WESCO International (WCC) 10-Q 9 Nov 20 2020 Q3 Quarterly report Financial data

COVER PAGE

COVER PAGE - shares	9 Months Ended
	Sep. 30, 2020	Nov. 06, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2020
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
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		50,042,827
Entity Registrant Name	WESCO International, Inc.
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Central Index Key	0000929008
Entity Listings [Line Items]
Security Exchange Name	NYSE
Document Period End Date	Sep. 30, 2020
Series A Preferred Stock [Member]
Cover [Abstract]
Title of 12(b) Security	Depositary Shares, each representing a 1/1,00th interest in a share of Series A Fixed-Rate Reset Cumulative Perpetual Preferred Stock
Trading Symbol	WCC PR A
Security Exchange Name	NYSE
Entity Listings [Line Items]
Title of 12(b) Security	Depositary Shares, each representing a 1/1,00th interest in a share of Series A Fixed-Rate Reset Cumulative Perpetual Preferred Stock
Trading Symbol	WCC PR A
Security Exchange Name	NYSE
Preferred Share Purchase Right [Member]
Cover [Abstract]
Title of 12(b) Security	Preferred Share Purchase Rights
Trading Symbol	N/A
Security Exchange Name	NYSE
Entity Listings [Line Items]
Title of 12(b) Security	Preferred Share Purchase Rights
Trading Symbol	N/A
Security Exchange Name	NYSE
Common Class A [Member]
Cover [Abstract]
Title of 12(b) Security	Common Stock, par value $.01 per share
Trading Symbol	WCC
Entity Listings [Line Items]
Title of 12(b) Security	Common Stock, par value $.01 per share
Trading Symbol	WCC

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current Assets:
Cash and cash equivalents	$ 352,249	$ 150,902
Accounts Receivable, after Allowance for Credit Loss, Current	2,492,248	1,187,359
Accounts and Other Receivables, Net, Current	229,275	98,029
Inventories, net	2,357,634	1,011,674
Prepaid expenses and other current assets	166,044	92,447
Total current assets	5,597,450	2,540,411
Property, buildings and equipment, net of accumulated depreciation of $229,041 and $213,758 in 2014 and 2013, respectively	400,222	181,448
Operating Lease, Right-of-Use Asset	540,142	235,834
Intangible assets, net	2,078,468	287,275
Goodwill	3,118,818	1,759,040
Other assets	133,239	13,627
Total assets	11,868,339	5,017,635
Current Liabilities:
Accounts payable	1,830,877	830,478
Accrued payroll and benefit costs	146,670	49,508
Current portion of long-term debt	28,844	26,685
Other Accrued Liabilities, Current	534,544	177,388
Total current liabilities	2,540,935	1,084,059
Total long-term debt	4,878,124	1,257,067
Operating Lease, Liability, Noncurrent	419,718	179,830
Other noncurrent liabilities	292,380	91,391
Deferred Income Tax Liabilities, Net	523,958	146,617
Total liabilities	8,655,115	2,758,964
Commitments and Contingencies
Stockholders' Equity:
Additional capital	1,939,101	1,039,347
Retained earnings	2,596,022	2,530,429
Treasury stock, at cost; 21,859,301 and 21,850,356 shares in 2020 and 2019, respectively	(937,520)	(937,157)
Accumulated other comprehensive income	(377,461)	(367,772)
Total WESCO International, Inc. stockholders' equity	3,220,861	2,265,483
Noncontrolling interest	(7,637)	(6,812)
Total stockholders’ equity	3,213,224	2,258,671
Accounts Receivable, Allowance for Credit Loss, Current	26,220	25,443
Accumulated depreciation	294,638	268,415
Finite-Lived Intangible Assets, Accumulated Amortization	323,887	280,442
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	92,343	8,876
Total liabilities and stockholders' equity	$ 11,868,339	$ 5,017,635
Treasury stock, shares (in shares)	21,859,301	21,850,356
Common Stock [Member]
Stockholders' Equity:
Common stock	$ 676	$ 593
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)	67,562,621	59,308,018
Common stock, shares outstanding (in shares)	50,042,751	41,797,093
Common Class B [Member]
Stockholders' Equity:
Common stock	$ 43	$ 43
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
Series A Preferred Stock [Member]
Stockholders' Equity:
Preferred stock, $.01 par value; 20,000,000 shares authorized, no shares issued or outstanding	$ 0	$ 0
Preferred stock, par value (in dollars per share)	$ 0.01
Preferred stock, shares authorized (in shares)	25,000
Preferred stock, shares issued (in shares)	21,612	0
Preferred stock, shares outstanding (in shares)	21,612
Preferred Stock
Stockholders' Equity:
Preferred stock, $.01 par value; 20,000,000 shares authorized, no shares issued or outstanding	$ 0	$ 0
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

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parentheticals) - USD ($) $ in Thousands	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Allowance for doubtful accounts	$ 26,220			$ 25,443
Accumulated depreciation	294,638			268,415
Finite-Lived Intangible Assets, Accumulated Amortization	323,887			280,442
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ 92,343			$ 8,876
Treasury stock, shares (in shares)	21,859,301	21,859,194	21,848,336	21,850,356	21,849,933	21,154,343	18,756,498	18,391,042
Common Stock [Member]
Common stock, par value (in dollars per share)	$ 0.01			$ 0.01
Common stock, shares authorized (in shares)	210,000,000			210,000,000
Common stock, shares, issued (in shares)	67,562,621	67,562,199	59,381,958	59,308,018	59,294,497	59,292,704	59,271,892	59,157,696
Common stock, shares outstanding (in shares)	50,042,751			41,797,093
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	4,339,431	4,339,431	4,339,431	4,339,431	4,339,431	4,339,431
Common stock, shares outstanding (in shares)	0			0

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Gross Profit [Abstract]
Revenues	$ 4,141,801	$ 2,148,110	$ 8,197,154	$ 6,259,465
Cost of goods sold	3,356,259	1,747,913	6,641,438	5,067,799
Operating Expenses [Abstract]
Selling, general and administrative expense	561,971	290,852	1,221,114	883,222
Depreciation and amortization	45,476	15,612	80,324	46,035
Income from operations	178,095	93,733	254,278	262,409
Nonoperating Income (Expense)	74,540	14,306	152,281	49,293
Other Nonoperating Income (Expense)	(777)	(798)	(1,463)	(1,359)
Income before income taxes	104,332	80,225	103,460	214,475
Provision for income taxes	24,294	15,886	23,707	44,970
Net income	80,038	64,339	79,753	169,505
Net (loss) income attributable to noncontrolling interest	(640)	(156)	(825)	(824)
Net income attributable to WESCO International, Inc.	80,678	64,495	80,578	170,329
Comprehensive Income:
Foreign currency translation adjustment	41,428	(16,856)	(9,689)	25,905
Comprehensive income attributable to WESCO International, Inc.	$ 107,595	$ 47,639	$ 55,102	$ 196,234
Earnings per share attributable to WESCO International, Inc.
Basic (in dollars per share)	$ 1.32	$ 1.53	$ 1.44	$ 3.91
Diluted (in dollars per share)	$ 1.31	$ 1.52	$ 1.44	$ 3.88
Preferred Stock Dividends, Income Statement Impact	$ 14,511	$ 0	$ 15,787	$ 0
Net Income (Loss) Available to Common Stockholders, Basic	66,167	64,495	64,791	170,329
Shipping and Handling [Member]
Gross Profit [Abstract]
Cost of goods sold	$ 55,500	$ 17,600	$ 94,400	$ 52,800

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Operating Activities:
Net income	$ 79,753	$ 169,505
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	80,324	46,035
Deferred income taxes	(8,261)	4,621
Other operating activities, net	(1,763)	10,876
Changes in assets and liabilities
Increase (Decrease) in Accounts Receivable	(3,584)	122,903
Increase (Decrease) in Accounts and Other Receivables	14,702	(15,450)
Inventories, net	77,681	(1,500)
Prepaid expenses and other current assets	(26,655)	(20,720)
Accounts payable	80,489	46,902
Accrued payroll and benefit costs	25,872	(36,055)
Other current and noncurrent liabilities	122,616	4,453
Net cash provided by operating activities	418,938	116,664
Investing Activities:
Capital expenditures	(42,562)	(30,323)
Payments to Acquire Businesses, Gross	(3,707,575)	(27,742)
Other investing activities	26,240	4,575
Net cash used in investing activities	(3,723,897)	(53,490)
Financing Activities:
Proceeds from (Repayments of) Short-term Debt	(9,824)	(29,600)
Proceeds from issuance of long-term debt	4,661,830	1,105,397
Repayments of Long-term Debt	(1,045,667)	(927,410)
Payments for Repurchase of Common Stock	(2,032)	(152,735)
Payments of Debt Issuance Costs	(79,945)	(2,508)
Payments of Dividends	(15,787)	0
Other financing activities, net	(1,255)	(11,226)
Net cash used in financing activities	3,507,320	(18,082)
Effect of exchange rate on cash and cash equivalents	(1,014)	(3,275)
Cash and cash equivalents at the beginning of period	150,902	96,343
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect, Total	201,347	41,817
Cash and cash equivalents at the end of period	352,249	138,160
Interest Paid, Including Capitalized Interest, Operating and Investing Activities	36,035	38,347
Income Taxes Paid	44,994	54,044
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	$ 80,626	$ 48,622

