0000929008-19-000033 | 10-Q | XBRL Viewer

COVER PAGE Document - shares	9 Months Ended
COVER PAGE Document - shares	Sep. 30, 2019	Oct. 31, 2019
Cover page.
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2019
Document Transition Report	false
Entity File Number	001-14989
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	25-1723342
Entity Address, Address Line One	225 West Station Square DriveSuite 700
Entity Address, City or Town	Pittsburgh,
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	15219
City Area Code	412
Local Phone Number	454-2200
Title of 12(b) Security	Common Stock, par value $.01 per share
Trading Symbol	WCC
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		41,796,445
Entity Registrant Name	WESCO INTERNATIONAL INC.
Entity Central Index Key	0000929008
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS $ in Thousands	3 Months Ended	9 Months Ended
CONSOLIDATED BALANCE SHEETS $ in Thousands	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)
Depreciation, Depletion and Amortization, Nonproduction	$ 15,612	$ 46,035
Other Accrued Liabilities, Current	160,062	160,062	$ 105,461
Current Assets:
Cash and cash equivalents	138,160	138,160	96,343
Allowance for Doubtful Accounts Receivable, Current	27,122	27,122	24,468
Trade accounts receivable, net of allowance for doubtful accounts of $23,069 and $19,309 in 2014 and 2013, respectively	1,315,026	1,315,026	1,166,607
Accounts and Other Receivables, Net, Current	82,357	82,357	96,984
Inventories, net	961,997	961,997	948,726
Prepaid expenses and other current assets	80,940	80,940	76,980
Total current assets	2,578,480	2,578,480	2,385,640
Property, buildings and equipment, net of accumulated depreciation of $229,041 and $213,758 in 2014 and 2013, respectively	174,459	174,459	160,878
Operating Lease, Right-of-Use Asset	237,252	237,252	0
Intangible assets, net	293,493	293,493	316,016
Goodwill	1,746,071	1,746,071	1,722,603
Other assets	17,656	17,656	19,899
Total assets	5,047,411	5,047,411	4,605,036
Current Liabilities:
Accounts payable	849,584	849,584	794,348
Accrued payroll and benefit costs	50,205	50,205	88,105
Short-term debt	25,561	25,561	30,785
Current portion of long-term debt	338	338	25,429
Total current liabilities	1,104,524	1,104,524	1,061,946
Long-term Debt, Excluding Current Maturities	1,346,333	1,346,333	1,167,311
Operating Lease, Liability, Noncurrent	182,044	182,044	0
Other noncurrent liabilities	79,968	79,968	102,086
Deferred Tax Liabilities, Net, Noncurrent	147,832	147,832	143,967
Total liabilities	2,860,701	2,860,701	2,475,310
Commitments and Contingencies
Bank Overdrafts	18,774	18,774	17,818
Stockholders' Equity:
Preferred stock, $.01 par value; 20,000,000 shares authorized, no shares issued or outstanding	0	0	0
Additional capital	1,034,888	1,034,888	993,666
Retained earnings	2,477,259	2,477,259	2,307,462
Treasury stock, at cost; 18,247,467 and 18,179,275 shares in 2014 and 2013, respectively	(937,135)	(937,135)	(758,018)
Accumulated other comprehensive income	(382,530)	(382,530)	(408,435)
Total WESCO International stockholders' equity	2,186,710	2,186,710	2,129,726
Noncontrolling interest	(6,408)	(6,408)	(5,584)
Total stockholders' equity	2,193,118	2,193,118	2,135,310
Total liabilities and stockholders' equity	5,047,411	5,047,411	4,605,036
Common Stock [Member]
Stockholders' Equity:
Common stock	593	593	592
Common Class B [Member]
Stockholders' Equity:
Common stock	$ 43	$ 43	$ 43

CONSOLIDATED BALANCE SHEETS (Parentheticals) - USD ($)	Sep. 30, 2019	Dec. 31, 2018
Allowance for doubtful accounts	$ 27,122,000	$ 24,468,000
Accumulated depreciation	289,882,000	291,811,000
Finite-Lived Intangible Assets, Accumulated Amortization	278,856	249,539
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ 9,371,000	$ 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)	21,849,933	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)	59,294,497	59,157,696
Common stock, shares outstanding (in shares)	41,783,995	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 INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues	$ 2,148,110	$ 2,067,245	$ 6,259,465	$ 6,165,154
Cost of goods sold	1,747,913	1,670,037	5,067,799	4,988,103
Selling, general and administrative expense	290,852	284,073	883,222	867,790
Depreciation and amortization	15,612	15,618	46,035	47,321
Income from operations	93,733	97,517	262,409	261,940
Nonoperating Income (Expense)	13,508	17,050	47,934	54,574
Income before income taxes	80,225	80,467	214,475	207,366
Provision for income taxes	15,886	13,822	44,970	40,077
Net income	64,339	66,645	169,505	167,289
Net (loss) income attributable to noncontrolling interest	(156)	(204)	(824)	(1,921)
Net income attributable to WESCO International, Inc.	64,495	66,849	170,329	169,210
Comprehensive Income:
Foreign currency translation adjustment	(16,856)	20,486	25,905	(37,029)
Comprehensive income attributable to WESCO International, Inc.	$ 47,639	$ 87,335	$ 196,234	$ 132,181
Earnings per share attributable to WESCO International, Inc.
Basic (in dollars per share)	$ 1.53	$ 1.42	$ 3.91	$ 3.60
Diluted (in dollars per share)	$ 1.52	$ 1.41	$ 3.88	$ 3.56
Shipping and Handling [Member]
Cost of goods sold	$ 17,600	$ 18,800	$ 52,800	$ 55,600

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Statement of Cash Flows [Abstract]
Interest Paid, Including Capitalized Interest, Operating and Investing Activities	$ 38,347	$ 37,138
Operating Activities:
Net income	169,505	167,289
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	46,035	47,321
Deferred income taxes	4,621	12,194
Other operating activities, net	10,876	7,590
Changes in assets and liabilities
Increase (Decrease) in Accounts Receivable	122,903	104,215
Increase (Decrease) in Accounts and Other Receivables	(15,450)	(19,859)
Inventories, net	(1,500)	23,189
Prepaid expenses and other current assets	(20,720)	(22,088)
Accounts payable	46,902	18,235
Accrued payroll and benefit costs	(36,055)	2,788
Other current and noncurrent liabilities	4,453	2,298
Net cash provided by operating activities	116,664	174,460
Investing Activities:
Payments to Acquire Businesses, Gross	(27,742)	0
Capital expenditures	(30,323)	(23,749)
Other investing activities	4,575	3,609
Net cash used in investing activities	(53,490)	(20,140)
Financing Activities:
Proceeds from (Repayments of) Short-term Debt	(29,600)	(2,464)
Proceeds from issuance of long-term debt	1,105,397	994,323
Repayments of Long-term Debt	(927,410)	(1,081,323)
Other financing activities, net	175	(8,301)
Net cash used in financing activities	(18,082)	(124,820)
Payments for Repurchase of Common Stock	(152,735)	(27,055)
Payments of Debt Issuance Costs	(2,508)	0
Payment for Contingent Consideration Liability, Financing Activities	(11,401)	0
Effect of exchange rate on cash and cash equivalents	(3,275)	(4,693)
Net change in cash and cash equivalents	41,817	24,807
Cash and cash equivalents at the beginning of period	96,343	117,953
Cash and cash equivalents at the end of period	138,160	142,760
Income Taxes Paid	$ 54,044	$ 48,744

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)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax				$ (28,800)
Net Income (Loss) Attributable to Parent	169,210
Net Income (Loss) Attributable to Noncontrolling Interest	(1,921)
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)
Stock Issued, Value, Stock Options Exercised, Net of Tax Benefit (Expense)			$ 0			$ (230)
Adjustments to Additional Paid in Capital, Share-based Compensation and Exercise of Stock Options	(31)
Stock Granted, Value, Share-based Compensation, Net of Forfeitures	4,102
Adjustments Related to Tax Withholding for Share-based Compensation			$ 0				11	32
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period			(26,867)			(3,795)
Shares Paid for Tax Withholding for Share Based Compensation			0
Net Income (Loss) Attributable to Parent	57,940
Net Income (Loss) Attributable to Noncontrolling Interest					(267)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax				(28,715)
Common Stock, Value, Issued		$ 43	$ 591
Common Stock, Shares, Issued		4,339,431	59,144,569
Additional capital	1,005,897
Retained Earnings (Accumulated Deficit)	2,182,486
Treasury Stock, Value	$ (647,843)
ERROR in label resolution.	(16,384,969)
Stockholders' Equity Attributable to Noncontrolling Interest	$ (5,313)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(370,105)
Stock Issued, Value, Stock Options Exercised, Net of Tax Benefit (Expense)			$ 1			$ (119)
Adjustments to Additional Paid in Capital, Share-based Compensation and Exercise of Stock Options	14
Stock Granted, Value, Share-based Compensation, Net of Forfeitures	4,118
ERROR in label resolution.								(3,750)
Adjustments Related to Tax Withholding for Share-based Compensation			$ 0				(8)	(57)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period			(8,990)			(1,976)
Shares Paid for Tax Withholding for Share Based Compensation			(749)
Net Income (Loss) Attributable to Parent	66,849
Treasury Stock, Value, Acquired, Cost Method	$ (21,250)
Treasury Stock, Shares, Acquired	(351,821)
Net Income (Loss) Attributable to Noncontrolling Interest	$ (204)				(203)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax				20,486
Common Stock, Value, Issued		$ 43	$ 592
Common Stock, Shares, Issued		4,339,431	59,152,810
Additional capital	1,006,222
Retained Earnings (Accumulated Deficit)	2,249,327
Treasury Stock, Value	$ (669,212)
ERROR in label resolution.	(16,738,766)
Stockholders' Equity Attributable to Noncontrolling Interest	$ (5,516)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(349,619)
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)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax				22,517
Net Income (Loss) Attributable to Parent	$ 170,329
Treasury Stock, Shares, Acquired	(3,455,584)
Net Income (Loss) Attributable to Noncontrolling Interest	$ (824)
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)
Stock Issued, Value, Stock Options Exercised, Net of Tax Benefit (Expense)			$ 0			$ (157)
Adjustments to Additional Paid in Capital, Share-based Compensation and Exercise of Stock Options	6
Stock Granted, Value, Share-based Compensation, Net of Forfeitures	5,150
ERROR in label resolution.								(22,500)
Adjustments Related to Tax Withholding for Share-based Compensation			$ 0				4	(1)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period			(20,831)			(3,029)
Shares Paid for Tax Withholding for Share Based Compensation			(19)
Net Income (Loss) Attributable to Parent	63,464
Treasury Stock, Value, Acquired, Cost Method	$ (127,500)
Treasury Stock, Shares, Acquired	(2,394,816)
Net Income (Loss) Attributable to Noncontrolling Interest					(249)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax				20,244
Common Stock, Value, Issued		$ 43	$ 593
Common Stock, Shares, Issued		4,339,431	59,292,704
Additional capital	$ 998,218
Retained Earnings (Accumulated Deficit)	2,412,768
Treasury Stock, Value	$ (904,873)
ERROR in label resolution.	(21,154,343)
Stockholders' Equity Attributable to Noncontrolling Interest	$ (6,252)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(365,674)
Stock Issued, Value, Stock Options Exercised, Net of Tax Benefit (Expense)			$ 0			$ (5)
Adjustments to Additional Paid in Capital, Share-based Compensation and Exercise of Stock Options	0
Stock Granted, Value, Share-based Compensation, Net of Forfeitures	4,426
ERROR in label resolution.								32,257
Adjustments Related to Tax Withholding for Share-based Compensation			$ 0				$ (4)	$ (13)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period			(1,983)			(94)
Shares Paid for Tax Withholding for Share Based Compensation			(190)
Net Income (Loss) Attributable to Parent	64,495
Treasury Stock, Value, Acquired, Cost Method	$ (32,257)
Treasury Stock, Shares, Acquired	(695,496)
Net Income (Loss) Attributable to Noncontrolling Interest	$ (156)				$ (156)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax				$ (16,856)
Common Stock, Value, Issued		$ 43	$ 593
Common Stock, Shares, Issued		4,339,431	59,294,497
Additional capital	1,034,888
Retained Earnings (Accumulated Deficit)	2,477,259
Treasury Stock, Value	$ (937,135)
ERROR in label resolution.	(21,849,933)
Stockholders' Equity Attributable to Noncontrolling Interest	$ (6,408)
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (382,530)

ORGANIZATION	9 Months Ended
ORGANIZATION	Sep. 30, 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 11 distribution centers located in the United States and Canada.

