayments of) Bank Overdrafts	0	0
SEC Schedule, 12-04, Cash Dividends Paid to Registrant, Subsidiaries and Equity Method Investees	(22,095)	(22,744)
Payments for Repurchase of Common Stock	0	0
Proceeds from (Payments for) Other Financing Activities	0	0
Net cash used in financing activities	18,427	15,699
Effect of exchange rate changes on cash and cash equivalents	159	(1,800)
Net change in cash and cash equivalents	6,914	(9,767)
Cash and cash equivalents at the beginning of period	60,412	67,351
Cash and cash equivalents at the end of period	67,326	57,584
Consolidated Entities [Member]
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	53	(8,760)
Net cash (used) provided by operating activities	28,869	52,993
Payments to Acquire Businesses, Gross	(27,742)
Investing Activities:
Capital expenditures	(10,828)	(7,662)
Proceeds from Dividends Received	0	0
Net cash used in investing activities	(38,517)	(16,422)
Financing Activities:
Borrowings	447,235	550,919
Repayments	(429,808)	(567,220)
Proceeds from (Repayments of) Bank Overdrafts	4,639	(10,575)
SEC Schedule, 12-04, Cash Dividends Paid to Registrant, Subsidiaries and Equity Method Investees	0	0
Payments for Repurchase of Common Stock	2,572	1,661
Proceeds from (Payments for) Other Financing Activities	(248)	(290)
Net cash used in financing activities	19,246	(28,827)
Effect of exchange rate changes on cash and cash equivalents	159	(1,800)
Net change in cash and cash equivalents	9,757	5,944
Cash and cash equivalents at the beginning of period	96,343	117,953
Cash and cash equivalents at the end of period	106,100	123,897
Consolidation, Eliminations [Member]
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	19,510	18,908
Net cash (used) provided by operating activities	0	0
Payments to Acquire Businesses, Gross	0
Investing Activities:
Capital expenditures	0	0
Proceeds from Dividends Received	(22,095)	(22,744)
Net cash used in investing activities	(2,585)	(3,836)
Financing Activities:
Borrowings	(22,095)	(22,744)
Repayments	(2,585)	(3,836)
Proceeds from (Repayments of) Bank Overdrafts	0	0
SEC Schedule, 12-04, Cash Dividends Paid to Registrant, Subsidiaries and Equity Method Investees	(22,095)	(22,744)
Payments for Repurchase of Common Stock	0	0
Proceeds from (Payments for) Other Financing Activities	0	0
Net cash used in financing activities	2,585	3,836
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

Subsequent Events (Details)

Subsequent Events (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)
Subsequent Event [Line Items]
Business Acquisition, Effective Date of Acquisition	Mar. 5, 2019
Business Acquisition, Revenue Reported by Acquired Entity for Last Annual Period	$ 100

GOODWILL (Details)

GOODWILL (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Goodwill [Line Items]
Goodwill	$ 1,740,771	$ 1,722,603
Goodwill, Foreign Currency Translation Gain (Loss)	12,642
Goodwill, Acquired During Period	$ 5,526

REVENUE (Details)

REVENUE (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Deferred Revenue	$ 8,800		$ 11,800
Revenue from Contract with Customer, Excluding Assessed Tax	1,961,267	$ 1,993,915
Cost of goods sold	1,578,771	1,613,966
Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	736,906	758,976
Construction [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	633,288	637,800
Utility [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	308,269	315,546
Commercial, Institutional and Government [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	282,804	281,593
UNITED STATES
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,460,991	1,482,718
CANADA
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	384,596	398,738
Non-US [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	115,680	112,459
Shipping and Handling [Member]
Disaggregation of Revenue [Line Items]
Cost of goods sold	$ 17,000	$ 18,200

REVENUE Deferred Revenue (Detai

REVENUE Deferred Revenue (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Deferred Revenue	$ 8.8	$ 11.8

REVENUE Shipping and Handling C

REVENUE Shipping and Handling Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cost of goods sold	$ 1,578,771	$ 1,613,966
Shipping and Handling [Member]
Cost of goods sold	$ 17,000	$ 18,200

REVENUE Variable Consideration

REVENUE Variable Consideration (Details)	3 Months Ended
	Mar. 31, 2019
Revenue from Contract with Customer [Abstract]
Revenue Recognition, Revenue Reductions [Policy Text Block]	WESCO’s revenues are adjusted for variable consideration, which includes customer volume rebates, returns, and discounts. WESCO measures variable consideration by estimating expected outcomes using analysis and inputs based upon anticipated performance, historical data, as well as current and forecasted information. Measurement and recognition of variable consideration is reviewed by management on a monthly basis and revenue is adjusted accordingly. Variable consideration reduced revenue for the three months ended March 31, 2019 and 2018 by approximately $25.5 million and $23.8 million , respectively.

LEASES (Details)

LEASES (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months	$ 59,033
Operating Leases, Future Minimum Payments Due, Next Twelve Months		$ 71,640
Operating Lease, Weighted Average Remaining Lease Term	5 years 6 months
Operating Lease, Right-of-Use Asset	$ 232,989	0
Operating Lease, Cost	18,003
Operating Lease, Payments	18,012
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	8,092
Short-term Lease, Cost	11
Variable Lease, Cost	5,321
Lease, Cost	23,335
Operating Lease, Liability, Current	59,236
Operating Lease, Liability, Noncurrent	178,606	0
Operating Lease, Liability	$ 237,842
Operating Lease, Weighted Average Discount Rate, Percent	4.60%
Operating Leases, Future Minimum Payments, Due in Two Years		59,594
Operating Leases, Future Minimum Payments, Due in Three Years		47,264
Operating Leases, Future Minimum Payments, Due in Four Years		34,490
Operating Leases, Future Minimum Payments, Due in Five Years		24,493
Operating Leases, Future Minimum Payments, Due Thereafter		$ 40,302
Lessee, Operating Lease, Liability, Payments, Due Year Two	$ 61,233
Lessee, Operating Lease, Liability, Payments, Due Year Three	49,587
Lessee, Operating Lease, Liability, Payments, Due Year Four	36,767
Lessee, Operating Lease, Liability, Payments, Due Year Five	27,547
Lessee, Operating Lease, Liability, Payments, Due after Year Five	45,701
Lessee, Operating Lease, Liability, Payments, Due	279,868
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	$ (42,026)