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY Statement - USD ($) $ in Thousands	Total	Common Class B [Member]	Common Stock [Member]	Series A Preferred Stock [Member]	Series A	AOCI Attributable to Parent [Member]	Noncontrolling Interest [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Additional Paid-in Capital [Member]
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)
Preferred stock, $.01 par value; 20,000,000 shares authorized, no shares issued or outstanding				$ 0
Preferred stock, shares issued (in shares)				0
Stock Issued, Value, Stock Options Exercised, Net of Tax Benefit (Expense)			$ 1					$ (54)
APIC, Share-based Payment Arrangement, Recognition and Exercise	(90)
Shares Granted, Value, Share-based Payment Arrangement, after Forfeiture	4,665
ERROR in label resolution.										$ 19,144
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation			$ 0						$ (531)	(1,822)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period			(156,760)					(184)
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation			(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)
Preferred stock, $.01 par value; 20,000,000 shares authorized, no shares issued or outstanding				$ 0
Preferred stock, shares issued (in shares)				0
Stock Issued, Value, Stock Options Exercised, Net of Tax Benefit (Expense)			$ 0					$ (157)
APIC, Share-based Payment Arrangement, Recognition and Exercise	6
Shares Granted, Value, Share-based Payment Arrangement, after Forfeiture	5,150
ERROR in label resolution.										(22,500)
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation			$ 0						4	(1)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period			(20,831)					(3,029)
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation			(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)
Preferred stock, $.01 par value; 20,000,000 shares authorized, no shares issued or outstanding				$ 0
Preferred stock, shares issued (in shares)				0
Stock Issued, Value, Stock Options Exercised, Net of Tax Benefit (Expense)			$ 0					$ (5)
APIC, Share-based Payment Arrangement, Recognition and Exercise	0
Shares Granted, Value, Share-based Payment Arrangement, after Forfeiture	4,426
ERROR in label resolution.										32,257
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation			$ 0						(4)	(13)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period			(1,983)					(94)
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation			(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)
Preferred stock, $.01 par value; 20,000,000 shares authorized, no shares issued or outstanding				$ 0
Preferred stock, shares issued (in shares)				0
Common Stock, Value, Issued		$ 43	$ 593
Common Stock, Shares, Issued		4,339,431	59,308,018
Additional capital	1,039,347
Retained Earnings (Accumulated Deficit)	2,530,429
Treasury Stock, Value	$ (937,157)
ERROR in label resolution.	(21,850,356)
Stockholders' Equity Attributable to Noncontrolling Interest	$ (6,812)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(367,772)
Preferred stock, $.01 par value; 20,000,000 shares authorized, no shares issued or outstanding				$ 0
Preferred stock, shares issued (in shares)				0
Stock Issued, Value, Stock Options Exercised, Net of Tax Benefit (Expense)			$ 1					$ 79
APIC, Share-based Payment Arrangement, Recognition and Exercise	(39)
Shares Granted, Value, Share-based Payment Arrangement, after Forfeiture	4,626
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation			$ 0						761	(2,297)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period			(105,620)					2,020
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation			(31,680)
Net Income (Loss) Attributable to Parent	34,407
Net Income (Loss) Attributable to Noncontrolling Interest							(232)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax						(93,851)
Net Income (Loss) Attributable to Parent	80,578
Net Income (Loss) Attributable to Noncontrolling Interest	(825)
Common Stock, Value, Issued		$ 43	$ 594
Common Stock, Shares, Issued		4,339,431	59,381,958
Additional capital	1,041,637
Retained Earnings (Accumulated Deficit)	2,565,597
Treasury Stock, Value	$ (937,078)
ERROR in label resolution.	(21,848,336)
Stockholders' Equity Attributable to Noncontrolling Interest	$ (7,044)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(461,623)
Preferred stock, $.01 par value; 20,000,000 shares authorized, no shares issued or outstanding				$ 0
Preferred stock, shares issued (in shares)				0
Stock Issued, Value, Stock Options Exercised, Net of Tax Benefit (Expense)			$ 0					$ (437)
APIC, Share-based Payment Arrangement, Recognition and Exercise	0
Shares Granted, Value, Share-based Payment Arrangement, after Forfeiture	4,901
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation			$ 0						27	(37)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period			(30,665)					(10,858)
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation			(652)
Net Income (Loss) Attributable to Parent	(34,506)
Dividends, Preferred Stock				$ (1,276)
Net Income (Loss) Attributable to Noncontrolling Interest							47
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax						42,734
Stock Issued During Period, Value, Purchase of Assets			$ 82		$ 0					886,740
Stock Issued During Period, Shares, Purchase of Assets			8,150,228	21,612
Common Stock, Value, Issued		$ 43	$ 676
Common Stock, Shares, Issued		4,339,431	67,562,199
Additional capital	1,933,241
Retained Earnings (Accumulated Deficit)	2,529,842
Treasury Stock, Value	$ (937,515)
ERROR in label resolution.	(21,859,194)
Stockholders' Equity Attributable to Noncontrolling Interest	$ (6,997)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(418,889)
Preferred stock, $.01 par value; 20,000,000 shares authorized, no shares issued or outstanding				$ 0
Preferred stock, shares issued (in shares)				21,612
Stock Issued, Value, Stock Options Exercised, Net of Tax Benefit (Expense)			$ 0					$ (5)
APIC, Share-based Payment Arrangement, Recognition and Exercise	0
Shares Granted, Value, Share-based Payment Arrangement, after Forfeiture	6,002
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation			$ 0						$ 13	(3)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period			(479)					(107)
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation			(57)
Net Income (Loss) Attributable to Parent	80,678
Dividends, Preferred Stock				$ (14,511)
Net Income (Loss) Attributable to Noncontrolling Interest	(640)						$ (640)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax						$ 41,428
Stock Issued During Period, Value, Purchase of Assets										$ (139)
Common Stock, Value, Issued		$ 43	$ 676
Common Stock, Shares, Issued		4,339,431	67,562,621
Additional capital	1,939,101
Retained Earnings (Accumulated Deficit)	2,596,022
Treasury Stock, Value	$ (937,520)
ERROR in label resolution.	(21,859,301)
Stockholders' Equity Attributable to Noncontrolling Interest	$ (7,637)
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (377,461)
Preferred stock, $.01 par value; 20,000,000 shares authorized, no shares issued or outstanding				$ 0
Preferred stock, shares issued (in shares)				21,612

ORGANIZATION

ORGANIZATION	9 Months Ended
	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
ORGANIZATION	WESCO International, Inc. ("WESCO International") and its subsidiaries (collectively, “WESCO” or the "Company"), headquartered in Pittsburgh, Pennsylvania, is a leading provider of business-to-business distribution, logistics services and supply chain solutions. On June 22, 2020, WESCO completed its previously announced acquisition of Anixter International Inc., a Delaware corporation (“Anixter”). Pursuant to the terms of the Agreement and Plan of Merger, dated January 10, 2020 (the “Merger Agreement”), by and among Anixter, WESCO and Warrior Merger Sub, Inc., a Delaware corporation and a wholly owned subsidiary of WESCO (“Merger Sub”), Merger Sub was merged with and into Anixter (the “Merger”), with Anixter surviving the Merger and continuing as a wholly owned subsidiary of WESCO.

ACCOUNTING POLICIES

ACCOUNTING POLICIES	9 Months Ended
	Sep. 30, 2020
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 2019 Annual Report on Form 10-K as filed with the SEC on February 24, 2020. The Condensed Consolidated Balance Sheet at December 31, 2019 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, 2020, the unaudited Condensed Consolidated Statements of Income and Comprehensive Income, the unaudited Condensed Consolidated Statements of Stockholders' Equity for the three and nine months ended September 30, 2020 and 2019, and the unaudited Condensed Consolidated Statements of Cash Flows for the nine months ended September 30, 2020 and 2019, 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. In the third quarter of 2020, in connection with the acquisition of Anixter, the Company identified new operating segments. These operating segments, which have been organized around three strategic business units, consist of Electrical & Electronic Solutions ("EES"), Communications & Security Solutions ("CSS") and Utility & Broadband Solutions ("UBS"). The Company's operating segments, which are equivalent to its reportable segments, are described further in Note 14. The applicable comparative financial information reported in the Company's previously issued interim financial statements for the three and nine months ended September 30, 2019 has been recast in this Quarterly Report on Form 10-Q to conform to the basis of the new segments. Reclassifications The Condensed Consolidated Balance Sheet as of December 31, 2019, the unaudited Condensed Consolidated Statements of Income and Comprehensive Income for the three and nine months ended September 30, 2019, and the unaudited Condensed Consolidated Statement of Cash Flows for the nine months ended September 30, 2019, respectively, include certain reclassifications to previously reported amounts to conform to the current period presentation. Recently Adopted Accounting Pronouncements In June 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , which introduced new guidance for the accounting for credit losses on certain financial instruments. The Company adopted this ASU effective January 1, 2020. The adoption of this new credit loss guidance did not have a material impact on the unaudited condensed consolidated financial statements and notes thereto presented herein, and WESCO does not expect it to have a material impact on its financial position or results of operation on an ongoing basis. 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 Company adopted this ASU in the first quarter of 2020. The adoption of this guidance did not have a material impact on the unaudited condensed consolidated financial statements and notes thereto presented herein. In August 2018, the FASB issued ASU 2018-15, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract , which aligned the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The standard was effective for fiscal years beginning after December 15, 2019. The Company adopted this ASU in the first quarter of 2020. The adoption of this guidance did not have a material impact on the unaudited condensed consolidated financial statements and notes thereto presented herein. Recently Issued Accounting Pronouncements 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 condensed consolidated financial statements and notes thereto. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes , which removes certain exceptions to the general principles of Accounting Standards Codification Topic 740, Income Taxes , and simplifies other aspects of accounting for income taxes. The amendments in this ASU are effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020. Early adoption is permitted in any interim or annual period, with any adjustments reflected as of the beginning of the fiscal year of adoption. Management does not expect the adoption of this accounting standard to have a material impact on its condensed consolidated financial statements and notes thereto. In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting , which provides optional guidance for a limited period of time to ease the potential burden in accounting for (or recognizing the effects of) reference rate reform on financial reporting. The amendments in this Update are effective for all entities as of March 12, 2020 through December 31, 2022. Management is currently evaluating the impact related to the replacement of London Interbank Offered Rate (LIBOR) and whether the Company will elect the adoption of the optional guidance. 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.

REVENUE (Notes)

REVENUE (Notes)	9 Months Ended
	Sep. 30, 2020
Revenue from Contract with Customer [Abstract]
Revenue from Contract with Customer	3. REVENUE WESCO distributes products and provides services to customers globally in various end markets within its business segments. The segments, which consist of Electrical & Electronic Solutions, Communications & Security Solutions, and Utility & Broadband Solutions operate in the United States, Canada and various other foreign countries. 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 net sales by segment and geography for the periods presented: Three Months Ended Nine Months Ended September 30 September 30 (In thousands) 2020 2019 2020 2019 Electrical & Electronic Solutions $ 1,653,726 $ 1,250,080 $ 3,811,498 $ 3,626,423 Communications & Security Solutions 1,388,791 235,920 1,953,967 681,087 Utility & Broadband Solutions 1,099,284 662,110 2,431,689 1,951,955 Total by segment $ 4,141,801 $ 2,148,110 $ 8,197,154 $ 6,259,465 Three Months Ended Nine Months Ended September 30 September 30 (In thousands) 2020 2019 2020 2019 United States $ 3,033,101 $ 1,601,962 $ 6,100,877 $ 4,679,251 Canada 582,700 431,233 1,311,724 1,230,855 Other International 526,000 114,915 784,553 349,359 Total by geography (1) $ 4,141,801 $ 2,148,110 $ 8,197,154 $ 6,259,465 (1) WESCO attributes revenues from external customers to individual countries on the basis of point of sale. 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, 2020 and December 31, 2019, $27.7 million and $12.3 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, 2020 and 2019 by approximately $75.4 million and $26.3 million, respectively, and by approximately $129.0 million and $80.1 million for the nine months ended September 30, 2020 and 2019, respectively. Shipping and handling activities are recognized in net sales when they are billed to the customer. The related costs are recognized as a component of selling, general and administrative expenses. 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 $55.5 million and $17.6 million for the three months ended September 30, 2020 and 2019, respectively, and $94.4 million and $52.8 million for the nine months ended September 30, 2020 and 2019, respectively.