ACCOUNTING POLICIES	9 Months Ended
ACCOUNTING POLICIES	Sep. 30, 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 September 30, 2019, the unaudited Condensed Consolidated Statements of Income and Comprehensive Income, and the unaudited Condensed Consolidated Statements of Stockholders' Equity for the three and nine months ended September 30, 2019 and 2018, and the unaudited Condensed Consolidated Statements of Cash Flows for the nine months ended September 30, 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. Reclassifications The Condensed Consolidated Statement of Cash Flows for the nine months ended September 30, 2018 includes certain reclassifications to previously reported amounts to conform to the current period presentation. 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 Statements of Income and Comprehensive Income or Consolidated Statements of Cash Flows for the three and nine months ended September 30, 2019, respectively. 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 is currently evaluating the impact of adopting this ASU, but does not expect that it will 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

9 Months Ended

Sep. 30, 2019

Business Combinations [Abstract]

Mergers, Acquisitions and Dispositions Disclosures [Text Block]

5. ACQUISITIONS

The following table sets forth the consideration paid for acquisitions:



	Nine Months Ended
	September 30
	2019
	(In thousands)
Fair value of assets acquired	$	36,188
Fair value of liabilities assumed	8,446
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 $5.9 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				Nine Months Ended
	September 30				September 30
(In thousands)	2019		2018		2019		2018
Industrial	$	755,129	$	723,869	$	2,253,974	$	2,243,590
Construction	714,589		686,165		2,052,061		2,007,708
Utility	357,527		345,937		1,012,726		998,438
Commercial, Institutional and Government	320,865		311,274		940,704		915,418
Total by end market	$	2,148,110	$	2,067,245	$	6,259,465	$	6,165,154



	Three Months Ended				Nine Months Ended
	September 30				September 30
(In thousands)	2019		2018		2019		2018
United States	$	1,601,962	$	1,525,393	$	4,679,251	$	4,571,533
Canada ⁽¹⁾	431,233		429,830		1,230,855		1,234,600
Other International ⁽¹⁾	114,915		112,022		349,359		359,021
Total by geography	$	2,148,110	$	2,067,245	$	6,259,465	$	6,165,154


⁽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 September 30, 2019 and December 31, 2018, $11.0 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 September 30, 2019 and 2018 by approximately $26.3 million and $25.1 million, respectively, and by approximately $80.1 million and $74.5 million for the nine months ended September 30, 2019 and 2018, 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 $17.6 million and $18.8 million for the three months ended September 30, 2019 and 2018, respectively, and $52.8 million and $55.6 million for the nine months ended September 30, 2019 and 2018, respectively.

STOCK-BASED COMPENSATION

9 Months Ended

Sep. 30, 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 awards 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: 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: the three-year average growth rate of the Company’s fully diluted earnings per share and the three-year cumulative return on net assets. From 2015 to 2017, the two equally-weighted performance-based award metrics were the three-year average growth rate of WESCO's net income and WESCO's total stockholder return in relation to the total stockholder return of a select group of peer companies over a three-year period.

During the three and nine months ended September 30, 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				Nine Months Ended
	September 30, 2019		September 30, 2018		September 30, 2019		September 30, 2018
Stock-settled stock appreciation rights granted	—		9,415		213,618		509,046
Weighted-average fair value	$	—	$	17.40	$	16.36	$	18.38

Restricted stock units granted	6,256		2,686		181,800		119,457
Weighted-average fair value	$	47.95	$	61.41	$	54.41	$	62.72

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			Nine Months Ended
	September 30, 2019	September 30, 2018		September 30, 2019		September 30, 2018
Risk free interest rate	n/a	2.8	%	2.5	%	2.5	%
Expected life (in years)	n/a	5		5		5
Expected volatility	n/a	28	%	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 nine months ended September 30, 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	(108,022	)	34.84
Forfeited	(87,351	)	65.96
Outstanding at September 30, 2019	2,369,878		59.71		5.8	$	4,948
Exercisable at September 30, 2019	1,749,201		$	59.00	4.9	$	4,948

The following table sets forth a summary of time-based restricted stock units and related information for the nine months ended September 30, 2019:



	Awards		Weighted- Average Fair Value
Unvested at December 31, 2018	327,798		$	57.87
Granted	181,800		54.41
Vested	(118,560	)	44.58
Forfeited	(17,736	)	59.57
Unvested at September 30, 2019	373,302		$	60.25

Performance shares are awards for which the vesting will occur based on market or performance conditions. The following table sets forth a summary of performance-based awards for the nine months ended September 30, 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	(44,769	)	52.15
Unvested at September 30, 2019	195,305		$	60.24

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 177,798 shares of performance-based awards in the table above is dependent upon the achievement of certain performance targets, including 77,856 that are dependent upon the three-year average growth rate of WESCO's net income, 19,797 that are dependent upon the three-year average growth rate of the Company's fully diluted earnings per share, and 80,145 that are based upon the three-year cumulative return on net assets. These awards are accounted for as awards with performance conditions; compensation cost is recognized over the performance period based upon WESCO's determination of whether it is probable that the performance targets will be achieved.

WESCO recognized $4.4 million and $4.1 million of non-cash stock-based compensation expense, which is included in selling, general and administrative expenses, for the three months ended September 30, 2019 and 2018, respectively. WESCO recognized $14.2 million and $12.1 million of non-cash stock-based compensation expense, which is included in selling, general and administrative expenses, for the nine months ended September 30, 2019 and 2018, respectively. As of September 30, 2019, there was $24.9 million of total unrecognized compensation cost related to non-vested stock-based compensation arrangements for all awards previously made, of which approximately $4.8 million is expected to be recognized over the remainder of 2019, $12.7 million in 2020, $6.7 million in 2021 and $0.7 million in 2022.

EARNINGS PER SHARE

9 Months Ended

Sep. 30, 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				Nine Months Ended
	September 30				September 30
(In thousands, except per share data)	2019		2018		2019		2018
Net income attributable to WESCO International	$	64,495	$	66,849	$	170,329	$	169,210
Weighted-average common shares outstanding used in computing basic earnings per share	42,100		47,010		43,545		47,044
Common shares issuable upon exercise of dilutive equity awards	278		476		355		503
Weighted-average common shares outstanding and common share equivalents used in computing diluted earnings per share	42,378		47,486		43,900		47,547
Earnings per share attributable to WESCO International
Basic	$	1.53	$	1.42	$	3.91	$	3.60
Diluted	$	1.52	$	1.41	$	3.88	$	3.56

For the three and nine months ended September 30, 2019, the computation of diluted earnings per share attributable to WESCO International excluded approximately 1.8 million of stock-based awards. For the three and nine months ended September 30, 2018, the computation of diluted earnings per share attributable to WESCO International excluded stock-based awards of approximately 1.7 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 May 7, 2019, the Company entered into an accelerated stock repurchase agreement with a financial institution to repurchase additional shares of its common stock. In exchange for an up-front cash payment of $150.0 million, the Company received a total of 3,090,312 shares, of which 695,496 were received during the three months ended September 30, 2019. WESCO funded the repurchase primarily with borrowings under its accounts receivable securitization facility. For the nine months ended September 30, 2019, the Company received a total of 3,455,584 shares, of which 365,272 were received upon the settlement of an accelerated stock repurchase agreement entered into on November 6, 2018.

The total number of shares ultimately delivered under an accelerated stock repurchase transaction is determined by the average of the volume-weighted-average price of the Company's common stock for each exchange business day during the respective settlement valuation periods. For purposes of computing earnings per share for the three and nine months ended September 30, 2019, share repurchases have been reflected as a reduction to common shares outstanding on the respective delivery dates.

EMPLOYEE BENEFIT PLANS

9 Months Ended

Sep. 30, 2019

Retirement Benefits [Abstract]

EMPLOYEE BENEFIT PLANS

. EMPLOYEE BENEFIT PLANS

A majority of WESCO’s employees are covered by defined contribution retirement savings plans for their services rendered subsequent to WESCO’s formation. WESCO also offers a deferred compensation plan for select individuals. For U.S. participants, WESCO 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 nine months ended September 30, 2019 and 2018, WESCO incurred charges of $24.7 million and $33.5 million, respectively, for all such plans. Contributions are made in cash to employee retirement savings plan accounts. The deferred compensation plan is an unfunded plan. As of September 30, 2019 and December 31, 2018, the Company's obligation under the deferred compensation plan was $23.8 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 and nine months ended September 30, 2019, the Company contributed $0.1 million and $0.3 million, respectively, to the SERP.

The following table sets forth the components of net periodic benefit costs for the defined benefit plans:



	Three Months Ended						Nine Months Ended
	September 30						September 30
(In thousands)	2019			2018			2019			2018
Service cost	$	1,158		$	1,296		$	3,446		$	3,955
Interest cost	1,098			1,026			3,267			3,131
Expected return on plan assets	(1,433		)	(1,482		)	(4,265		)	(4,522		)
Recognized actuarial gain	(16		)	(11		)	(47		)	(35		)
Net periodic benefit cost	$	807		$	829		$	2,401		$	2,529

The service cost of $1.2 million and $1.3 million for the three months ended September 30, 2019 and 2018, respectively, and $3.4 million and $4.0 million for the nine months ended September 30, 2019 and 2018, respectively, was reported as a component of selling, general and administrative expenses. The other components of net periodic benefit cost totaling a net benefit of $0.4 million and $0.5 million for the three months ended September 30, 2019 and 2018, respectively, and $1.0 million and $1.4 million for the nine months ended September 30, 2019 and 2018, respectively, were presented as a component of net interest and other.

COMMITMENTS AND CONTINGENCIES	9 Months Ended
COMMITMENTS AND CONTINGENCIES	Sep. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	12. 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 September 30, 2019, WESTEC had an outstanding loan balance of $6.4 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 September 30, 2019.

INCOME TAXES	9 Months Ended
INCOME TAXES	Sep. 30, 2019
Income Tax Disclosure [Abstract]
INCOME TAXES	13. INCOME TAXES The effective tax rate for the three and nine months ended September 30, 2019 was 19.8% and 21.0%, respectively. The effective tax rate for the three and nine months ended September 30, 2018 was 17.2% and 19.3%, 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 effective tax rates for the current year periods are higher than the prior year periods primarily due to the full application of the international provisions of U.S. tax reform, as well as the discrete effect of accruing taxes attributable to the undistributed earnings of operations in China that are expected to be remitted in the future. The total amount of unrecognized tax benefits was reduced from $1.3 million to $0.1 million during the nine months ended September 30, 2019 due to the resolution of transfer pricing matters associated with the Canadian taxing authority.

OTHER FINANCIAL INFORMATION

9 Months Ended

Sep. 30, 2019

Condensed Financial Information [Abstract]

OTHER FINANCIAL INFORMATION

14. CONDENSED CONSOLIDATING FINANCIAL INFORMATION

WESCO Distribution has outstanding $500 million in aggregate principal amount of 5.375% Senior Notes due 2021 (the "2021 Notes") and $350 million in aggregate principal amount of 5.375% Senior Notes due 2024 (the "2024 Notes"). The 2021 Notes and 2024 Notes are unsecured senior obligations of WESCO Distribution and are fully and unconditionally guaranteed on a senior unsecured basis by WESCO International.

Condensed consolidating financial information for WESCO International, WESCO Distribution and the non-guarantor subsidiaries is presented in the following tables.



	Condensed Consolidating Balance Sheet
	September 30, 2019

(In thousands)	WESCO International, Inc.		WESCO Distribution, Inc.		Non-Guarantor Subsidiaries			Consolidating and Eliminating Entries			Consolidated
Cash and cash equivalents	$	—	$	37,889	$	100,271		$	—		$	138,160
Trade accounts receivable, net	—		—		1,315,026			—			1,315,026
Inventories	—		437,470		524,527			—			961,997
Prepaid expenses and other current assets	1,123		27,376		136,719			(1,921		)	163,297
Total current assets	1,123		502,735		2,076,543			(1,921		)	2,578,480
Intercompany receivables, net	—		—		2,543,978			(2,543,978		)	—
Property, buildings and equipment, net	—		76,980		97,479			—			174,459
Operating lease assets	—		146,247		91,005			—			237,252
Intangible assets, net	—		1,658		291,835			—			293,493
Goodwill	—		257,623		1,488,448			—			1,746,071
Investments in affiliates	3,383,537		5,318,786		—			(8,702,323		)	—
Other assets	—		854		16,802			—			17,656
Total assets	$	3,384,660	$	6,304,883	$	6,606,090		$	(11,248,222	)	$	5,047,411

Accounts payable	$	—	$	418,502	$	431,082		$	—		$	849,584
Short-term debt	—		—		25,561			—			25,561
Other current liabilities	—		69,505		161,795			(1,921		)	229,379
Total current liabilities	—		488,007		618,438			(1,921		)	1,104,524
Intercompany payables, net	1,191,542		1,352,436		—			(2,543,978		)	—
Long-term debt, net	—		856,992		489,341			—			1,346,333
Operating lease liabilities	—		116,336		65,708			—			182,044
Other noncurrent liabilities	—		107,575		120,225			—			227,800
Total WESCO International stockholders' equity	2,193,118		3,383,537		5,318,786			(8,702,323		)	2,193,118
Noncontrolling interests	—		—		(6,408		)	—			(6,408		)
Total liabilities and stockholders’ equity	$	3,384,660	$	6,304,883	$	6,606,090		$	(11,248,222	)	$	5,047,411



	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
	September 30, 2019

(In thousands)	WESCO International, Inc.			WESCO Distribution, Inc.			Non-Guarantor Subsidiaries			Consolidating and Eliminating Entries			Consolidated
Net sales	$	—		$	939,909		$	1,244,847		$	(36,646	)	$	2,148,110
Cost of goods sold (excluding depreciation and
amortization)	—			768,200			1,016,359			(36,646		)	1,747,913
Selling, general and administrative expenses	—			146,925			143,927			—			290,852
Depreciation and amortization	—			4,834			10,778			—			15,612
Results of affiliates’ operations	64,339			58,725			—			(123,064		)	—
Net interest and other	—			12,944			564			—			13,508
Income tax expense	—			1,392			14,494			—			15,886
Net income	64,339			64,339			58,725			(123,064		)	64,339
Net loss attributable to noncontrolling interests	—			—			(156		)	—			(156		)
Net income attributable to WESCO International	$	64,339		$	64,339		$	58,881		$	(123,064	)	$	64,495
Other comprehensive income:
Foreign currency translation adjustments	(16,856		)	(16,856		)	(16,856		)	33,712			(16,856		)
Comprehensive income attributable to WESCO International	$	47,483		$	47,483		$	42,025		$	(89,352	)	$	47,639



	Condensed Consolidating Statement of Income and Comprehensive Income
	Nine Months Ended
	September 30, 2019

(In thousands)	WESCO International, Inc.		WESCO Distribution, Inc.		Non-Guarantor Subsidiaries			Consolidating and Eliminating Entries			Consolidated
Net sales	$	—	$	2,736,224	$	3,643,193		$	(119,952	)	$	6,259,465
Cost of goods sold (excluding depreciation and
amortization)	—		2,220,792		2,966,959			(119,952		)	5,067,799
Selling, general and administrative expenses	—		445,487		437,735			—			883,222
Depreciation and amortization	—		13,861		32,174			—			46,035
Results of affiliates’ operations	169,505		155,100		—			(324,605		)	—
Net interest and other	—		37,856		10,078			—			47,934
Income tax expense	—		3,823		41,147			—			44,970
Net income	169,505		169,505		155,100			(324,605		)	169,505
Net loss attributable to noncontrolling interests	—		—		(824		)	—			(824		)
Net income attributable to WESCO International	$	169,505	$	169,505	$	155,924		$	(324,605	)	$	170,329
Other comprehensive income:
Foreign currency translation adjustments	25,905		25,905		25,905			(51,810		)	25,905
Comprehensive income attributable to WESCO International	$	195,410	$	195,410	$	181,829		$	(376,415	)	$	196,234



	Condensed Consolidating Statement of Income and Comprehensive Income
	Three Months Ended
	September 30, 2018

(In thousands)	WESCO International, Inc.		WESCO Distribution, Inc.		Non-Guarantor Subsidiaries			Consolidating and Eliminating Entries			Consolidated
Net sales	$	—	$	899,994	$	1,206,174		$	(38,923	)	$	2,067,245
Cost of goods sold (excluding depreciation and
amortization)	—		727,052		981,908			(38,923		)	1,670,037
Selling, general and administrative expenses	—		149,390		134,683			—			284,073
Depreciation and amortization	—		4,475		11,143			—			15,618
Results of affiliates’ operations	66,645		61,771		—			(128,416		)	—
Net interest and other	—		13,127		3,923			—			17,050
Income tax expense	—		1,076		12,746			—			13,822
Net income	66,645		66,645		61,771			(128,416		)	66,645
Net loss attributable to noncontrolling interests	—		—		(204		)	—			(204		)
Net income attributable to WESCO International	$	66,645	$	66,645	$	61,975		$	(128,416	)	$	66,849
Other comprehensive income:
Foreign currency translation adjustments	20,486		20,486		20,486			(40,972		)	20,486
Comprehensive income attributable to WESCO International	$	87,131	$	87,131	$	82,461		$	(169,388	)	$	87,335



	Condensed Consolidating Statement of Income and Comprehensive Income
	Nine Months Ended
	September 30, 2018

(In thousands)	WESCO International, Inc.			WESCO Distribution, Inc.			Non-Guarantor Subsidiaries			Consolidating and Eliminating Entries			Consolidated
Net sales	$	—		$	2,703,468		$	3,578,653		$	(116,967	)	$	6,165,154
Cost of goods sold (excluding depreciation and
amortization)	—			2,189,683			2,915,387			(116,967		)	4,988,103
Selling, general and administrative expenses	—			447,437			420,353			—			867,790
Depreciation and amortization	—			13,749			33,572			—			47,321
Results of affiliates’ operations	167,289			158,093			—			(325,382		)	—
Net interest and other	—			41,202			13,372			—			54,574
Income tax expense	—			2,201			37,876			—			40,077
Net income	167,289			167,289			158,093			(325,382		)	167,289
Net loss attributable to noncontrolling interests	—			—			(1,921		)	—			(1,921		)
Net income attributable to WESCO International	$	167,289		$	167,289		$	160,014		$	(325,382	)	$	169,210
Other comprehensive loss:
Foreign currency translation adjustments	(37,029		)	(37,029		)	(37,029		)	74,058			(37,029		)
Comprehensive income attributable to WESCO International	$	130,260		$	130,260		$	122,985		$	(251,324	)	$	132,181



	Condensed Consolidating Statement of Cash Flows
	Nine Months Ended
	September 30, 2019

(In thousands)	WESCO International, Inc.			WESCO Distribution, Inc.			Non-Guarantor Subsidiaries			Consolidating and Eliminating Entries			Consolidated
Net cash provided by (used in) operating activities	$	9,480		$	210,707		$	(103,523	)	$	—		$	116,664
Investing activities:
Capital expenditures	—			(13,269		)	(17,054		)	—			(30,323		)
Acquisition payments	—			(27,742		)	—			—			(27,742		)
Dividends received from subsidiaries	—			67,065			—			(67,065		)	—
Other	—			(210,320		)	4,575			210,320			4,575
Net cash used in investing activities	—			(184,266		)	(12,479		)	143,255			(53,490		)
Financing activities:
Borrowings	143,255			333,418			856,464			(210,320		)	1,122,817
Repayments	—			(344,167		)	(630,263		)	—			(974,430		)
Repurchases of common stock	(152,735		)	—			—			—			(152,735		)
Dividends paid by subsidiaries	—			—			(67,065		)	67,065			—
Other	—			(13,734		)	—			—			(13,734		)
Net cash (used in) provided by financing activities	(9,480		)	(24,483		)	159,136			(143,255		)	(18,082		)
Effect of exchange rate changes on cash and cash equivalents	—			—			(3,275		)	—			(3,275		)
Net change in cash and cash equivalents	—			1,958			39,859			—			41,817
Cash and cash equivalents at the beginning of period	—			35,931			60,412			—			96,343
Cash and cash equivalents at the end of period	$	—		$	37,889		$	100,271		$	—		$	138,160



	Condensed Consolidating Statement of Cash Flows
	Nine Months Ended
	September 30, 2018