ACQUISITIONS

ACQUISITIONS	9 Months Ended
	Sep. 30, 2020
Business Combinations [Abstract]
Business Combination Disclosure	4. ACQUISITIONS Anixter International Inc. As described in Note 1, on June 22, 2020, WESCO completed its previously announced merger with Anixter. The Company used the net proceeds from the issuance of senior unsecured notes, borrowings under its revolving credit facility and accounts receivable securitization facility (as described further in Note 8), as well as cash on hand, to finance the acquisition of Anixter and related transaction costs. At the effective time of the Merger, each outstanding share of common stock of Anixter (subject to limited exceptions) was converted into the right to receive (i) $72.82 in cash, (ii) 0.2397 shares of common stock of WESCO, par value $0.01 per share (the “WESCO Common Stock”) and (iii) 0.6356 depositary shares, each representing a 1/1,000th interest in a share of newly issued fixed-rate reset cumulative perpetual preferred stock of WESCO, Series A, with a $25,000 stated amount per whole preferred share and an initial dividend rate equal to 10.625%. Anixter is a leading distributor of network and security solutions, electrical and electronic solutions, and utility power solutions with locations in over 300 cities across approximately 50 countries, and 2019 annual sales of more than $8 billion. The Merger brought together two companies with highly compatible capabilities and characteristics. The combination of WESCO and Anixter created an enterprise with scale and should afford the Company the opportunity to digitize its business, and expand its services portfolio and supply chain offerings. The total preliminary estimated fair value of consideration transferred for the Merger consisted of the following: (In thousands) Cash portion attributable to common stock outstanding $ 2,476,010 Cash portion attributable to options and restricted stock units outstanding 87,375 Fair value of cash consideration 2,563,385 Common stock consideration 313,512 Series A preferred stock consideration 573,786 Fair value of equity consideration 887,298 Extinguishment of Anixter obligations, including accrued and unpaid interest 1,247,653 Total purchase consideration $ 4,698,336 Supplemental cash flow disclosure related to acquisitions: Cash paid for acquisition $ 3,811,038 Less: Cash acquired (103,463) Cash paid for acquisition, net of cash acquired $ 3,707,575 The Merger was accounted for as a business combination with WESCO acquiring Anixter in accordance with Accounting Standards Codification (“ASC”) 805, Business Combinations . Under the acquisition method of accounting, the preliminary purchase consideration was allocated to the identified assets acquired and liabilities assumed based on their respective acquisition date fair value, with any excess allocated to goodwill. The fair value estimates were based on income, market and cost valuation methods using primarily unobservable inputs developed by management, which are categorized within Level 3 of the fair value hierarchy. Significant inputs used to value the identifiable intangible assets included projected revenues, estimated future cash flows, discount rates, royalty rates, and applicable income tax rates. The excess purchase consideration recorded to goodwill is not deductible for income tax purposes, and has been assigned to the Company's reportable segments based on their relative fair values, as disclosed in Note 5. The resulting goodwill is primarily attributable to Anixter's workforce, significant cross-selling opportunities in additional geographies, enhanced scale, and other operational efficiencies. In the third quarter of 2020, the Company recognized adjustments to total identifiable intangible assets and deferred income taxes of $5.4 million and $7.3 million, respectively. Certain other measurement period adjustments were made to the identified assets acquired and liabilities assumed, none of which were significant, individually or in aggregate. The net impact of the adjustments made in the third quarter of 2020 was a decrease to goodwill of $7.6 million. The estimated fair values of assets acquired and liabilities assumed are based on preliminary calculations and valuations using estimates and assumptions at the time of acquisition. The determination of the fair values of assets acquired and liabilities assumed, especially those related to identifiable intangible assets, is preliminary due to the complexity of combining multibillion dollar businesses. Accordingly, as the Company obtains additional information during the measurement period (not to exceed one year from the acquisition date), estimates and assumptions for the preliminary purchase consideration allocations may change materially. The following table sets forth the preliminary allocation of the purchase consideration to the respective fair value of assets acquired and liabilities assumed for the acquisition of Anixter: (In thousands) Assets Cash and cash equivalents $ 103,463 Trade accounts receivable 1,309,104 Other accounts receivable 116,386 Inventories 1,424,678 Prepaid expenses and other current assets 53,462 Property, buildings and equipment 213,020 Operating lease assets 262,413 Intangible assets 1,838,065 Goodwill 1,360,373 Other assets 112,386 Total assets $ 6,793,350 Liabilities Accounts payable $ 920,163 Accrued payroll and benefit costs 69,480 Short-term debt and current portion of long-term debt 13,225 Other current liabilities 222,615 Long-term debt 77,822 Operating lease liabilities 199,959 Deferred income taxes 384,890 Other noncurrent liabilities 206,860 Total liabilities $ 2,095,014 Fair value of net assets acquired, including goodwill and intangible assets $ 4,698,336 The following table sets forth the preliminary identifiable intangible assets and their estimated weighted-average useful lives: Identifiable Intangible Assets Estimated Weighted-Average Estimated Useful Life in Years (In thousands) Customer relationships $ 1,098,900 16 Trademarks 735,000 Indefinite Non-compete agreements 4,165 1 Total identifiable intangible assets $ 1,838,065 The results of operations of Anixter are included in the unaudited condensed consolidated financial statements beginning on June 22, 2020, the acquisition date. For the three and nine months ended September 30, 2020, the condensed consolidated statements of income include $2.2 billion and $2.4 billion of net sales, respectively, and $80.0 million and $98.4 million of income from operations for Anixter, respectively. Transaction costs related to the merger were comprised of legal, advisory and other costs of $14.5 million and $92.1 million, which are included in selling, general and administrative expenses for the three and nine months ended September 30, 2020, respectively. Pro Forma Financial Information The following unaudited pro forma financial information presents combined results of operations for the periods presented, as if the Company had completed the Merger on January 1, 2019. The unaudited pro forma financial information includes adjustments to amortization and depreciation for intangible assets and property, buildings and equipment, adjustments to interest expense for the additional indebtedness incurred to complete the acquisition (including the amortization of debt discount and issuance costs), transaction costs, change in control and severance costs, dividends accrued on the Series A preferred stock, compensation expense associated with the WESCO phantom stock unit awards described in Note 10, as well as the respective income tax effects of such adjustments. For the three months ended September 30, 2020 and 2019, adjustments totaling $1.5 million and $57.4 million, respectively, decreased the unaudited pro forma net income attributable to common stockholders. For the nine months ended September 30, 2020 and 2019, adjustments totaling $0.4 million and $167.8 million, respectively, decreased the unaudited pro forma net income attributable to common stockholders. The unaudited pro forma financial information does not reflect any cost savings, operating synergies or revenue enhancements that WESCO may achieve as a result of its acquisition of Anixter, the costs to integrate the operations of WESCO and Anixter or the costs necessary to achieve these cost savings, operating synergies and revenue enhancements. The unaudited pro forma financial information presented below is not necessarily indicative of consolidated results of operations of the combined business had the acquisition occurred at the beginning of the respective fiscal years, nor is it necessarily indicative of future results of operations of the combined company. Three Months Ended Nine Months Ended (In thousands) September 30, September 30, September 30, September 30, Pro forma net sales $ 4,111,716 $ 4,332,980 $ 11,802,538 $ 12,758,461 Pro forma net income attributable to common stockholders 63,844 66,416 106,858 164,424 On August 6, 2020, the Company entered into a Consent Agreement with the Competition Bureau of Canada regarding the merger with Anixter. Under the Consent Agreement, the Company is required to divest its legacy Utility and Datacom businesses in Canada, which had total sales of less than $150 million in 2019. The process to divest the businesses has commenced, and WESCO is working to complete the divestitures on a timely basis. The Company expects to use the net proceeds from the divestiture to repay indebtedness. 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"). 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 then outstanding 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 $11.6 million, which is deductible for tax purposes. The following table sets forth the consideration paid for the acquisition of SLS: Nine Months Ended September 30 2019 (In thousands) Fair value of assets acquired $ 34,812 Fair value of liabilities assumed 7,070 Cash paid for acquisition $ 27,742

GOODWILL (Notes)

GOODWILL (Notes)	9 Months Ended
	Sep. 30, 2020
Goodwill [Line Items]
Goodwill and Intangible Assets Disclosure	5. GOODWILL AND INTANGIBLE ASSETS The following table sets forth the changes in the carrying value of goodwill: Nine Months Ended September 30 2020 EES CSS UBS Total (In thousands) Beginning balance January 1 $ 573,447 $ 235,711 $ 949,882 $ 1,759,040 Adjustments to goodwill for acquisitions (Note 4) (1) (2) 245,624 858,022 262,544 1,366,190 Foreign currency exchange rate changes (9,137) 323 2,402 (6,412) Ending balance September 30 $ 809,934 $ 1,094,056 $ 1,214,828 $ 3,118,818 (1) Adjustments to goodwill include the final allocation of the purchase price paid for SLS, as described in Note 4, to the respective assets acquired and liabilities assumed. (2) The effect of the merger with Anixter on the Company's determination of reportable segments is disclosed in Note 14. Certain triggering events occurred during the first quarter of 2020, including the effect of the ongoing macroeconomic disruption and uncertainty caused by the COVID-19 pandemic, as well as the decline in the Company's share price and market capitalization, both of which indicated that the carrying value of goodwill and indefinite-lived intangible assets may not be recoverable. Accordingly, the Company performed an interim test for impairment as of March 31, 2020. There were no impairment losses identified as a result of this interim test. As disclosed in Note 1, the Company identified new operating segments during the third quarter of 2020, which changed the composition of its reporting units. Accordingly, the Company reassigned goodwill to the new reporting units using a relative fair value allocation approach. The Company performed a goodwill impairment test immediately before and after it reorganized its reporting structure. Goodwill was tested for impairment on a reporting unit level and the evaluation involved comparing the fair value of each reporting unit to its carrying value. The fair values of the Company's reporting units were determined using a combination of a discounted cash flow analysis and market multiples. In performing the quantitative assessments, management used expected operating margins supported by a combination of historical results, current forecasts, market data and recent economic events, which are categorized within Level 3 of the fair value hierarchy. The Company used a discount rate that reflects market participants' cost of capital. There were no impairment losses identified as a result of these tests. Although all of the Company's reporting units have fair values that currently exceed the respective carrying values, the EES reporting unit with goodwill of $809.9 million had an estimated fair value that exceeded its respective carrying value by less than 10%. The determination of fair value of the reporting units involves significant management judgment, particularly as it relates to the underlying assumptions and factors around expected operating margins and discount rate. Due to the ongoing uncertainty surrounding the current macroeconomic environment and conditions in the markets in which WESCO operates, as well as the risk that the Company may not fully realize cost savings, operating synergies or revenue improvement as a result of its acquisition of Anixter, there can be no assurance that the fair values of the Company's reporting units will exceed their carrying values in the future, and that goodwill and indefinite-lived intangible assets will be fully recoverable. The components of intangible assets are as follows: September 30, 2020 December 31, 2019 (In thousands) Gross Carrying Amount (1) Accumulated Amortization (1) Net Carrying Amount Gross Carrying Amount (1) Accumulated Amortization (1) Net Carrying Amount Intangible assets: Life Trademarks Indefinite $ 832,525 $ — $ 832,525 $ 98,699 $ — $ 98,699 Trademarks 10 - 15 24,894 (10,961) 13,933 24,800 (9,319) 15,481 Non-compete agreements 2 - 5 4,342 (694) 3,648 196 (180) 16 Customer relationships 10 - 20 1,455,003 (237,896) 1,217,107 358,341 (201,962) 156,379 Distribution agreements 10 - 19 37,281 (27,031) 10,250 37,371 (25,294) 12,077 Patents 10 48,310 (47,305) 1,005 48,310 (43,687) 4,623 $ 2,402,355 $ (323,887) $ 2,078,468 $ 567,717 $ (280,442) $ 287,275 (1) Excludes the original cost and related accumulated amortization of fully-amortized intangible assets. Amortization expense related to intangible assets totaled $27.3 million and $8.6 million for the three months ended September 30, 2020 and 2019, respectively, and $45.9 million and $25.7 million for the nine months ended September 30, 2020 and 2019, respectively. The following table sets forth the remaining estimated amortization expense for intangible assets for the next five years and thereafter: For year ending December 31, (In thousands) 2020 $ 26,960 2021 100,459 2022 96,608 2023 95,288 2024 91,870 Thereafter 834,758

EARNINGS PER SHARE

EARNINGS PER SHARE	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
EARNINGS PER SHARE	7. EARNINGS PER SHARE Basic earnings per share is computed by dividing net income attributable to common stockholders by the weighted-average number of common shares outstanding during the periods. Diluted earnings per share is computed by dividing net income attributable to common stockholders 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) 2020 2019 2020 2019 Net income attributable to WESCO International $ 80,678 $ 64,495 $ 80,578 $ 170,329 Less: Preferred stock dividends 14,511 — 15,787 — Net income attributable to common stockholders $ 66,167 $ 64,495 $ 64,791 $ 170,329 Weighted-average common shares outstanding used in computing basic earnings per share 50,043 42,100 44,873 43,545 Common shares issuable upon exercise of dilutive equity awards 444 278 231 355 Weighted-average common shares outstanding and common share equivalents used in computing diluted earnings per share 50,487 42,378 45,104 43,900 Earnings per share attributable to common stockholders Basic $ 1.32 $ 1.53 $ 1.44 $ 3.91 Diluted $ 1.31 $ 1.52 $ 1.44 $ 3.88 For the three and nine months ended September 30, 2020, the computation of diluted earnings per share attributable to common stockholders excluded stock-based awards of approximately 2.0 million and 3.0 million, respectively. For the three and nine months ended September 30, 2019, the computation of diluted earnings per share attributable to common stockholders excluded stock-based awards of approximately 1.8 million. 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. For the three months ended September 30, 2019, the Company received 695,496 shares from an accelerated stock repurchase transaction entered into on May 7, 2019. 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.