(In thousands)	WESCO International, Inc.			WESCO Distribution, Inc.			Non-Guarantor Subsidiaries			Consolidating and Eliminating Entries			Consolidated
Net cash provided by operating activities	$	14,198		$	62,439		$	97,823		$	—		$	174,460
Investing activities:
Capital expenditures	—			(12,831		)	(10,918		)	—			(23,749		)
Dividends received from subsidiaries	—			118,271			—			(118,271		)	—
Other	—			(81,128		)	3,609			81,128			3,609
Net cash provided by (used in) investing activities	—			24,312			(7,309		)	(37,143		)	(20,140		)
Financing activities:
Borrowings	12,857			246,323			933,046			(81,128		)	1,111,098
Repayments	—			(318,323		)	(882,239		)	—			(1,200,562		)
Repurchases of common stock	(27,055		)	—			—			—			(27,055		)
Dividends paid by subsidiaries	—			—			(118,271		)	118,271			—
Other	—			(8,301		)	—			—			(8,301		)
Net cash used in financing activities	(14,198		)	(80,301		)	(67,464		)	37,143			(124,820		)
Effect of exchange rate changes on cash and cash equivalents	—			—			(4,693		)	—			(4,693		)
Net change in cash and cash equivalents	—			6,450			18,357			—			24,807
Cash and cash equivalents at the beginning of period	—			50,602			67,351			—			117,953
Cash and cash equivalents at the end of period	$	—		$	57,052		$	85,708		$	—		$	142,760

Subsequent Events SUBSEQUENT EVENTS (Notes)	9 Months Ended
Subsequent Events SUBSEQUENT EVENTS (Notes)	Sep. 30, 2019
Subsequent Events [Abstract]
Subsequent Events [Text Block]	15. 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.

Debt (Notes)	9 Months Ended
Debt (Notes)	Sep. 30, 2019
Debt Instrument [Line Items]
Debt Disclosure [Text Block]	9. DEBT Revolving Credit Facility On September 26, 2019, WESCO International, WESCO Distribution and certain other subsidiaries of the Company entered into a $600 million revolving credit facility (the “Revolving Credit Facility”) as a replacement of its existing revolving credit facility entered into on September 24, 2015. The Revolving Credit Facility contains a letter of credit sub-facility of up to $125 million, pursuant to the terms and conditions of a Third Amended and Restated Credit Agreement, dated as of September 26, 2019 (the “Credit Agreement”). The Revolving Credit Facility contains an accordion feature allowing WESCO Distribution to request increases to the borrowing commitments under the Revolving Credit Facility of up to $200 million in the aggregate, subject to customary conditions. The Revolving Credit Facility matures in September 2024 and is collateralized by (i) substantially all assets of WESCO Distribution and its subsidiaries which are party to the Credit Agreement, other than, among other things, real property and accounts receivable sold or intended to be sold pursuant to WESCO Distribution’s accounts receivable securitization facility, and (ii) substantially all assets of WESCO Canada and the other Canadian Borrowers, other than, among other things, real property, in each case, subject to customary exceptions and limitations. The obligations of WESCO Distribution and the other U.S. Borrowers under the Revolving Credit Facility have been guaranteed by the Company and certain of WESCO Distribution’s subsidiaries. The obligations of WESCO Canada and the other Canadian Borrowers under the Revolving Credit Facility have been guaranteed by certain subsidiaries of WESCO Canada and the other Canadian Borrowers. The applicable interest rate for borrowings under the Revolving Credit Facility includes interest rate spreads based on available borrowing capacity that range between 1.25% and 1.50% for LIBOR-based borrowings and 0.25% and 0.50% for prime rate-based borrowings. The Credit Agreement requires compliance with conditions precedent that must be satisfied prior to any borrowing as well as ongoing compliance with certain customary affirmative and negative covenants. The Credit Agreement contains customary events of default. Accounts Receivable Securitization Facility On September 26, 2019, WESCO Distribution amended its accounts receivable securitization facility (the “Receivables Facility”) pursuant to the terms and conditions of a Ninth Amendment to the Fourth Amended and Restated Receivables Purchase Agreement, dated as of September 26, 2019 (the “Receivables Amendment”), by and among WESCO Receivables Corp. (“WESCO Receivables”), WESCO Distribution, the various purchaser groups from time to time party thereto and PNC Bank, National Association, as Administrator. The Receivables Amendment amends the amended and restated receivables purchase agreement entered into on September 24, 2015 (the “Existing Receivables Purchase Agreement” and as amended by the Receivables Amendment, the “Receivables Purchase Agreement”). The Receivables Amendment increased the purchase limit under the Existing Receivables Purchase Agreement from $550 million to $600 million, with the opportunity to exercise an accordion feature which permits increases in the purchase limit of up to $200 million, extended the term of the Receivables Facility to September 26, 2022 and added and amended certain defined terms. The interest rate spread and commitment fee of the Receivables Facility remains 0.95% and 0.45%, respectively. Under the Receivables Facility, WESCO sells, on a continuous basis, an undivided interest in all domestic accounts receivable to WESCO Receivables, a wholly owned special purpose entity (the “SPE”). The SPE sells, without recourse, a senior undivided interest in the receivables to financial institutions for cash while maintaining a subordinated undivided interest in the receivables, in the form of overcollateralization. Since WESCO maintains control of the transferred receivables, the transfers do not qualify for “sale” treatment. As a result, the transferred receivables remain on the balance sheet, and WESCO recognizes the related secured borrowing. WESCO has agreed to continue servicing the sold receivables for the third-party conduits and financial institutions at market rates; accordingly, no servicing asset or liability has been recorded.

GOODWILL (Notes)

9 Months Ended

Sep. 30, 2019

Goodwill [Line Items]

Goodwill Disclosure [Text Block]

6. GOODWILL

The following table sets forth the changes in the carrying value of goodwill:



	Nine Months Ended
	September 30
(In thousands)	2019
Beginning balance January 1	$	1,722,603
Foreign currency exchange rate changes	17,522
Additions to goodwill for acquisitions	5,946
Ending balance September 30	$	1,746,071

NET INTEREST AND OTHER (Notes)	9 Months Ended
NET INTEREST AND OTHER (Notes)	Sep. 30, 2019
Other Income and Expenses [Abstract]
Other Nonoperating Income and Expense [Text Block]	11. 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 September 30, 2019 and December 31, 2018.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

LEASES (Notes)

9 Months Ended

Sep. 30, 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 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 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 September 30, 2019 as a component of property, buildings and equipment, current portion of long-term debt and long-term debt, 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)	September 30, 2019
Operating lease assets	$	237,252

Current operating lease liabilities	61,114
Noncurrent operating lease liabilities	182,044
Total operating lease liabilities	$	243,158

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 periods presented:



	Three Months Ended		Nine Months Ended
	September 30		September 30
(In thousands)	2019		2019
Operating lease cost	$	18,605	$	54,879
Short-term lease cost	23		56
Variable lease cost	5,335		17,119
Total lease cost	$	23,963	$	72,054

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:



	Nine Months Ended
	September 30
(In thousands)	2019
Operating cash flows from operating leases	$	48,484
Right-of-use assets obtained in exchange for new operating lease liabilities	48,622

As of September 30, 2019, the weighted-average remaining lease term for operating leases was 5.4 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 September 30, 2019:



	(In thousands)
2019	$	18,464
2020	68,791
2021	58,134
2022	44,780
2023	34,872
Thereafter	51,749
Total undiscounted operating lease payments	276,790
Less: interest	(33,632		)
Total operating lease liabilities	$	243,158

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)	9 Months Ended
ACCOUNTING POLICIES (Policies)	Sep. 30, 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 September 30, 2019, the unaudited Condensed Consolidated Statements of Income and Comprehensive Income, and the unaudited Condensed Consolidated Statements of Stockholders' Equity for the three and nine months ended September 30, 2019 and 2018, and the unaudited Condensed Consolidated Statements of Cash Flows for the nine months ended September 30, 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 Statements of Income and Comprehensive Income or Consolidated Statements of Cash Flows for the three and nine months ended September 30, 2019, respectively. 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.
Reclassifications [Text Block]	Reclassifications The Condensed Consolidated Statement of Cash Flows for the nine months ended September 30, 2018 includes certain reclassifications to previously reported amounts to conform to the current period presentation.
Fair Value of Financial Instruments	11. 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 September 30, 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 is currently evaluating the impact of adopting this ASU, but does not expect that it will 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.

- Definition

+ References + Details

COMMITMENTS AND CONTINGENCIES Guarantee (Policies)	9 Months Ended
COMMITMENTS AND CONTINGENCIES Guarantee (Policies)	Sep. 30, 2019
Guarantees and Product Warranties [Abstract]
Guarantees [Text Block]	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 September 30, 2019, WESTEC had an outstanding loan balance of $6.4 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 September 30, 2019.

ACQUISITIONS (Tables)

9 Months Ended

Sep. 30, 2019

Acquisitions [Abstract]

Schedule of Business Acquisitions, by Acquisition [Table Text Block]



	Nine Months Ended
	September 30
	2019
	(In thousands)
Fair value of assets acquired	$	36,188
Fair value of liabilities assumed	8,446
Cash paid for acquisitions	$	27,742

STOCK-BASED COMPENSATION (Tables)

9 Months Ended

Sep. 30, 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]



	Three Months Ended				Nine Months Ended
	September 30, 2019		September 30, 2018		September 30, 2019		September 30, 2018
Stock-settled stock appreciation rights granted	—		9,415		213,618		509,046
Weighted-average fair value	$	—	$	17.40	$	16.36	$	18.38

Restricted stock units granted	6,256		2,686		181,800		119,457
Weighted-average fair value	$	47.95	$	61.41	$	54.41	$	62.72

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 nine months ended September 30, 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	(108,022	)	34.84
Forfeited	(87,351	)	65.96
Outstanding at September 30, 2019	2,369,878		59.71		5.8	$	4,948
Exercisable at September 30, 2019	1,749,201		$	59.00	4.9	$	4,948

Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block]

The following table sets forth a summary of time-based restricted stock units and related information for the nine months ended September 30, 2019:



	Awards		Weighted- Average Fair Value
Unvested at December 31, 2018	327,798		$	57.87
Granted	181,800		54.41
Vested	(118,560	)	44.58
Forfeited	(17,736	)	59.57
Unvested at September 30, 2019	373,302		$	60.25

Schedule of Nonvested Performance-based Units Activity [Table Text Block]

The following table sets forth a summary of performance-based awards for the nine months ended September 30, 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	(44,769	)	52.15
Unvested at September 30, 2019	195,305		$	60.24

Stock Appreciation Rights (SARs) [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

The fair value of stock-settled stock appreciation rights was estimated using the following weighted-average assumptions:



	Three Months Ended			Nine Months Ended
	September 30, 2019	September 30, 2018		September 30, 2019		September 30, 2018
Risk free interest rate	n/a	2.8	%	2.5	%	2.5	%
Expected life (in years)	n/a	5		5		5
Expected volatility	n/a	28	%	29	%	28	%

EARNINGS PER SHARE (Tables)

9 Months Ended

Sep. 30, 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				Nine Months Ended
	September 30				September 30
(In thousands, except per share data)	2019		2018		2019		2018
Net income attributable to WESCO International	$	64,495	$	66,849	$	170,329	$	169,210
Weighted-average common shares outstanding used in computing basic earnings per share	42,100		47,010		43,545		47,044
Common shares issuable upon exercise of dilutive equity awards	278		476		355		503
Weighted-average common shares outstanding and common share equivalents used in computing diluted earnings per share	42,378		47,486		43,900		47,547
Earnings per share attributable to WESCO International
Basic	$	1.53	$	1.42	$	3.91	$	3.60
Diluted	$	1.52	$	1.41	$	3.88	$	3.56

EMPLOYEE BENEFIT PLANS Schedule of Net Benefit Costs (Tables)

9 Months Ended

Sep. 30, 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						Nine Months Ended
	September 30						September 30
(In thousands)	2019			2018			2019			2018
Service cost	$	1,158		$	1,296		$	3,446		$	3,955
Interest cost	1,098			1,026			3,267			3,131
Expected return on plan assets	(1,433		)	(1,482		)	(4,265		)	(4,522		)
Recognized actuarial gain	(16		)	(11		)	(47		)	(35		)
Net periodic benefit cost	$	807		$	829		$	2,401		$	2,529

OTHER FINANCIAL INFORMATION (Tables)

9 Months Ended

Sep. 30, 2019

Condensed Balance Sheet Statements, Captions [Line Items]

Condensed Balance Sheet [Table Text Block]



	Condensed Consolidating Balance Sheet
	September 30, 2019

(In thousands)	WESCO International, Inc.		WESCO Distribution, Inc.		Non-Guarantor Subsidiaries			Consolidating and Eliminating Entries			Consolidated
Cash and cash equivalents	$	—	$	37,889	$	100,271		$	—		$	138,160
Trade accounts receivable, net	—		—		1,315,026			—			1,315,026
Inventories	—		437,470		524,527			—			961,997
Prepaid expenses and other current assets	1,123		27,376		136,719			(1,921		)	163,297
Total current assets	1,123		502,735		2,076,543			(1,921		)	2,578,480
Intercompany receivables, net	—		—		2,543,978			(2,543,978		)	—
Property, buildings and equipment, net	—		76,980		97,479			—			174,459
Operating lease assets	—		146,247		91,005			—			237,252
Intangible assets, net	—		1,658		291,835			—			293,493
Goodwill	—		257,623		1,488,448			—			1,746,071
Investments in affiliates	3,383,537		5,318,786		—			(8,702,323		)	—
Other assets	—		854		16,802			—			17,656
Total assets	$	3,384,660	$	6,304,883	$	6,606,090		$	(11,248,222	)	$	5,047,411

Accounts payable	$	—	$	418,502	$	431,082		$	—		$	849,584
Short-term debt	—		—		25,561			—			25,561
Other current liabilities	—		69,505		161,795			(1,921		)	229,379
Total current liabilities	—		488,007		618,438			(1,921		)	1,104,524
Intercompany payables, net	1,191,542		1,352,436		—			(2,543,978		)	—
Long-term debt, net	—		856,992		489,341			—			1,346,333
Operating lease liabilities	—		116,336		65,708			—			182,044
Other noncurrent liabilities	—		107,575		120,225			—			227,800
Total WESCO International stockholders' equity	2,193,118		3,383,537		5,318,786			(8,702,323		)	2,193,118
Noncontrolling interests	—		—		(6,408		)	—			(6,408		)
Total liabilities and stockholders’ equity	$	3,384,660	$	6,304,883	$	6,606,090		$	(11,248,222	)	$	5,047,411



	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 Condensed Income Statement (Tables)

9 Months Ended

Sep. 30, 2019

Condensed Income Statements, Captions [Line Items]

Condensed Income Statement [Table Text Block]



	Condensed Consolidating Statement of Income and Comprehensive Income
	Three Months Ended
	September 30, 2018

(In thousands)	WESCO International, Inc.		WESCO Distribution, Inc.		Non-Guarantor Subsidiaries			Consolidating and Eliminating Entries			Consolidated
Net sales	$	—	$	899,994	$	1,206,174		$	(38,923	)	$	2,067,245
Cost of goods sold (excluding depreciation and
amortization)	—		727,052		981,908			(38,923		)	1,670,037
Selling, general and administrative expenses	—		149,390		134,683			—			284,073
Depreciation and amortization	—		4,475		11,143			—			15,618
Results of affiliates’ operations	66,645		61,771		—			(128,416		)	—
Net interest and other	—		13,127		3,923			—			17,050
Income tax expense	—		1,076		12,746			—			13,822
Net income	66,645		66,645		61,771			(128,416		)	66,645
Net loss attributable to noncontrolling interests	—		—		(204		)	—			(204		)
Net income attributable to WESCO International	$	66,645	$	66,645	$	61,975		$	(128,416	)	$	66,849
Other comprehensive income:
Foreign currency translation adjustments	20,486		20,486		20,486			(40,972		)	20,486
Comprehensive income attributable to WESCO International	$	87,131	$	87,131	$	82,461		$	(169,388	)	$	87,335



	Condensed Consolidating Statement of Income and Comprehensive Income
	Nine Months Ended
	September 30, 2018

(In thousands)	WESCO International, Inc.			WESCO Distribution, Inc.			Non-Guarantor Subsidiaries			Consolidating and Eliminating Entries			Consolidated
Net sales	$	—		$	2,703,468		$	3,578,653		$	(116,967	)	$	6,165,154
Cost of goods sold (excluding depreciation and
amortization)	—			2,189,683			2,915,387			(116,967		)	4,988,103
Selling, general and administrative expenses	—			447,437			420,353			—			867,790
Depreciation and amortization	—			13,749			33,572			—			47,321
Results of affiliates’ operations	167,289			158,093			—			(325,382		)	—
Net interest and other	—			41,202			13,372			—			54,574
Income tax expense	—			2,201			37,876			—			40,077
Net income	167,289			167,289			158,093			(325,382		)	167,289
Net loss attributable to noncontrolling interests	—			—			(1,921		)	—			(1,921		)
Net income attributable to WESCO International	$	167,289		$	167,289		$	160,014		$	(325,382	)	$	169,210
Other comprehensive loss:
Foreign currency translation adjustments	(37,029		)	(37,029		)	(37,029		)	74,058			(37,029		)
Comprehensive income attributable to WESCO International	$	130,260		$	130,260		$	122,985		$	(251,324	)	$	132,181



	Condensed Consolidating Statement of Income and Comprehensive Income
	Nine Months Ended
	September 30, 2019

(In thousands)	WESCO International, Inc.		WESCO Distribution, Inc.		Non-Guarantor Subsidiaries			Consolidating and Eliminating Entries			Consolidated
Net sales	$	—	$	2,736,224	$	3,643,193		$	(119,952	)	$	6,259,465
Cost of goods sold (excluding depreciation and
amortization)	—		2,220,792		2,966,959			(119,952		)	5,067,799
Selling, general and administrative expenses	—		445,487		437,735			—			883,222
Depreciation and amortization	—		13,861		32,174			—			46,035
Results of affiliates’ operations	169,505		155,100		—			(324,605		)	—
Net interest and other	—		37,856		10,078			—			47,934
Income tax expense	—		3,823		41,147			—			44,970
Net income	169,505		169,505		155,100			(324,605		)	169,505
Net loss attributable to noncontrolling interests	—		—		(824		)	—			(824		)
Net income attributable to WESCO International	$	169,505	$	169,505	$	155,924		$	(324,605	)	$	170,329
Other comprehensive income:
Foreign currency translation adjustments	25,905		25,905		25,905			(51,810		)	25,905
Comprehensive income attributable to WESCO International	$	195,410	$	195,410	$	181,829		$	(376,415	)	$	196,234



	Condensed Consolidating Statement of Income and Comprehensive Income
	Three Months Ended
	September 30, 2019

(In thousands)	WESCO International, Inc.			WESCO Distribution, Inc.			Non-Guarantor Subsidiaries			Consolidating and Eliminating Entries			Consolidated
Net sales	$	—		$	939,909		$	1,244,847		$	(36,646	)	$	2,148,110
Cost of goods sold (excluding depreciation and
amortization)	—			768,200			1,016,359			(36,646		)	1,747,913
Selling, general and administrative expenses	—			146,925			143,927			—			290,852
Depreciation and amortization	—			4,834			10,778			—			15,612
Results of affiliates’ operations	64,339			58,725			—			(123,064		)	—
Net interest and other	—			12,944			564			—			13,508
Income tax expense	—			1,392			14,494			—			15,886
Net income	64,339			64,339			58,725			(123,064		)	64,339
Net loss attributable to noncontrolling interests	—			—			(156		)	—			(156		)
Net income attributable to WESCO International	$	64,339		$	64,339		$	58,881		$	(123,064	)	$	64,495
Other comprehensive income:
Foreign currency translation adjustments	(16,856		)	(16,856		)	(16,856		)	33,712			(16,856		)
Comprehensive income attributable to WESCO International	$	47,483		$	47,483		$	42,025		$	(89,352	)	$	47,639

OTHER FINANCIAL INFORMATION Condensed Cash Flow Statement (Tables)

9 Months Ended

Sep. 30, 2019

Condensed Cash Flow Statements, Captions [Line Items]

Condensed Cash Flow Statement [Table Text Block]



	Condensed Consolidating Statement of Cash Flows
	Nine Months Ended
	September 30, 2019

(In thousands)	WESCO International, Inc.			WESCO Distribution, Inc.			Non-Guarantor Subsidiaries			Consolidating and Eliminating Entries			Consolidated
Net cash provided by (used in) operating activities	$	9,480		$	210,707		$	(103,523	)	$	—		$	116,664
Investing activities:
Capital expenditures	—			(13,269		)	(17,054		)	—			(30,323		)
Acquisition payments	—			(27,742		)	—			—			(27,742		)
Dividends received from subsidiaries	—			67,065			—			(67,065		)	—
Other	—			(210,320		)	4,575			210,320			4,575
Net cash used in investing activities	—			(184,266		)	(12,479		)	143,255			(53,490		)
Financing activities:
Borrowings	143,255			333,418			856,464			(210,320		)	1,122,817
Repayments	—			(344,167		)	(630,263		)	—			(974,430		)
Repurchases of common stock	(152,735		)	—			—			—			(152,735		)
Dividends paid by subsidiaries	—			—			(67,065		)	67,065			—
Other	—			(13,734		)	—			—			(13,734		)
Net cash (used in) provided by financing activities	(9,480		)	(24,483		)	159,136			(143,255		)	(18,082		)
Effect of exchange rate changes on cash and cash equivalents	—			—			(3,275		)	—			(3,275		)
Net change in cash and cash equivalents	—			1,958			39,859			—			41,817
Cash and cash equivalents at the beginning of period	—			35,931			60,412			—			96,343
Cash and cash equivalents at the end of period	$	—		$	37,889		$	100,271		$	—		$	138,160