DEBT (Notes)

DEBT (Notes)	9 Months Ended
	Sep. 30, 2020
Debt Instrument [Line Items]
Debt Disclosure [Text Block]	DEBT The following table sets forth WESCO's outstanding indebtedness: As of September 30, December 31, (In thousands) International lines of credit $ 29,787 $ 26,255 Accounts Receivable Securitization Facility 890,000 415,000 Revolving Credit Facility 325,000 — 5.375% Senior Notes due 2021 500,000 500,000 5.50% Senior Notes due 2023 58,636 — 5.375% Senior Notes due 2024 350,000 350,000 6.00% Senior Notes due 2025 4,173 — 7.125% Senior Notes due 2025 1,500,000 — 7.250% Senior Notes due 2028, less debt discount of $9,643 1,315,357 — Finance lease obligations 14,891 1,373 Total debt 4,987,844 1,292,628 Plus: Fair value adjustment to the Anixter Senior Notes 1,824 — Less: Unamortized debt issuance costs (82,700) (8,876) Less: Short-term debt and current portion of long-term debt (28,844) (26,685) Total long-term debt $ 4,878,124 $ 1,257,067 Amended and Restated Accounts Receivable Securitization Facility On June 22, 2020, WESCO Distribution amended its accounts receivable securitization facility (the “Receivables Facility”) pursuant to the terms and conditions of a Fifth Amended and Restated Receivables Purchase Agreement (the “Receivables Purchase Agreement”), 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 Purchase Agreement amends and restates the amended and restated receivables purchase agreement entered into on September 24, 2015 (the “Existing Receivables Purchase Agreement”). The Receivables Purchase Agreement, among other things, increased the purchase limit under the Existing Receivables Purchase Agreement from $600 million to $1,025 million, with the opportunity to exercise an accordion feature that permits increases in the purchase limit of up to $375 million, extended the term of the Receivables Facility to June 22, 2023 and added and amended certain defined terms. Borrowings under the Receivables Facility bear interest at the 30-day LIBOR rate, with a LIBOR floor of 0.5%, plus applicable spreads, The interest rate spread of the Receivables Facility increased from 0.95% to 1.20%. The commitment fee remained unchanged at 0.45%. 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. Amended and Restated Asset-Based Revolving Credit Facility On June 22, 2020, WESCO, WESCO Distribution and certain other subsidiaries of WESCO entered into a $1,100 million revolving credit facility (the “Revolving Credit Facility”), as a replacement of WESCO Distribution’s existing revolving credit facility entered into on September 26, 2019, pursuant to the terms and conditions of a Fourth Amended and Restated Credit Agreement, dated as of June 22, 2020 (the “Credit Agreement”), among WESCO Distribution, the other U.S. borrowers party thereto (collectively, the “U.S. Borrowers”), WESCO Distribution Canada LP (“WESCO Canada”), the other Canadian borrowers party thereto (collectively, the “Canadian Borrowers”), WESCO, the lenders party thereto and Barclays Bank PLC, as the administrative agent. The Revolving Credit Facility contains a letter of credit sub-facility of up to $175 million and an accordion feature allowing WESCO Distribution to request increases to the borrowing commitments under the Revolving Credit Facility of up to $500 million in the aggregate, subject to customary conditions. The Revolving Credit Facility matures in June 2025. The obligations of WESCO Distribution and the other U.S. Borrowers under the Revolving Credit Facility have been guaranteed by WESCO and certain of WESCO Distribution’s subsidiaries (including certain subsidiaries of Anxiter Inc.). The obligations of WESCO Canada and the other Canadian Borrowers under the Revolving Credit Facility (including certain subsidiaries of Anxiter Inc.) have been guaranteed by certain subsidiaries of WESCO Canada and the other Canadian Borrowers. The Revolving Credit Facility is secured by (i) substantially all assets of WESCO Distribution, the other U.S. Borrowers and certain of WESCO Distribution’s subsidiaries (including certain subsidiaries of Anxiter Inc.), other than, among other things, real property and accounts receivable sold or intended to be sold pursuant to WESCO Distribution’s Receivables Facility, and (ii) substantially all assets of WESCO Canada, the other Canadian Borrowers and certain of WESCO Canada’s subsidiaries, other than, among other things, real property, in each case, subject to customary exceptions and limitations. 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 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. Upon the occurrence and during the continuance of an event of default, the commitments of the lenders may be terminated, and all outstanding obligations of the loan parties under the Revolving Credit Facility may be declared immediately due and payable. 5.50% Senior Notes due 2023 6.00% Senior Notes due 2025 On April 30, 2020, in connection with the Merger, WESCO Distribution commenced offers to purchase for cash (each, a “WESCO Tender Offer” and, together the “WESCO Tender Offers”) any and all of Anixter Inc.’s outstanding (i) 5.50% Senior Notes due 2023 (the “Anixter 2023 Senior Notes”), $350.0 million aggregate principal amount, issued under the Indenture, dated as of August 18, 2015 (the “Anixter 2023 Indenture”), by and among Anixter Inc., Anixter and Wells Fargo Bank, National Association, as trustee, and (ii) 6.00% Senior Notes due 2025 (the “Anixter 2025 Senior Notes” and, together with the Anixter 2023 Senior Notes, the "Anixter Senior Notes"), $250.0 million aggregate principal amount, issued under the Indenture, dated as of November 13, 2018 (the “Anixter 2025 Indenture” and, together with the Anixter 2023 Indenture, the “Anixter Indentures”) by and among Anixter Inc., Anixter and Wells Fargo Bank, National Association, as trustee. Concurrent with the WESCO Tender Offers, Anixter Inc. commenced consent solicitations to amend the definition of "Change of Control" under the applicable Indenture to exclude the Merger and related transactions and expressly permit a merger between Anixter Inc. and Anixter (the “Anixter Consent Solicitations”). On June 23, 2020 (the "Expiration Date"), following the completion of the Merger, the WESCO Tender Offers and Anixter Consent Solicitations expired and settled. Pursuant to the terms of the Offer to Purchase and Consent Solicitation Statement, dated April 30, 2020, holders of the Anixter Senior Notes that validly tendered and did not validly withdraw prior to such date, received total tender offer consideration of $1,012.50 per $1,000 principal amount of Anixter Senior Notes, which amount, in each case, included an early tender payment of $50.00 per $1,000 principal amount of Anixter Senior Notes. Holders who validly delivered their consents at or prior to the Expiration Date received a consent fee of $2.50 per $1,000 principal amount of Anixter Senior Notes. As of September 30, 2020, $58.6 million and $4.2 million aggregate principal amount of the Anixter 2023 Senior Notes and Anixter 2025 Senior Notes, respectively, were outstanding. 7.125% Senior Notes due 2025 7.250% Senior Notes due 2028 On June 12, 2020, WESCO Distribution issued $1,500 million aggregate principal amount of 7.125% Senior Notes due 2025 (the “2025 Notes”) and $1,325 million aggregate principal amount of 7.250% Senior Notes due 2028 (the “2028 Notes” and, together with the 2025 Notes, the “Notes”). The 2025 Notes were issued at a price of 100.000% of the aggregate principal amount. The 2028 Notes were issued at a price of 99.244% of the aggregate principal amount. The Notes were issued pursuant to, and are governed by, an indenture (the “Notes Indenture”), dated as of June 12, 2020, between the Company, WESCO Distribution and U.S. Bank National Association, as trustee (the “Trustee”). The Notes and related guarantees were issued in a private transaction exempt from the Securities Act of 1933, as amended (the “Securities Act”) and have not been, and will not be, registered under the Securities Act and may not be offered or sold in the United States absent registration or an applicable exemption from, or in a transaction not subject to the registration requirements of the Securities Act and other applicable securities laws. The Company used the net proceeds from the issuance of the Notes, together with borrowings under its new and amended credit facilities and existing cash on hand, to finance the Merger and the other transactions contemplated by the Merger Agreement. The use of proceeds included (i) paying the cash portion of the Merger consideration to stockholders of Anixter, (ii) refinancing certain existing indebtedness of Anixter contemplated by the Merger Agreement, including financing the satisfaction and discharge, defeasance, redemption or other repayment in full of the 5.125% Senior Notes due 2021 of Anixter Inc., a wholly owned subsidiary of Anixter, and financing payments in connection with the Anixter Consent Solicitations and WESCO Tender Offers, as described above, (iii) refinancing other indebtedness of the Company, and (iv) paying fees, costs and expenses in connection with the foregoing. The Notes are unsecured and unsubordinated obligations of WESCO Distribution and are guaranteed on an unsecured, unsubordinated basis by the Company and Anixter Inc. The 2025 Notes accrue interest at a rate of 7.125% per annum, payable semi-annually in arrears on June 15 and December 15 of each year, beginning on December 15, 2020. The 2025 Notes will mature on June 15, 2025. The 2028 Notes accrue interest at a rate of 7.250% per annum, payable semi-annually in arrears on June 15 and December 15 of each year, beginning on December 15, 2020. The 2028 Notes will mature on June 15, 2028. WESCO Distribution may redeem all or a part of the 2025 Notes at any time prior to June 15, 2022 by paying a “make-whole” premium plus accrued and unpaid interest, if any, to but excluding the redemption date. In addition, at any time prior to June 15, 2022, WESCO Distribution may redeem up to 35% of the 2025 Notes with the net cash proceeds from certain equity offerings. On or after June 15, 2022, WESCO Distribution may redeem all or a part of the 2025 Notes on the redemption dates and at the redemption prices specified in the Notes Indenture. WESCO Distribution may redeem all or a part of the 2028 Notes at any time prior to June 15, 2023 by paying a “make-whole” premium plus accrued and unpaid interest, if any, to but excluding the redemption date. In addition, at any time prior to June 15, 2023, WESCO Distribution may redeem up to 35% of the 2028 Notes with the net cash proceeds from certain equity offerings. On or after June 15, 2023, WESCO Distribution may redeem all or a part of the 2028 Notes on the redemption dates and at the redemption prices specified in the Notes Indenture. The Notes Indenture contains certain covenants that, among other things, limit (i) the Company’s and its subsidiaries’ ability to pay dividends on or repurchase the Company’s capital stock, incur liens on assets, engage in certain sale and leaseback transactions or sell certain assets, and (ii) the Company’s and any guarantor’s ability to sell all or substantially all of its assets to, or merge or consolidate with or into, other persons, in the case of each of the foregoing, subject to certain qualifications and exceptions, including the termination of certain of these covenants upon the Notes receiving investment grade credit ratings. The Notes Indenture contains certain events of default, including, among other things, failure to make required payments, failure to comply with certain agreements or covenants, failure to pay or acceleration of certain other indebtedness, certain events of bankruptcy and insolvency, and failure to pay certain judgments. An event of default under the Notes Indenture will allow either the Trustee or the holders of at least 25% in aggregate principal amount of the applicable series of the then-outstanding Notes to accelerate, or in certain cases, will automatically cause the acceleration of the amounts due under the applicable series of Notes.