	Condensed Consolidating Statement of Cash Flows
	Nine Months Ended
	September 30, 2018

(In thousands)	WESCO International, Inc.			WESCO Distribution, Inc.			Non-Guarantor Subsidiaries			Consolidating and Eliminating Entries			Consolidated
Net cash provided by operating activities	$	14,198		$	62,439		$	97,823		$	—		$	174,460
Investing activities:
Capital expenditures	—			(12,831		)	(10,918		)	—			(23,749		)
Dividends received from subsidiaries	—			118,271			—			(118,271		)	—
Other	—			(81,128		)	3,609			81,128			3,609
Net cash provided by (used in) investing activities	—			24,312			(7,309		)	(37,143		)	(20,140		)
Financing activities:
Borrowings	12,857			246,323			933,046			(81,128		)	1,111,098
Repayments	—			(318,323		)	(882,239		)	—			(1,200,562		)
Repurchases of common stock	(27,055		)	—			—			—			(27,055		)
Dividends paid by subsidiaries	—			—			(118,271		)	118,271			—
Other	—			(8,301		)	—			—			(8,301		)
Net cash used in financing activities	(14,198		)	(80,301		)	(67,464		)	37,143			(124,820		)
Effect of exchange rate changes on cash and cash equivalents	—			—			(4,693		)	—			(4,693		)
Net change in cash and cash equivalents	—			6,450			18,357			—			24,807
Cash and cash equivalents at the beginning of period	—			50,602			67,351			—			117,953
Cash and cash equivalents at the end of period	$	—		$	57,052		$	85,708		$	—		$	142,760

GOODWILL (Tables)

9 Months Ended

Sep. 30, 2019

Goodwill [Line Items]

Schedule of Goodwill [Table Text Block]



	Nine Months Ended
	September 30
(In thousands)	2019
Beginning balance January 1	$	1,722,603
Foreign currency exchange rate changes	17,522
Additions to goodwill for acquisitions	5,946
Ending balance September 30	$	1,746,071

REVENUE (Tables)

9 Months Ended

Sep. 30, 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				Nine Months Ended
	September 30				September 30
(In thousands)	2019		2018		2019		2018
Industrial	$	755,129	$	723,869	$	2,253,974	$	2,243,590
Construction	714,589		686,165		2,052,061		2,007,708
Utility	357,527		345,937		1,012,726		998,438
Commercial, Institutional and Government	320,865		311,274		940,704		915,418
Total by end market	$	2,148,110	$	2,067,245	$	6,259,465	$	6,165,154



	Three Months Ended				Nine Months Ended
	September 30				September 30
(In thousands)	2019		2018		2019		2018
United States	$	1,601,962	$	1,525,393	$	4,679,251	$	4,571,533
Canada ⁽¹⁾	431,233		429,830		1,230,855		1,234,600
Other International ⁽¹⁾	114,915		112,022		349,359		359,021
Total by geography	$	2,148,110	$	2,067,245	$	6,259,465	$	6,165,154

⁽¹⁾

The prior period has been reclassified to conform to the current period presentation.

Revenue Recognition, Revenue Reductions [Policy Text Block]

LEASES (Tables)

9 Months Ended

Sep. 30, 2019

Leases [Abstract]

Lease, Cost [Table Text Block]



	Three Months Ended		Nine Months Ended
	September 30		September 30
(In thousands)	2019		2019
Operating lease cost	$	18,605	$	54,879
Short-term lease cost	23		56
Variable lease cost	5,335		17,119
Total lease cost	$	23,963	$	72,054

Lessee, Operating Lease, Liability, Maturity [Table Text Block]



	(In thousands)
2019	$	18,464
2020	68,791
2021	58,134
2022	44,780
2023	34,872
Thereafter	51,749
Total undiscounted operating lease payments	276,790
Less: interest	(33,632		)
Total operating lease liabilities	$	243,158

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)	Sep. 30, 2019 customers countries branches
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 (Details)	9 Months Ended
ORGANIZATION Organization (Details)	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Distribution Centers	11

ACCOUNTING POLICIES (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Prepaid expenses and other current assets	$ 80,940			$ 76,980
Assets, Current	2,578,480			2,385,640
Goodwill	1,746,071			1,722,603
Liabilities and Equity	5,047,411			4,605,036
Other Accrued Liabilities, Current	160,062			105,461
Liabilities, Current	1,104,524			1,061,946
Assets	5,047,411			4,605,036
Deferred Tax Liabilities, Net, Noncurrent	147,832			143,967
Liabilities	2,860,701			2,475,310
Retained earnings	2,477,259	$ 2,412,768	$ 2,349,300	2,307,462	$ 2,249,327	$ 2,182,486	$ 2,124,535	$ 2,079,697
Accumulated other comprehensive income	(382,530)	$ (365,674)	$ (385,918)	(408,435)	$ (349,619)	$ (370,105)	$ (341,390)	$ (312,590)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 2,186,710			$ 2,129,726

ACQUISITIONS - ACQUISITIONS (Details) $ in Thousands	9 Months Ended
ACQUISITIONS - ACQUISITIONS (Details) $ in Thousands	Sep. 30, 2019 USD ($) branches	Sep. 30, 2018 USD ($)
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	$ 36,188
Business Acquisition, Effective Date of Acquisition	Mar. 05, 2019
Business Acquisition, Revenue Reported by Acquired Entity for Last Annual Period	$ 100,000
Goodwill, Acquired During Period	$ 5,946
Number of Stores \| branches	500
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	$ 8,446
Payments to Acquire Businesses, Gross	$ 27,742	$ 0

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		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 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	$ 4,948		$ 4,948
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$ 59.71		$ 59.71		$ 59.26
Share-based Compensation Arrangement By Share-based Payment Award, Options and Stock Appreciation Rights, Outstanding [Roll Forward]
Beginning of Year (in shares)	1,749,201		1,749,201
Grants in Period (in shares)	0	9,415	213,618	509,046
Exercises in Period (in shares)			108,022
Forfeitures in Period (in shares)			87,351
Weighted Average Exercise Price, Exercises in Period (in dollars per share)			$ 34.84
Weighted Average Exercise Price, Forfeitures in Period (in dollars per share)			65.96
Weighted Average Exercise Price, Exercisable (in dollars per share)	$ 59.00		$ 59.00
Weighted Average Remaining Contractual Term, Outstanding (in years)			5 years 9 months 18 days
Weighted Average Remaining Contractual Term, Exercisable (in years)			4 years 10 months 24 days
Aggregate Intrinsic Value, Outstanding	$ 4,948		$ 4,948
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number	2,369,878		2,369,878		2,351,633

SCHEDULE OF SHARE-BASED PAYMENT AWARD, VALUATION ASSUMPTIONS (Details) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate		2.80%	2.50%	2.50%
Expected life (in years)		5 years	5 years	5 years
WESCO expected volatility		28.00%	29.00%	28.00%
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	0	9,415	213,618	509,046
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 0	$ 17.40	$ 16.36	$ 18.38
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	6,256	2,686	181,800	119,457
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 47.95	$ 61.41	$ 54.41	$ 62.72
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	0	0	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	$ 0	$ 0	$ 54.64	$ 62.80

SUMMARY OF RESTRICTED STOCK UNITS (Details) - Restricted Stock Units (RSUs) [Member] - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Unvested (in shares)	373,302		373,302		327,798
Granted (in shares)	6,256	2,686	181,800	119,457
Vested (in shares)			(118,560)
Forfeited (in shares)			(17,736)
Unvested, Weighted Average Fair Value (in dollars per share)	$ 60.25		$ 60.25		$ 57.87
Granted, Weighted Average Fair Value (in dollars per share)	$ 47.95	$ 61.41	54.41	$ 62.72
Vested in Period, Weighted Average Fair Value (in dollars per share)			44.58
Forfeited in Period, Weighted Average Fair Value (in dollars per share)			$ 59.57

SUMMARY OF PERFORMANCE-BASED AWARDS (Details) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 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)	195,305		195,305		138,896
Granted (in shares)	0	0	126,874	44,144
Vested (in shares)			(25,696)
Forfeited (in shares)			(44,769)
Unvested, Weighted Average Fair Value (in dollars per share)	$ 60.24		$ 60.24		$ 59.33
Granted, Weighted Average Fair Value (in dollars per share)	$ 0	$ 0	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)			$ 52.15
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)	177,798		177,798
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)	77,856		77,856
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)	80,145		80,145
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)	19,797		19,797

SCHEDULE OF SHARE-BASED PAYMENT AWARD, PERFORMANCE-BASED AWARDS, VALUATION ASSUMPTIONS (Details)	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
WESCO expected volatility	28.00%	29.00%	28.00%
Risk free interest rate	2.80%	2.50%	2.50%

STOCK-BASED COMPENSATION (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended		12 Months Ended
STOCK-BASED COMPENSATION (Details) - USD ($) $ in Millions	Dec. 31, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 4.4	$ 4.1	$ 14.2	$ 12.1
Total unrecognized compensation cost		$ 24.9		$ 24.9
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		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)		177,798		177,798
Scenario, Forecast [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 4.8					$ 0.7	$ 6.7	$ 12.7

SCHEDULE OF EARNINGS PER SHARE, BASIC AND DILUTED (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Abstract]
Net income (loss) attributable to WESCO International, Inc.	$ 64,495	$ 63,464	$ 42,369	$ 66,849	$ 57,940	$ 44,421	$ 170,329	$ 169,210
Weighted average common shares outstanding used in computing basic earnings per share (in shares)	42,100			47,010			43,545	47,044
Common shares issuable upon exercise of dilutive stock options (in shares)	278			476			355	503
Weighted average common shares outstanding and common share equivalents used in computing diluted earnings per share (in shares)	42,378			47,486			43,900	47,547
Earnings Per Share, Basic and Diluted [Abstract]
Basic (in dollars per share)	$ 1.53			$ 1.42			$ 3.91	$ 3.60
Diluted (in dollars per share)	$ 1.52			$ 1.41			$ 3.88	$ 3.56

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

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-Name Accounting Standards Codification
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+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
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+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

EARNINGS PER SHARE (Details) - shares shares in Millions	3 Months Ended	9 Months Ended
EARNINGS PER SHARE (Details) - shares shares in Millions	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 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	1.7	1.8	1.5

EARNINGS PER SHARE Accelerated Share Repurchase (Details) - USD ($) $ in Thousands	3 Months Ended				4 Months Ended	9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Mar. 07, 2019	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Accelerated Share Repurchases [Line Items]
Payments for Repurchase of Common Stock						$ (152,735)	$ (27,055)
Stock Repurchase Program, Authorized Amount								$ 400,000	$ 300,000
Treasury Stock, Shares, Acquired	695,496	2,394,816	365,272	351,821	365,272	3,455,584
Stock Repurchase Program Expiration Date						Dec. 31, 2020
2020 Repurchase Authorization [Member]
Accelerated Share Repurchases [Line Items]
Treasury Stock, Shares, Acquired						3,090,312
Treasury Stock, Common [Member]
Accelerated Share Repurchases [Line Items]
Payments for Repurchase of Common Stock						$ (150,000)

EMPLOYEE BENEFIT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
EMPLOYEE BENEFIT PLANS (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Retirement Benefits [Abstract]
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 100		$ 300
Schedule of Employee Benefit Plans [Line Items]
Defined Benefit Plan, Service Cost	1,158	$ 1,296	3,446	$ 3,955
Postemployment Benefits, Period Expense			24,700	$ 33,500
Deferred Compensation Liability, Classified, Noncurrent	$ 23,800		$ 23,800		$ 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 BENEFIT PLANS Pension Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 100		$ 300
Service cost	1,158	$ 1,296	3,446	$ 3,955
Interest cost	1,098	1,026	3,267	3,131
Expected return on plan assets	(1,433)	(1,482)	(4,265)	(4,522)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(16)	(11)	(47)	(35)
Net periodic benefit cost	807	829	2,401	2,529
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Other Nonoperating Gains (Losses)	$ (400)	$ (500)	$ (1,000)	$ (1,400)

COMMITMENTS AND CONTINGENCIES Guarantees (Details) $ in Millions	9 Months Ended
	Sep. 30, 2019 USD ($)
Guarantees and Product Warranties [Abstract]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 6.8
Guarantor Obligations, Origin and Purpose	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.

INCOME TAXES (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
INCOME TAXES (Details) - USD ($) $ in Millions	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Tax Contingency [Line Items]
Effective tax rate	19.80%	17.20%	21.00%	19.30%
Unrecognized Tax Benefits			$ 1.3
Unrecognized Tax Benefits	$ 0.1		$ 0.1

INCOME TAXES Income Tax Rates (Details)	3 Months Ended		9 Months Ended
INCOME TAXES Income Tax Rates (Details)	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation, Percent	19.80%	17.20%	21.00%	19.30%

OTHER FINANCIAL INFORMATION (Details) - Unsecured Debt [Member] $ in Millions	Sep. 30, 2019 USD ($)
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 SHEETS (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Condensed Financial Information [Line Items]
Cash and cash equivalents	$ 138,160			$ 96,343	$ 142,760			$ 117,953
Trade accounts receivable, net	1,315,026			1,166,607
Inventories, net	961,997			948,726
Prepaid Expense and Other Assets, Current	80,940			76,980
Total current assets	2,578,480			2,385,640
Property, buildings and equipment, net	174,459			160,878
Operating Lease, Right-of-Use Asset	237,252			0
Intangible assets, net	293,493			316,016
Goodwill and other intangibles, net	1,746,071			1,722,603
Other assets	17,656			19,899
Total assets	5,047,411			4,605,036
Accounts payable	849,584			794,348
Short-term debt	25,561			30,785
Total current liabilities	1,104,524			1,061,946
Long-term Debt, Excluding Current Maturities	1,346,333			1,167,311
Operating Lease, Liability, Noncurrent	182,044			0
Total stockholders' equity	2,193,118			2,135,310
Stockholders' Equity Attributable to Noncontrolling Interest	6,408	$ 6,252	$ 6,003	5,584	5,516	$ 5,313	$ 5,046	3,596
Total liabilities and stockholders' equity	5,047,411			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	1,123			1,123
Total current assets	1,123			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	3,383,537			3,182,469
Other assets	0			0
Total assets	3,384,660			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	1,191,542			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	2,193,118			2,135,310
Stockholders' Equity Attributable to Noncontrolling Interest	0			0
Total liabilities and stockholders' equity	3,384,660			3,183,592
Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Cash and cash equivalents	37,889			35,931	57,052			50,602
Trade accounts receivable, net	0			0
Inventories, net	437,470			440,422
Prepaid Expense and Other Assets, Current	27,376			57,586
Total current assets	502,735			533,939
Intercompany receivables, net	0			0
Property, buildings and equipment, net	76,980			63,506
Operating Lease, Right-of-Use Asset	146,247
Intangible assets, net	1,658			2,131
Goodwill and other intangibles, net	257,623			257,623
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	5,318,786			5,137,783
Other assets	854			2,905
Total assets	6,304,883			5,997,887
Accounts payable	418,502			404,373
Short-term debt	0			0
Other Liabilities, Current	69,505			86,600
Total current liabilities	488,007			490,973
Intercompany payables, net	1,352,436			1,355,422
Long-term Debt, Excluding Current Maturities	856,992			842,093
Operating Lease, Liability, Noncurrent	116,336
Liabilities, Other than Long-term Debt, Noncurrent	107,575			126,930
Total stockholders' equity	3,383,537			3,182,469
Stockholders' Equity Attributable to Noncontrolling Interest	0			0
Total liabilities and stockholders' equity	6,304,883			5,997,887
Non-Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Cash and cash equivalents	100,271			60,412	85,708			67,351
Trade accounts receivable, net	1,315,026			1,166,607
Inventories, net	524,527			508,304
Prepaid Expense and Other Assets, Current	136,719			124,523
Total current assets	2,076,543			1,859,846
Intercompany receivables, net	2,543,978			2,403,704
Property, buildings and equipment, net	97,479			97,372
Operating Lease, Right-of-Use Asset	91,005
Intangible assets, net	291,835			313,885
Goodwill and other intangibles, net	1,488,448			1,464,980
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0			0
Other assets	16,802			16,994
Total assets	6,606,090			6,156,781
Accounts payable	431,082			389,975
Short-term debt	25,561			30,785
Other Liabilities, Current	161,795			159,481
Total current liabilities	618,438			580,241
Intercompany payables, net	0			0
Long-term Debt, Excluding Current Maturities	489,341			325,218
Operating Lease, Liability, Noncurrent	65,708
Liabilities, Other than Long-term Debt, Noncurrent	120,225			119,123
Total stockholders' equity	5,318,786			5,137,783
Stockholders' Equity Attributable to Noncontrolling Interest	6,408			5,584
Total liabilities and stockholders' equity	6,606,090			6,156,781
Consolidated Entities [Member]
Condensed Financial Information [Line Items]
Cash and cash equivalents	138,160			96,343	142,760			117,953
Trade accounts receivable, net	1,315,026			1,166,607
Inventories, net	961,997			948,726
Prepaid Expense and Other Assets, Current	163,297			173,964
Total current assets	2,578,480			2,385,640
Intercompany receivables, net	0			0
Property, buildings and equipment, net	174,459			160,878
Operating Lease, Right-of-Use Asset	237,252
Intangible assets, net	293,493			316,016
Goodwill and other intangibles, net	1,746,071			1,722,603
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0			0
Other assets	17,656			19,899
Total assets	5,047,411			4,605,036
Accounts payable	849,584			794,348
Short-term debt	25,561			30,785
Other Liabilities, Current	229,379			236,813
Total current liabilities	1,104,524			1,061,946
Intercompany payables, net	0			0
Long-term Debt, Excluding Current Maturities	1,346,333			1,167,311
Operating Lease, Liability, Noncurrent	182,044
Liabilities, Other than Long-term Debt, Noncurrent	227,800			246,053
Total stockholders' equity	2,193,118			2,135,310
Stockholders' Equity Attributable to Noncontrolling Interest	6,408			5,584
Total liabilities and stockholders' equity	5,047,411			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	(1,921)			(9,268)
Total current assets	(1,921)			(9,268)
Intercompany receivables, net	(2,543,978)			(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	(8,702,323)			(8,320,252)
Other assets	0			0
Total assets	(11,248,222)			(10,733,224)
Accounts payable	0			0
Short-term debt	0			0
Other Liabilities, Current	(1,921)			(9,268)
Total current liabilities	(1,921)			(9,268)
Intercompany payables, net	(2,543,978)			(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	(8,702,323)			(8,320,252)
Stockholders' Equity Attributable to Noncontrolling Interest	0			0
Total liabilities and stockholders' equity	$ (11,248,222)			$ (10,733,224)

CONDENSED CONSOLIDATED INCOME STATEMENTS (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Condensed Financial Information [Line Items]
Revenues	$ 2,148,110			$ 2,067,245			$ 6,259,465	$ 6,165,154
Cost of goods sold	1,747,913			1,670,037			5,067,799	4,988,103
Selling, general and administrative expense	290,852			284,073			883,222	867,790
Depreciation and amortization	15,612			15,618			46,035	47,321
Provision for income taxes	15,886			13,822			44,970	40,077
Net income (loss)	64,339			66,645			169,505	167,289
Less: Net (loss) income attributable to noncontrolling interest	(156)			(204)			(824)	(1,921)
Net income (loss) attributable to WESCO International, Inc.	64,495	$ 63,464	$ 42,369	66,849	$ 57,940	$ 44,421	170,329	169,210
Comprehensive Income:
Foreign currency translation adjustment	(16,856)			20,486			25,905	(37,029)
Comprehensive income attributable to WESCO International, Inc.	47,639			87,335			196,234	132,181
Parent Company [Member]
Condensed Financial Information [Line Items]
Revenues	0			0			0	0
Cost of goods sold	0			0			0	0
Selling, general and administrative expense	0			0			0	0
Depreciation and amortization	0			0			0	0
Income (Loss) from Subsidiaries, before Tax	64,339			66,645			169,505	167,289
Other Nonoperating Income (Expense)	0			0			0	0
Provision for income taxes	0			0			0	0
Net income (loss)	64,339			66,645			169,505	167,289
Less: Net (loss) income attributable to noncontrolling interest	0			0			0	0
Net income (loss) attributable to WESCO International, Inc.	64,339			66,645			169,505	167,289
Comprehensive Income:
Foreign currency translation adjustment	(16,856)			20,486			25,905	(37,029)
Comprehensive income attributable to WESCO International, Inc.	47,483			87,131			195,410	130,260
Non-Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Revenues	1,244,847			1,206,174			3,643,193	3,578,653
Cost of goods sold	1,016,359			981,908			2,966,959	2,915,387
Selling, general and administrative expense	143,927			134,683			437,735	420,353
Depreciation and amortization	10,778			11,143			32,174	33,572
Income (Loss) from Subsidiaries, before Tax	0			0			0	0
Other Nonoperating Income (Expense)	564			3,923			10,078	13,372
Provision for income taxes	14,494			12,746			41,147	37,876
Net income (loss)	58,725			61,771			155,100	158,093
Less: Net (loss) income attributable to noncontrolling interest	(156)			(204)			(824)	(1,921)
Net income (loss) attributable to WESCO International, Inc.	58,881			61,975			155,924	160,014
Comprehensive Income:
Foreign currency translation adjustment	(16,856)			20,486			25,905	(37,029)
Comprehensive income attributable to WESCO International, Inc.	42,025			82,461			181,829	122,985
Consolidated Entities [Member]
Condensed Financial Information [Line Items]
Revenues	2,148,110			2,067,245			6,259,465	6,165,154
Cost of goods sold	1,747,913			1,670,037			5,067,799	4,988,103
Selling, general and administrative expense	290,852			284,073			883,222	867,790
Depreciation and amortization	15,612			15,618			46,035	47,321
Income (Loss) from Subsidiaries, before Tax	0			0			0	0
Other Nonoperating Income (Expense)	(13,508)			(17,050)			(47,934)	(54,574)
Provision for income taxes	15,886			13,822			44,970	40,077
Net income (loss)	64,339			66,645			169,505	167,289
Less: Net (loss) income attributable to noncontrolling interest	(156)			(204)			(824)	(1,921)
Net income (loss) attributable to WESCO International, Inc.	64,495			66,849			170,329	169,210
Comprehensive Income:
Foreign currency translation adjustment	(16,856)			20,486			25,905	(37,029)
Comprehensive income attributable to WESCO International, Inc.	47,639			87,335			196,234	132,181
Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Revenues	939,909			899,994			2,736,224	2,703,468
Cost of goods sold	768,200			727,052			2,220,792	2,189,683
Selling, general and administrative expense	146,925			149,390			445,487	447,437
Depreciation and amortization	4,834			4,475			13,861	13,749
Income (Loss) from Subsidiaries, before Tax	58,725			61,771			155,100	158,093
Other Nonoperating Income (Expense)	(12,944)			(13,127)			(37,856)	(41,202)
Provision for income taxes	1,392			1,076			3,823	2,201
Net income (loss)	64,339			66,645			169,505	167,289
Less: Net (loss) income attributable to noncontrolling interest	0			0			0	0
Net income (loss) attributable to WESCO International, Inc.	64,339			66,645			169,505	167,289
Comprehensive Income:
Foreign currency translation adjustment	(16,856)			20,486			25,905	(37,029)
Comprehensive income attributable to WESCO International, Inc.	47,483			87,131			195,410	130,260
Consolidation, Eliminations [Member]
Condensed Financial Information [Line Items]
Revenues	(36,646)			(38,923)			(119,952)	(116,967)
Cost of goods sold	(36,646)			(38,923)			(119,952)	(116,967)
Selling, general and administrative expense	0			0			0	0
Depreciation and amortization	0			0			0	0
Income (Loss) from Subsidiaries, before Tax	(123,064)			(128,416)			(324,605)	(325,382)
Other Nonoperating Income (Expense)	0			0			0	0
Provision for income taxes	0			0			0	0
Net income (loss)	(123,064)			(128,416)			(324,605)	(325,382)
Less: Net (loss) income attributable to noncontrolling interest	0			0			0	0
Net income (loss) attributable to WESCO International, Inc.	(123,064)			(128,416)			(324,605)	(325,382)
Comprehensive Income:
Foreign currency translation adjustment	33,712			(40,972)			(51,810)	74,058
Comprehensive income attributable to WESCO International, Inc.	(89,352)			(169,388)			(376,415)	(251,324)
Pension Plan [Member]
Condensed Financial Information [Line Items]
Other Nonoperating Gains (Losses)	$ (400)			$ (500)			$ (1,000)	$ (1,400)