STOCK-BASED COMPENSATION (Notes

STOCK-BASED COMPENSATION (Notes)	9 Months Ended
	Sep. 30, 2020
Share-based Payment Arrangement [Abstract]
STOCK-BASED COMPENSATION	6. 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 is determined using the Black-Scholes model. 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. Except for the special award described below, 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. On July 2, 2020, a special award of restricted stock units was granted to certain officers of the Company. These awards vest in tranches of 30% on each of the first and second anniversaries of the grant date and 40% on the third anniversary of the grant date, subject, in each case, to continued employment through the applicable anniversary date. Performance-based awards granted in 2020 and 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. During the three and nine months ended September 30, 2020 and 2019, WESCO granted the following stock-settled stock appreciation rights, restricted stock units and performance-based awards at the following weighted-average fair values: Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, Stock-settled stock appreciation rights granted — — 262,091 213,618 Weighted-average fair value $ — $ — $ 13.86 $ 16.36 Restricted stock units granted 444,375 6,256 655,825 181,800 Weighted-average fair value $ 32.18 $ 47.95 $ 37.38 $ 54.41 Performance-based awards granted — — 158,756 126,874 Weighted-average fair value $ — $ — $ 48.67 $ 54.64 The fair value of stock-settled stock appreciation rights was estimated using the following weighted-average assumptions: Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, Risk free interest rate n/a n/a 1.4 % 2.5 % Expected life (in years) n/a n/a 5 5 Expected volatility n/a n/a 30 % 29 % The risk-free interest rate is based on the U.S. Treasury Daily Yield Curve as of the grant date. The expected life is based on historical exercise experience and the expected volatility is based on the volatility of the Company's daily stock prices over a five-year period preceding the grant date. The following table sets forth a summary of stock-settled stock appreciation rights and related information for the nine months ended September 30, 2020: Awards Weighted- Weighted- Aggregate Outstanding at December 31, 2019 2,337,049 $ 59.72 Granted 262,091 48.32 Exercised (182,487) 33.57 Forfeited (39,112) 65.57 Outstanding at September 30, 2020 2,377,541 60.37 5.7 $ 679 Exercisable at September 30, 2020 1,844,929 $ 62.32 5.0 $ 679 The following table sets forth a summary of time-based restricted stock units and related information for the nine months ended September 30, 2020: Awards Weighted- Unvested at December 31, 2019 363,729 $ 60.00 Granted 655,825 37.38 Vested (80,486) 69.68 Forfeited (8,364) 60.03 Unvested at September 30, 2020 930,704 $ 43.23 The following table sets forth a summary of performance-based awards for the nine months ended September 30, 2020: Awards Weighted- Unvested at December 31, 2019 195,305 $ 60.24 Granted 158,756 48.67 Vested (25,909) 78.04 Forfeited (20,538) 71.47 Unvested at September 30, 2020 307,614 $ 52.60 Vesting of the 307,614 shares of performance-based awards in the table above is dependent upon the achievement of certain performance targets, including 134,010 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 153,807 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 $6.0 million and $4.4 million of non-cash stock-based compensation expense, which is included in selling, general and administrative expenses, for the three months ended September 30, 2020 and 2019, respectively. WESCO recognized $15.5 million and $14.2 million of non-cash stock-based compensation expense, which is included in selling, general and administrative expenses, for the nine months ended September 30, 2020 and 2019, respectively. As of September 30, 2020, there was $39.8 million of unrecognized compensation cost related to non-vested stock-based compensation arrangements for all awards previously made, of which $6.0 million is expected to be recognized over the remainder of 2020, $17.8 million in 2021, $12.4 million in 2022 and $3.6 million in 2023.

Equity

Equity	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Stockholders' Equity Note Disclosure	9. STOCKHOLDERS' EQUITY Series A Preferred Stock The Company's Board of Directors authorized 25,000 shares of fixed-rate reset cumulative perpetual preferred stock, Series A, with a liquidation preference of $25,000 per whole preferred share and a par value of $0.01 per share (the "Series A Preferred Stock"). Depositary shares, each representing a 1/1,000th interest in a share of Series A Preferred Stock, are registered under the Securities Act of 1933, as amended. In connection with the Merger, as described in Note 4, the Company issued 21,611,534 depositary shares, representing an interest in approximately 21,612 shares of Series A Preferred Stock. Holders of shares of the Series A Preferred Stock are entitled to receive, when, as and if declared by the Company's Board of Directors, cumulative cash dividends at an initial rate of 10.625% per annum of the $25,000 liquidation preference per share. On June 22, 2025, and every five-year period thereafter, the dividend rate on the Series A Preferred Stock resets and will be equal to the Five-year U.S. Treasury Rate plus a spread of 10.325%. Holders of the Series A Preferred Stock are not entitled to convert or exchange their shares of Series A Preferred stock into shares of any of WESCO’s other classes or series of stock or into any other security of WESCO (other than upon a change of control involving the issuance of additional shares of common stock or other change of control transaction, in each case, approved by holders of common stock). The Series A Preferred Stock has no stated maturity and will not be subject to any sinking fund, retirement fund or purchase fund or any other obligation of WESCO to redeem, repurchase or retire the Series A Preferred Stock. Holders of the Series A Preferred Stock will have limited voting rights, including the right to elect two directors to the board of directors of the Company in the event dividends on the Series A Preferred Stock remain unpaid for the equivalent of six or more full quarterly dividend periods. Stockholder Rights Plan On July 17, 2020, WESCO's Board of Directors declared a dividend of one preferred share purchase right (a “Right”) for each outstanding share of common stock of WESCO, par value $0.01 per share (“WESCO Common Stock”), and adopted a stockholder rights plan, as set forth in the Rights Agreement, dated as of July 17, 2020 (the “Rights Agreement”), by and between WESCO and Computershare Trust Company, N.A., as rights agent. In general terms, the Rights Agreement works by imposing a significant penalty upon any person or group which acquires 10% or more (15% or more in the case of passive investors filing statements on Schedule 13G) of the outstanding WESCO Common Stock without the approval of the Board. The dividend Right was paid on July 27, 2020 to WESCO stockholders of record as of the close of business on July 27, 2020. The Rights Agreement provides that the Rights will expire on July 16, 2021. The Rights have no value upon issuance.

EMPLOYEE BENEFIT PLANS (Notes)