CONDENSED CONSOLIDATED STATEMENT OF CASH FLOWS (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	$ 4,575	$ 3,609
Net cash (used) provided by operating activities	116,664	174,460
Payments to Acquire Businesses, Gross	(27,742)	0
Investing Activities:
Capital expenditures	(30,323)	(23,749)
Net cash used in investing activities	(53,490)	(20,140)
Financing Activities:
Payments for Repurchase of Common Stock	(152,735)	(27,055)
Proceeds from (Payments for) Other Financing Activities	175	(8,301)
Net cash used in financing activities	(18,082)	(124,820)
Effect of exchange rate changes on cash and cash equivalents	(3,275)	(4,693)
Net change in cash and cash equivalents	41,817	24,807
Cash and cash equivalents at the beginning of period	96,343	117,953
Cash and cash equivalents at the end of period	138,160	142,760
Parent Company [Member]
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	0	0
Net cash (used) provided by operating activities	9,480	14,198
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	143,255	12,857
Repayments	0	0
SEC Schedule, 12-04, Cash Dividends Paid to Registrant, Subsidiaries and Equity Method Investees	0	0
Payments for Repurchase of Common Stock	(152,735)	27,055
Proceeds from (Payments for) Other Financing Activities	0	0
Net cash used in financing activities	(9,480)	(14,198)
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	(210,320)	(81,128)
Net cash (used) provided by operating activities	210,707	62,439
Payments to Acquire Businesses, Gross	(27,742)
Investing Activities:
Capital expenditures	(13,269)	(12,831)
Proceeds from Dividends Received	67,065	118,271
Net cash used in investing activities	(184,266)	24,312
Financing Activities:
Borrowings	333,418	246,323
Repayments	(344,167)	(318,323)
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	(13,734)	(8,301)
Net cash used in financing activities	(24,483)	(80,301)
Effect of exchange rate changes on cash and cash equivalents	0	0
Net change in cash and cash equivalents	1,958	6,450
Cash and cash equivalents at the beginning of period	35,931	50,602
Cash and cash equivalents at the end of period	37,889	57,052
Non-Guarantor Subsidiaries [Member]
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	4,575	3,609
Net cash (used) provided by operating activities	(103,523)	97,823
Payments to Acquire Businesses, Gross	0
Investing Activities:
Capital expenditures	(17,054)	(10,918)
Proceeds from Dividends Received	0	0
Net cash used in investing activities	(12,479)	(7,309)
Financing Activities:
Borrowings	856,464	933,046
Repayments	(630,263)	(882,239)
SEC Schedule, 12-04, Cash Dividends Paid to Registrant, Subsidiaries and Equity Method Investees	(67,065)	(118,271)
Payments for Repurchase of Common Stock	0	0
Proceeds from (Payments for) Other Financing Activities	0	0
Net cash used in financing activities	159,136	(67,464)
Effect of exchange rate changes on cash and cash equivalents	(3,275)	(4,693)
Net change in cash and cash equivalents	39,859	18,357
Cash and cash equivalents at the beginning of period	60,412	67,351
Cash and cash equivalents at the end of period	100,271	85,708
Consolidated Entities [Member]
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	4,575	3,609
Net cash (used) provided by operating activities	116,664	174,460
Payments to Acquire Businesses, Gross	(27,742)
Investing Activities:
Capital expenditures	(30,323)	(23,749)
Proceeds from Dividends Received	0	0
Net cash used in investing activities	(53,490)	(20,140)
Financing Activities:
Borrowings	1,122,817	1,111,098
Repayments	(974,430)	(1,200,562)
SEC Schedule, 12-04, Cash Dividends Paid to Registrant, Subsidiaries and Equity Method Investees	0	0
Payments for Repurchase of Common Stock	152,735	27,055
Proceeds from (Payments for) Other Financing Activities	(13,734)	(8,301)
Net cash used in financing activities	(18,082)	(124,820)
Effect of exchange rate changes on cash and cash equivalents	(3,275)	(4,693)
Net change in cash and cash equivalents	41,817	24,807
Cash and cash equivalents at the beginning of period	96,343	117,953
Cash and cash equivalents at the end of period	138,160	142,760
Consolidation, Eliminations [Member]
Condensed Financial Information [Line Items]
Payments for (Proceeds from) Other Investing Activities	210,320	81,128
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	(67,065)	(118,271)
Net cash used in investing activities	143,255	(37,143)
Financing Activities:
Borrowings	(210,320)	(81,128)
Repayments	0	0
SEC Schedule, 12-04, Cash Dividends Paid to Registrant, Subsidiaries and Equity Method Investees	(67,065)	(118,271)
Payments for Repurchase of Common Stock	0	0
Proceeds from (Payments for) Other Financing Activities	0	0
Net cash used in financing activities	(143,255)	37,143
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) $ in Millions	9 Months Ended
Subsequent Events (Details) $ in Millions	Sep. 30, 2019 USD ($)
Subsequent Event [Line Items]
Business Acquisition, Effective Date of Acquisition	Mar. 05, 2019
Business Acquisition, Revenue Reported by Acquired Entity for Last Annual Period	$ 100

GOODWILL (Details) - USD ($) $ in Thousands	9 Months Ended
GOODWILL (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Goodwill [Line Items]
Goodwill	$ 1,746,071	$ 1,722,603
Goodwill, Foreign Currency Translation Gain (Loss)	17,522
Goodwill, Acquired During Period	$ 5,946

REVENUE (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
REVENUE (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Deferred Revenue	$ 11,000		$ 11,000		$ 11,800
Revenue from Contract with Customer, Excluding Assessed Tax	2,148,110	$ 2,067,245	6,259,465	$ 6,165,154
Cost of goods sold	1,747,913	1,670,037	5,067,799	4,988,103
Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	755,129	723,869	2,253,974	2,243,590
Construction [Domain]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	714,589	686,165	2,052,061	2,007,708
Utility [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	357,527	345,937	1,012,726	998,438
Commercial, Institutional and Government [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	320,865	311,274	940,704	915,418
UNITED STATES
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,601,962	1,525,393	4,679,251	4,571,533
CANADA
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	431,233	429,830	1,230,855	1,234,600
Non-US [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	114,915	112,022	349,359	359,021
Shipping and Handling [Member]
Disaggregation of Revenue [Line Items]
Cost of goods sold	$ 17,600	$ 18,800	$ 52,800	$ 55,600

REVENUE Deferred Revenue (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Deferred Revenue	$ 11.0	$ 11.8

REVENUE Shipping and Handling Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Cost of goods sold	$ 1,747,913	$ 1,670,037	$ 5,067,799	$ 4,988,103
Shipping and Handling [Member]
Cost of goods sold	$ 17,600	$ 18,800	$ 52,800	$ 55,600

REVENUE Variable Consideration (Details)	9 Months Ended
REVENUE Variable Consideration (Details)	Sep. 30, 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 September 30, 2019 and 2018 by approximately $26.3 million and $25.1 million, respectively, and by approximately $80.1 million and $74.5 million for the nine months ended September 30, 2019 and 2018, respectively.

LEASES (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
LEASES (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
Leases [Abstract]
Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months	$ 18,464	$ 18,464
Operating Leases, Future Minimum Payments Due, Next Twelve Months			$ 71,640
Operating Lease, Weighted Average Remaining Lease Term	5 years 4 months 24 days	5 years 4 months 24 days
Operating Lease, Right-of-Use Asset	$ 237,252	$ 237,252	0
Operating Lease, Cost	18,605	54,879
Operating Lease, Payments		48,484
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability		48,622
Short-term Lease, Cost	23	56
Variable Lease, Cost	5,335	17,119
Lease, Cost	23,963	72,054
Operating Lease, Liability, Current	61,114	61,114
Operating Lease, Liability, Noncurrent	182,044	182,044	0
Operating Lease, Liability	$ 243,158	$ 243,158
Operating Lease, Weighted Average Discount Rate, Percent	4.60%	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	$ 68,791	$ 68,791
Lessee, Operating Lease, Liability, Payments, Due Year Three	58,134	58,134
Lessee, Operating Lease, Liability, Payments, Due Year Four	44,780	44,780
Lessee, Operating Lease, Liability, Payments, Due Year Five	34,872	34,872
Lessee, Operating Lease, Liability, Payments, Due after Year Five	51,749	51,749
Lessee, Operating Lease, Liability, Payments, Due	276,790	276,790
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	$ (33,632)	$ (33,632)