EMPLOYEE BENEFIT PLANS (Notes)	9 Months Ended
	Sep. 30, 2020
Retirement Benefits [Abstract]
EMPLOYEE BENEFIT PLANS	10. PENSION PLANS, POST-RETIREMENT BENEFITS AND OTHER BENEFITS Defined Contribution Plans WESCO Distribution sponsors a defined contribution retirement savings plan for the majority of its U.S. employees. The Company matches contributions made by employees at an amount equal to 50% of participants' total monthly contributions up to 6% of eligible compensation. Contributions are made in cash and employees have the option to transfer balances allocated to their accounts into any of the available investment options. The Company 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. Due to the COVID-19 pandemic and its adverse effect on WESCO's results of operations, the Company suspended matching employer contributions between April 16, 2020 and September 30, 2020. WESCO Distribution Canada LP, a wholly-owned subsidiary of the Company, sponsors a defined contribution plan for certain Canadian employees. The Company makes contributions in amounts ranging from 3% to 5% of participants' eligible compensation based on years of continuous service. Anixter Inc. sponsors a defined contribution plan covering all of its non-union U.S. employees (the "Anixter Employee Savings Plan"). The employer match for the Anixter Employee Savings Plan is equal to 50% of a participant's contribution up to 5% of the participant's compensation. Anixter Inc. will also make an annual contribution to the Anixter Employee Savings Plan on behalf of each active participant who is hired or rehired on or after July 1, 2015, or is not participating in the Anixter Inc. Pension Plan. The amount of the employer annual contribution is equal to either 2% or 2.5% of the participant’s compensation, as determined by the participant’s years of service. This contribution is in lieu of being eligible for the Anixter Inc. Pension Plan. Certain of Anixter Inc.'s foreign subsidiaries also have defined contribution plans. Contributions to these plans are based upon various levels of employee participation and legal requirements. Deferred Compensation Plans WESCO Distribution sponsors a deferred compensation plan (the "WESCO Deferred Compensation Plan") that permits select employees to make pre-tax deferrals of salary and bonus. Employees have the option to transfer balances allocated to their accounts in the WESCO Deferred Compensation Plan into any of the available investment options. The WESCO Deferred Compensation Plan is an unfunded plan. As of September 30, 2020, the Company's obligation under the WESCO Deferred Compensation Plan was $26.0 million, of which $10.1 million was included in other current liabilities and $15.9 million in other noncurrent liabilities in the Condensed Consolidated Balance Sheet. At December 31, 2019, the Company's obligation under the WESCO Deferred Compensation Plan was $25.2 million, which was included in other noncurrent liabilities in the Condensed Consolidated Balance Sheet. Anixter Inc. sponsors a non-qualified deferred compensation plan (the "Anixter Deferred Compensation Plan") that permits select employees to make pre-tax deferrals of salary and bonus. Interest is accrued monthly on the deferred compensation balances based on the average ten-year Treasury note rate for the previous three months times a factor of 1.4, and the rate is further adjusted if certain financial goals are achieved. At September 30, 2020, the deferred compensation liabilities included in other current liabilities and other noncurrent liabilities in the Condensed Consolidated Balance Sheet were $3.8 million and $42.4 million, respectively. Concurrent with the implementation of the Anixter Deferred Compensation Plan, the Company established a Rabbi Trust arrangement to provide for the liabilities associated with the deferred compensation plan and an executive non-qualified defined benefit plan. The assets are invested in marketable securities. At September 30, 2020, $39.5 million was recorded in other assets in the Condensed Consolidated Balance Sheet for this arrangement. Defined Benefit Plans WESCO sponsors a contributory defined benefit plan covering substantially all Canadian employees of EECOL Electric Corp. (""EECOL") and a Supplemental Executive Retirement Plan for certain executives of EECOL (the "EECOL SERP"). Anixter Inc. sponsors defined benefit pension plans in the U.S., which consist of the Anixter Inc. Pension Plan, the Executive Benefit Plan and the Supplemental Executive Retirement Plan (the "Anixter SERP") (together, the "Anixter Domestic Plans") and various defined benefit pension plans covering employees of foreign subsidiaries in Canada and Europe (together, the " Anixter Foreign Plans"). The Anixter Inc. Pension Plan was frozen to entrants first hired or rehired on or after July 1, 2015. The majority of these defined benefit pension plans are non-contributory, and with the exception of U.S. and Canada, cover substantially all full-time domestic employees and certain employees in other countries. Retirement benefits are provided based on compensation as defined in both the Anixter Domestic Plans and the Anixter Foreign Plans. The Anixter Domestic Plans are funded as required by the Employee Retirement Income Security Act of 1974 ("ERISA") and the IRS and all Anixter Foreign Plans are funded as required by applicable foreign laws. The Anixter Inc. Executive Benefit Plan and the Anixter SERP are unfunded plans. During the three and nine months ended September 30, 2020, the Company made aggregate cash contributions of $2.9 million and $4.7 million, respectively, for all of the benefit plans described above. For the nine months ended September 30, 2020 and 2019, WESCO incurred total charges of $13.6 million and $24.7 million, respectively, for all of the benefit plans described above. The following table sets forth the components of net periodic benefit costs for the Company's defined benefit plans: Three Months Ended Nine Months Ended September 30 September 30 (In thousands) 2020 2019 2020 2019 Service cost $ 3,826 $ 1,158 $ 6,801 $ 3,446 Interest cost 4,844 1,098 7,170 3,267 Expected return on plan assets (8,399) (1,433) (12,001) (4,265) Recognized actuarial gain (1) (1) (16) 52 (47) Net periodic benefit cost $ 270 $ 807 $ 2,022 $ 2,401 (1) For the three and nine months ended September 30, 2020 and 2019, no amounts were reclassified from accumulated other comprehensive income into net income, respectively. The service cost of $3.8 million and $1.2 million for the three months ended September 30, 2020 and 2019, respectively, and $6.8 million and $3.4 million for the nine months ended September 30, 2020 and 2019, respectively, is reported as a component of selling, general and administrative expenses. The other components of net periodic benefit cost totaling a net benefit of $3.6 million and $0.4 million for the three months ended September 30, 2020 and 2019, respectively, and $4.8 million and $1.0 million for the nine months ended September 30, 2020 and 2019, respectively, are presented as a component of other non-operating expenses ("other, net"). Other Benefits As permitted by the Merger Agreement, Anixter granted restricted stock units prior to June 22, 2020 in the ordinary course of business to its employees and directors. These awards, which did not accelerate solely as a result of the Merger, were converted into cash-only settled WESCO phantom stock units, which vest ratably over a 3-year period. As of September 30, 2020, the estimated fair value of these awards was $13.4 million. The Company recognized compensation expense associated with these awards of $1.4 million and $2.3 million for the three and nine months ended September 30, 2020, respectively, which is reported as a component of selling, general and administrative expenses.
STOCK-BASED COMPENSATION	6. 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 is determined using the Black-Scholes model. 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. Except for the special award described below, 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. On July 2, 2020, a special award of restricted stock units was granted to certain officers of the Company. These awards vest in tranches of 30% on each of the first and second anniversaries of the grant date and 40% on the third anniversary of the grant date, subject, in each case, to continued employment through the applicable anniversary date. Performance-based awards granted in 2020 and 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. During the three and nine months ended September 30, 2020 and 2019, WESCO granted the following stock-settled stock appreciation rights, restricted stock units and performance-based awards at the following weighted-average fair values: Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, Stock-settled stock appreciation rights granted — — 262,091 213,618 Weighted-average fair value $ — $ — $ 13.86 $ 16.36 Restricted stock units granted 444,375 6,256 655,825 181,800 Weighted-average fair value $ 32.18 $ 47.95 $ 37.38 $ 54.41 Performance-based awards granted — — 158,756 126,874 Weighted-average fair value $ — $ — $ 48.67 $ 54.64 The fair value of stock-settled stock appreciation rights was estimated using the following weighted-average assumptions: Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, Risk free interest rate n/a n/a 1.4 % 2.5 % Expected life (in years) n/a n/a 5 5 Expected volatility n/a n/a 30 % 29 % The risk-free interest rate is based on the U.S. Treasury Daily Yield Curve as of the grant date. The expected life is based on historical exercise experience and the expected volatility is based on the volatility of the Company's daily stock prices over a five-year period preceding the grant date. The following table sets forth a summary of stock-settled stock appreciation rights and related information for the nine months ended September 30, 2020: Awards Weighted- Weighted- Aggregate Outstanding at December 31, 2019 2,337,049 $ 59.72 Granted 262,091 48.32 Exercised (182,487) 33.57 Forfeited (39,112) 65.57 Outstanding at September 30, 2020 2,377,541 60.37 5.7 $ 679 Exercisable at September 30, 2020 1,844,929 $ 62.32 5.0 $ 679 The following table sets forth a summary of time-based restricted stock units and related information for the nine months ended September 30, 2020: Awards Weighted- Unvested at December 31, 2019 363,729 $ 60.00 Granted 655,825 37.38 Vested (80,486) 69.68 Forfeited (8,364) 60.03 Unvested at September 30, 2020 930,704 $ 43.23 The following table sets forth a summary of performance-based awards for the nine months ended September 30, 2020: Awards Weighted- Unvested at December 31, 2019 195,305 $ 60.24 Granted 158,756 48.67 Vested (25,909) 78.04 Forfeited (20,538) 71.47 Unvested at September 30, 2020 307,614 $ 52.60 Vesting of the 307,614 shares of performance-based awards in the table above is dependent upon the achievement of certain performance targets, including 134,010 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 153,807 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 $6.0 million and $4.4 million of non-cash stock-based compensation expense, which is included in selling, general and administrative expenses, for the three months ended September 30, 2020 and 2019, respectively. WESCO recognized $15.5 million and $14.2 million of non-cash stock-based compensation expense, which is included in selling, general and administrative expenses, for the nine months ended September 30, 2020 and 2019, respectively. As of September 30, 2020, there was $39.8 million of unrecognized compensation cost related to non-vested stock-based compensation arrangements for all awards previously made, of which $6.0 million is expected to be recognized over the remainder of 2020, $17.8 million in 2021, $12.4 million in 2022 and $3.6 million in 2023.
Compensation Related Costs, General	Other Benefits As permitted by the Merger Agreement, Anixter granted restricted stock units prior to June 22, 2020 in the ordinary course of business to its employees and directors. These awards, which did not accelerate solely as a result of the Merger, were converted into cash-only settled WESCO phantom stock units, which vest ratably over a 3-year period. As of September 30, 2020, the estimated fair value of these awards was $13.4 million. The Company recognized compensation expense associated with these awards of $1.4 million and $2.3 million for the three and nine months ended September 30, 2020, respectively, which is reported as a component of selling, general and administrative expenses.

FAIR VALUE (Notes)

FAIR VALUE (Notes)	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
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 carrying value of WESCO's debt instruments with fixed interest rates was $3,730.0 million and $850.0 million as of September 30, 2020 and December 31, 2019, respectively. The estimated fair value of this debt was $4,015.6 million and $866.2 million, respectively. The reported carrying values of WESCO's other financial instruments, including indebtedness with variable interest rates, approximated their fair values as of September 30, 2020 and December 31, 2019. The Company purchases foreign currency forward contracts to minimize the effect of fluctuating foreign currency-denominated accounts on its reported income. The foreign currency forward contracts are not designated as hedges for accounting purposes. The Company's strategy is to negotiate terms for its derivatives and other financial instruments to be highly effective, such that the change in the value of the derivative offsets the impact of the underlying hedge. Its counterparties to foreign currency forward contracts have investment-grade credit ratings. The Company regularly monitors the creditworthiness of its counterparties to ensure no issues exist which could affect the value of the derivatives. The Company does not hedge 100% of its foreign currency-denominated accounts. In addition, the results of hedging can vary significantly based on various factors, such as the timing of executing foreign currency forward contracts versus the movement of currencies as well as the fluctuations in the account balances throughout each reporting period. The fair value of foreign currency forward contracts is based on the difference between the contract rate and the current exchange rate. The fair value of foreign currency forward contracts is measured using observable market information. These inputs would be considered Level 2 in the fair value hierarchy. At September 30, 2020, foreign currency forward contracts were revalued at then-current foreign exchange rates with the changes in valuation reflected directly in other non-operating expenses ("other, net") in the Condensed Consolidated Statements of Income and Comprehensive Income offsetting the transaction gain (loss) recorded on foreign currency-denominated accounts. At September 30, 2020, the gross and net notional amounts of foreign currency forward contracts outstanding were approximately $104.8 million. While all of the Company's foreign currency forward contracts are subject to master netting arrangements with its counterparties, assets and liabilities related to these contracts are presented on a gross basis within the Condensed Consolidated Balance Sheets. The gross fair value of assets and liabilities related to foreign currency forward contracts were immaterial.
Derivatives and Fair Value	The Company purchases foreign currency forward contracts to minimize the effect of fluctuating foreign currency-denominated accounts on its reported income. The foreign currency forward contracts are not designated as hedges for accounting purposes. The Company's strategy is to negotiate terms for its derivatives and other financial instruments to be highly effective, such that the change in the value of the derivative offsets the impact of the underlying hedge. Its counterparties to foreign currency forward contracts have investment-grade credit ratings. The Company regularly monitors the creditworthiness of its counterparties to ensure no issues exist which could affect the value of the derivatives. The Company does not hedge 100% of its foreign currency-denominated accounts. In addition, the results of hedging can vary significantly based on various factors, such as the timing of executing foreign currency forward contracts versus the movement of currencies as well as the fluctuations in the account balances throughout each reporting period. The fair value of foreign currency forward contracts is based on the difference between the contract rate and the current exchange rate. The fair value of foreign currency forward contracts is measured using observable market information. These inputs would be considered Level 2 in the fair value hierarchy. At September 30, 2020, foreign currency forward contracts were revalued at then-current foreign exchange rates with the changes in valuation reflected directly in other non-operating expenses ("other, net") in the Condensed Consolidated Statements of Income and Comprehensive Income offsetting the transaction gain (loss) recorded on foreign currency-denominated accounts. At September 30, 2020, the gross and net notional amounts of foreign currency forward contracts outstanding were approximately $104.8 million. While all of the Company's foreign currency forward contracts are subject to master netting arrangements with its counterparties, assets and liabilities related to these contracts are presented on a gross basis within the Condensed Consolidated Balance Sheets. The gross fair value of assets and liabilities related to foreign currency forward contracts were immaterial.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	9 Months Ended
	Sep. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	. 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 debt facilities comprised of a $5.8 million term loan and a $1.0 million line of credit 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 debt facilities. As of September 30, 2020, WESTEC had outstanding indebtedness totaling $6.0 million. Management currently believes the estimated fair value of the noncontingent guarantee on the outstanding indebtedness is nominal and therefore a liability has not been recorded as of September 30, 2020.

INCOME TAXES

INCOME TAXES	9 Months Ended
	Sep. 30, 2020
Income Tax Disclosure [Abstract]
INCOME TAXES	13. INCOME TAXES The effective tax rate for the three and nine months ended September 30, 2020 was 23.3% and 22.9%, respectively. The effective tax rate for the three and nine months ended September 30, 2019 was 19.8% and 21.0%, 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 corresponding prior year periods primarily due to expenses incurred by WESCO to complete the acquisition of Anixter. There have been no material adjustments to liabilities for uncertain tax positions since the last annual disclosure, except for preliminary amounts recorded in connection with the acquisition of Anixter, which totaled $30.0 million. In addition, the Company reassessed the realizability of certain deferred income tax assets acquired, including Anixter’s foreign tax credit carryforwards. As a result, the Company preliminary allocated $59.4 million to a foreign tax credit carryforward and $41.4 million to the related valuation allowance.

Segment Reporting

Segment Reporting	9 Months Ended
	Sep. 30, 2020
Segment Reporting [Abstract]
Segment Reporting Disclosure	14. BUSINESS SEGMENTS Prior to the completion of its merger with Anixter on June 22, 2020, as described in Note 4, WESCO had four operating segments that had been aggregated as one reportable segment. Effective on the date of acquisition, the Company added Anixter as a separate reportable segment for the quarterly period ended June 30, 2020. In the third quarter, the Company identified new operating segments organized around three strategic business units consisting of EES, CSS and UBS. These operating segments are equivalent to the Company's reportable segments. The operating segments in the respective periods were determined in accordance with the manner in which WESCO's chief operating decision maker ("CODM") reviewed financial information during those periods. The following is a description of each of the Company's reportable segments and their business activities. Electrical & Electronic Solutions The EES segment supplies a broad range of products and supply chain solutions primarily to the Construction, Industrial and Original Equipment Manufacturer ("OEM") markets. Product categories include a broad range of electrical equipment and supplies as well as lubricants, pipe, valves, fittings, fasteners, cutting tools, power transmission, and safety products. In addition, OEM customers require a reliable supply of assemblies and components to incorporate into their own products as well as value-added services such as supplier consolidation, design and technical support, just-in-time supply and electronic commerce, and supply chain management. EES includes the “Electrical and Electronic Solutions” business acquired from Anixter and the majority of the legacy WESCO industrial and construction businesses. Communications & Security Solutions The CSS segment supplies products and customized supply chain solutions to customers in a diverse range of industries including technology, finance, telecommunications service providers, transportation, education, government, healthcare and retail. CSS sells these products directly to end users or through various channels including data communications contractors, security, network, professional audio/visual and systems integrators. CSS has a broad product portfolio that includes copper and fiber optic cable and connectivity, access control, video surveillance, intrusion and fire/life safety, cabinets, power, cable management, wireless, professional audio/video, voice and networking switches and other ancillary products. CSS includes the “Network and Security Solutions” business acquired from Anixter and the legacy data communications and safety businesses from WESCO. Utility & Broadband Solutions The UBS segment supplies electrical transmission and distribution products, power plant maintenance, repair and operations supplies and smart-grid products, and arranges materials management and procurement outsourcing for the power generation, power transmission and electricity distribution industries. The UBS segment combines the “Utility Power Solutions” business acquired from Anixter, the WESCO utility business, a portion of the legacy WESCO broadband business as well as the legacy WESCO integrated supply business. Corporate expenses are incurred to obtain and coordinate financing, tax, information technology, legal and other related services. The Company also has various corporate assets which are reported in corporate. Segment assets may not include jointly used assets, but segment results include depreciation expense or other allocations related to those assets. Interest expense and other non-operating items are not allocated to the segments or reviewed on a segment basis. Corporate expenses and assets are shown in the tables below to reconcile the reportable segments to the consolidated financial statements. For the three and nine months ended September 30, 2020 and September 30, 2019, the Company's CODM evaluated the performance of its operating segments based primarily on net sales, income from operations, and total assets. The following table sets forth net sales and income from operations by reportable segment for the periods presented: (In thousands) Three Months Ended September 30, 2020 EES CSS UBS Corporate Total Net sales $ 1,653,726 $ 1,388,791 $ 1,099,284 $ — $ 4,141,801 Income from operations 105,508 89,634 74,092 (91,139) 178,095 Three Months Ended September 30, 2019 (In thousands) EES CSS UBS Corporate Total Net sales $ 1,250,080 $ 235,920 $ 662,110 $ — $ 2,148,110 Income from operations 72,007 10,555 43,811 (32,640) 93,733 Nine Months Ended September 30, 2020 (In thousands) EES CSS UBS Corporate Total Net sales $ 3,811,498 $ 1,953,967 $ 2,431,689 $ — $ 8,197,154 Income from operations 194,643 127,502 167,651 (235,518) 254,278 Nine Months Ended September 30, 2019 (In thousands) EES CSS UBS Corporate Total Net sales $ 3,626,423 $ 681,087 $ 1,951,955 $ — $ 6,259,465 Income from operations 198,774 32,501 134,431 (103,297) 262,409 The following table sets forth total assets by reportable segment for the periods presented: As of September 30, 2020 (In thousands) EES CSS UBS Corporate (1) Total Total assets $ 3,838,242 $ 4,592,463 $ 2,990,621 $ 447,013 $ 11,868,339 As of December 31, 2019 (In thousands) EES CSS UBS Corporate (1) Total Total assets $ 2,523,481 $ 610,046 $ 1,747,809 $ 136,299 $ 5,017,635 (1) Total assets for Corporate primarily consist of cash and cash equivalents, deferred income taxes, fixed assets and leases.

ACCOUNTING POLICIES (Policies)

ACCOUNTING POLICIES (Policies)	9 Months Ended
	Sep. 30, 2020
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 2019 Annual Report on Form 10-K as filed with the SEC on February 24, 2020. The Condensed Consolidated Balance Sheet at December 31, 2019 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, 2020, the unaudited Condensed Consolidated Statements of Income and Comprehensive Income, the unaudited Condensed Consolidated Statements of Stockholders' Equity for the three and nine months ended September 30, 2020 and 2019, and the unaudited Condensed Consolidated Statements of Cash Flows for the nine months ended September 30, 2020 and 2019, 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. In the third quarter of 2020, in connection with the acquisition of Anixter, the Company identified new operating segments. These operating segments, which have been organized around three strategic business units, consist of Electrical & Electronic Solutions ("EES"), Communications & Security Solutions ("CSS") and Utility & Broadband Solutions ("UBS"). The Company's operating segments, which are equivalent to its reportable segments, are described further in Note 14. The applicable comparative financial information reported in the Company's previously issued interim financial statements for the three and nine months ended September 30, 2019 has been recast in this Quarterly Report on Form 10-Q to conform to the basis of the new segments.
New Accounting Pronouncements and Changes in Accounting Principles [Text Block]	Recently Adopted Accounting Pronouncements In June 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , which introduced new guidance for the accounting for credit losses on certain financial instruments. The Company adopted this ASU effective January 1, 2020. The adoption of this new credit loss guidance did not have a material impact on the unaudited condensed consolidated financial statements and notes thereto presented herein, and WESCO does not expect it to have a material impact on its financial position or results of operation on an ongoing basis. 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 Company adopted this ASU in the first quarter of 2020. The adoption of this guidance did not have a material impact on the unaudited condensed consolidated financial statements and notes thereto presented herein. In August 2018, the FASB issued ASU 2018-15, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract , which aligned the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The standard was effective for fiscal years beginning after December 15, 2019. The Company adopted this ASU in the first quarter of 2020. The adoption of this guidance did not have a material impact on the unaudited condensed consolidated financial statements and notes thereto presented herein.
Reclassifications [Text Block]	Reclassifications The Condensed Consolidated Balance Sheet as of December 31, 2019, the unaudited Condensed Consolidated Statements of Income and Comprehensive Income for the three and nine months ended September 30, 2019, and the unaudited Condensed Consolidated Statement of Cash Flows for the nine months ended September 30, 2019, respectively, include 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 carrying value of WESCO's debt instruments with fixed interest rates was $3,730.0 million and $850.0 million as of September 30, 2020 and December 31, 2019, respectively. The estimated fair value of this debt was $4,015.6 million and $866.2 million, respectively. The reported carrying values of WESCO's other financial instruments, including indebtedness with variable interest rates, approximated their fair values as of September 30, 2020 and December 31, 2019. The Company purchases foreign currency forward contracts to minimize the effect of fluctuating foreign currency-denominated accounts on its reported income. The foreign currency forward contracts are not designated as hedges for accounting purposes. The Company's strategy is to negotiate terms for its derivatives and other financial instruments to be highly effective, such that the change in the value of the derivative offsets the impact of the underlying hedge. Its counterparties to foreign currency forward contracts have investment-grade credit ratings. The Company regularly monitors the creditworthiness of its counterparties to ensure no issues exist which could affect the value of the derivatives. The Company does not hedge 100% of its foreign currency-denominated accounts. In addition, the results of hedging can vary significantly based on various factors, such as the timing of executing foreign currency forward contracts versus the movement of currencies as well as the fluctuations in the account balances throughout each reporting period. The fair value of foreign currency forward contracts is based on the difference between the contract rate and the current exchange rate. The fair value of foreign currency forward contracts is measured using observable market information. These inputs would be considered Level 2 in the fair value hierarchy. At September 30, 2020, foreign currency forward contracts were revalued at then-current foreign exchange rates with the changes in valuation reflected directly in other non-operating expenses ("other, net") in the Condensed Consolidated Statements of Income and Comprehensive Income offsetting the transaction gain (loss) recorded on foreign currency-denominated accounts. At September 30, 2020, the gross and net notional amounts of foreign currency forward contracts outstanding were approximately $104.8 million. While all of the Company's foreign currency forward contracts are subject to master netting arrangements with its counterparties, assets and liabilities related to these contracts are presented on a gross basis within the Condensed Consolidated Balance Sheets. The gross fair value of assets and liabilities related to foreign currency forward contracts were immaterial.
New Accounting Pronouncements, Policy [Policy Text Block]	Recently Issued Accounting Pronouncements 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 condensed consolidated financial statements and notes thereto. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes , which removes certain exceptions to the general principles of Accounting Standards Codification Topic 740, Income Taxes , and simplifies other aspects of accounting for income taxes. The amendments in this ASU are effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020. Early adoption is permitted in any interim or annual period, with any adjustments reflected as of the beginning of the fiscal year of adoption. Management does not expect the adoption of this accounting standard to have a material impact on its condensed consolidated financial statements and notes thereto. In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting , which provides optional guidance for a limited period of time to ease the potential burden in accounting for (or recognizing the effects of) reference rate reform on financial reporting. The amendments in this Update are effective for all entities as of March 12, 2020 through December 31, 2022. Management is currently evaluating the impact related to the replacement of London Interbank Offered Rate (LIBOR) and whether the Company will elect the adoption of the optional guidance. 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.

COMMITMENTS AND CONTINGENCIES G

COMMITMENTS AND CONTINGENCIES Guarantee (Policies)	9 Months Ended
	Sep. 30, 2020
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 debt facilities comprised of a $5.8 million term loan and a $1.0 million line of credit 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 debt facilities. As of September 30, 2020, WESTEC had outstanding indebtedness totaling $6.0 million. Management currently believes the estimated fair value of the noncontingent guarantee on the outstanding indebtedness is nominal and therefore a liability has not been recorded as of September 30, 2020.

REVENUE (Tables)

REVENUE (Tables)	9 Months Ended
	Sep. 30, 2020
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue [Table Text Block]	The following tables disaggregate WESCO’s net sales by segment and geography for the periods presented: Three Months Ended Nine Months Ended September 30 September 30 (In thousands) 2020 2019 2020 2019 Electrical & Electronic Solutions $ 1,653,726 $ 1,250,080 $ 3,811,498 $ 3,626,423 Communications & Security Solutions 1,388,791 235,920 1,953,967 681,087 Utility & Broadband Solutions 1,099,284 662,110 2,431,689 1,951,955 Total by segment $ 4,141,801 $ 2,148,110 $ 8,197,154 $ 6,259,465 Three Months Ended Nine Months Ended September 30 September 30 (In thousands) 2020 2019 2020 2019 United States $ 3,033,101 $ 1,601,962 $ 6,100,877 $ 4,679,251 Canada 582,700 431,233 1,311,724 1,230,855 Other International 526,000 114,915 784,553 349,359 Total by geography (1) $ 4,141,801 $ 2,148,110 $ 8,197,154 $ 6,259,465

ACQUISITIONS (Tables)

ACQUISITIONS (Tables)	9 Months Ended
	Sep. 30, 2020
Business Combinations [Abstract]
Business Acquisition, Schedule of Consideration Transferred	The total preliminary estimated fair value of consideration transferred for the Merger consisted of the following: (In thousands) Cash portion attributable to common stock outstanding $ 2,476,010 Cash portion attributable to options and restricted stock units outstanding 87,375 Fair value of cash consideration 2,563,385 Common stock consideration 313,512 Series A preferred stock consideration 573,786 Fair value of equity consideration 887,298 Extinguishment of Anixter obligations, including accrued and unpaid interest 1,247,653 Total purchase consideration $ 4,698,336 Supplemental cash flow disclosure related to acquisitions: Cash paid for acquisition $ 3,811,038 Less: Cash acquired (103,463) Cash paid for acquisition, net of cash acquired $ 3,707,575
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	The following table sets forth the preliminary allocation of the purchase consideration to the respective fair value of assets acquired and liabilities assumed for the acquisition of Anixter: (In thousands) Assets Cash and cash equivalents $ 103,463 Trade accounts receivable 1,309,104 Other accounts receivable 116,386 Inventories 1,424,678 Prepaid expenses and other current assets 53,462 Property, buildings and equipment 213,020 Operating lease assets 262,413 Intangible assets 1,838,065 Goodwill 1,360,373 Other assets 112,386 Total assets $ 6,793,350 Liabilities Accounts payable $ 920,163 Accrued payroll and benefit costs 69,480 Short-term debt and current portion of long-term debt 13,225 Other current liabilities 222,615 Long-term debt 77,822 Operating lease liabilities 199,959 Deferred income taxes 384,890 Other noncurrent liabilities 206,860 Total liabilities $ 2,095,014 Fair value of net assets acquired, including goodwill and intangible assets $ 4,698,336
Finite-Lived and Indefinite-Lived Intangible Assets Acquired as Part of Business Combination	The following table sets forth the preliminary identifiable intangible assets and their estimated weighted-average useful lives: Identifiable Intangible Assets Estimated Weighted-Average Estimated Useful Life in Years (In thousands) Customer relationships $ 1,098,900 16 Trademarks 735,000 Indefinite Non-compete agreements 4,165 1 Total identifiable intangible assets $ 1,838,065
Business Acquisition, Pro Forma Information	Three Months Ended Nine Months Ended (In thousands) September 30, September 30, September 30, September 30, Pro forma net sales $ 4,111,716 $ 4,332,980 $ 11,802,538 $ 12,758,461 Pro forma net income attributable to common stockholders 63,844 66,416 106,858 164,424 On August 6, 2020, the Company entered into a Consent Agreement with the Competition Bureau of Canada regarding the merger with Anixter. Under the Consent Agreement, the Company is required to divest its legacy Utility and Datacom businesses in Canada, which had total sales of less than $150 million in 2019. The process to divest the businesses has commenced, and WESCO is working to complete the divestitures on a timely basis. The Company expects to use the net proceeds from the divestiture to repay indebtedness.
Schedule of Business Acquisitions, by Acquisition	The following table sets forth the consideration paid for the acquisition of SLS: Nine Months Ended September 30 2019 (In thousands) Fair value of assets acquired $ 34,812 Fair value of liabilities assumed 7,070 Cash paid for acquisition $ 27,742

GOODWILL (Tables)

GOODWILL (Tables)	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020
Goodwill [Line Items]
Schedule of Goodwill [Table Text Block]	Nine Months Ended September 30 2020 EES CSS UBS Total (In thousands) Beginning balance January 1 $ 573,447 $ 235,711 $ 949,882 $ 1,759,040 Adjustments to goodwill for acquisitions (Note 4) (1) (2) 245,624 858,022 262,544 1,366,190 Foreign currency exchange rate changes (9,137) 323 2,402 (6,412) Ending balance September 30 $ 809,934 $ 1,094,056 $ 1,214,828 $ 3,118,818
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense		The following table sets forth the remaining estimated amortization expense for intangible assets for the next five years and thereafter: For year ending December 31, (In thousands) 2020 $ 26,960 2021 100,459 2022 96,608 2023 95,288 2024 91,870 Thereafter 834,758
Schedule of Finite-Lived Intangible Assets		The components of intangible assets are as follows: September 30, 2020 December 31, 2019 (In thousands) Gross Carrying Amount (1) Accumulated Amortization (1) Net Carrying Amount Gross Carrying Amount (1) Accumulated Amortization (1) Net Carrying Amount Intangible assets: Life Trademarks Indefinite $ 832,525 $ — $ 832,525 $ 98,699 $ — $ 98,699 Trademarks 10 - 15 24,894 (10,961) 13,933 24,800 (9,319) 15,481 Non-compete agreements 2 - 5 4,342 (694) 3,648 196 (180) 16 Customer relationships 10 - 20 1,455,003 (237,896) 1,217,107 358,341 (201,962) 156,379 Distribution agreements 10 - 19 37,281 (27,031) 10,250 37,371 (25,294) 12,077 Patents 10 48,310 (47,305) 1,005 48,310 (43,687) 4,623 $ 2,402,355 $ (323,887) $ 2,078,468 $ 567,717 $ (280,442) $ 287,275

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	9 Months Ended
	Sep. 30, 2020
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) 2020 2019 2020 2019 Net income attributable to WESCO International $ 80,678 $ 64,495 $ 80,578 $ 170,329 Less: Preferred stock dividends 14,511 — 15,787 — Net income attributable to common stockholders $ 66,167 $ 64,495 $ 64,791 $ 170,329 Weighted-average common shares outstanding used in computing basic earnings per share 50,043 42,100 44,873 43,545 Common shares issuable upon exercise of dilutive equity awards 444 278 231 355 Weighted-average common shares outstanding and common share equivalents used in computing diluted earnings per share 50,487 42,378 45,104 43,900 Earnings per share attributable to common stockholders Basic $ 1.32 $ 1.53 $ 1.44 $ 3.91 Diluted $ 1.31 $ 1.52 $ 1.44 $ 3.88

DEBT (Tables)

DEBT (Tables)	9 Months Ended
	Sep. 30, 2020
Debt Disclosure [Abstract]
Schedule of Debt	The following table sets forth WESCO's outstanding indebtedness: As of September 30, December 31, (In thousands) International lines of credit $ 29,787 $ 26,255 Accounts Receivable Securitization Facility 890,000 415,000 Revolving Credit Facility 325,000 — 5.375% Senior Notes due 2021 500,000 500,000 5.50% Senior Notes due 2023 58,636 — 5.375% Senior Notes due 2024 350,000 350,000 6.00% Senior Notes due 2025 4,173 — 7.125% Senior Notes due 2025 1,500,000 — 7.250% Senior Notes due 2028, less debt discount of $9,643 1,315,357 — Finance lease obligations 14,891 1,373 Total debt 4,987,844 1,292,628 Plus: Fair value adjustment to the Anixter Senior Notes 1,824 — Less: Unamortized debt issuance costs (82,700) (8,876) Less: Short-term debt and current portion of long-term debt (28,844) (26,685) Total long-term debt $ 4,878,124 $ 1,257,067

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	9 Months Ended
	Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]	During the three and nine months ended September 30, 2020 and 2019, WESCO granted the following stock-settled stock appreciation rights, restricted stock units and performance-based awards at the following weighted-average fair values: Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, Stock-settled stock appreciation rights granted — — 262,091 213,618 Weighted-average fair value $ — $ — $ 13.86 $ 16.36 Restricted stock units granted 444,375 6,256 655,825 181,800 Weighted-average fair value $ 32.18 $ 47.95 $ 37.38 $ 54.41 Performance-based awards granted — — 158,756 126,874 Weighted-average fair value $ — $ — $ 48.67 $ 54.64
Share-based Payment Arrangement, Option and Stock Appreciation Rights, 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, 2020: Awards Weighted- Weighted- Aggregate Outstanding at December 31, 2019 2,337,049 $ 59.72 Granted 262,091 48.32 Exercised (182,487) 33.57 Forfeited (39,112) 65.57 Outstanding at September 30, 2020 2,377,541 60.37 5.7 $ 679 Exercisable at September 30, 2020 1,844,929 $ 62.32 5.0 $ 679
Share-based Payment Arrangement, Restricted Stock and Restricted Stock Unit, 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, 2020: Awards Weighted- Unvested at December 31, 2019 363,729 $ 60.00 Granted 655,825 37.38 Vested (80,486) 69.68 Forfeited (8,364) 60.03 Unvested at September 30, 2020 930,704 $ 43.23
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, 2020: Awards Weighted- Unvested at December 31, 2019 195,305 $ 60.24 Granted 158,756 48.67 Vested (25,909) 78.04 Forfeited (20,538) 71.47 Unvested at September 30, 2020 307,614 $ 52.60
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]	The fair value of stock-settled stock appreciation rights was estimated using the following weighted-average assumptions: Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, Risk free interest rate n/a n/a 1.4 % 2.5 % Expected life (in years) n/a n/a 5 5 Expected volatility n/a n/a 30 % 29 %

EMPLOYEE BENEFIT PLANS Schedule

EMPLOYEE BENEFIT PLANS Schedule of Net Benefit Costs (Tables)	9 Months Ended
	Sep. 30, 2020
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 Company's defined benefit plans: Three Months Ended Nine Months Ended September 30 September 30 (In thousands) 2020 2019 2020 2019 Service cost $ 3,826 $ 1,158 $ 6,801 $ 3,446 Interest cost 4,844 1,098 7,170 3,267 Expected return on plan assets (8,399) (1,433) (12,001) (4,265) Recognized actuarial gain (1) (1) (16) 52 (47) Net periodic benefit cost $ 270 $ 807 $ 2,022 $ 2,401

Segment Reporting (Tables)

Segment Reporting (Tables)	9 Months Ended
	Sep. 30, 2020
Segment Reporting [Abstract]
Reconciliation of Assets from Segment to Consolidated	The following table sets forth total assets by reportable segment for the periods presented: As of September 30, 2020 (In thousands) EES CSS UBS Corporate (1) Total Total assets $ 3,838,242 $ 4,592,463 $ 2,990,621 $ 447,013 $ 11,868,339 As of December 31, 2019 (In thousands) EES CSS UBS Corporate (1) Total Total assets $ 2,523,481 $ 610,046 $ 1,747,809 $ 136,299 $ 5,017,635
Schedule of Segment Reporting Information, by Segment	The following table sets forth net sales and income from operations by reportable segment for the periods presented: (In thousands) Three Months Ended September 30, 2020 EES CSS UBS Corporate Total Net sales $ 1,653,726 $ 1,388,791 $ 1,099,284 $ — $ 4,141,801 Income from operations 105,508 89,634 74,092 (91,139) 178,095 Three Months Ended September 30, 2019 (In thousands) EES CSS UBS Corporate Total Net sales $ 1,250,080 $ 235,920 $ 662,110 $ — $ 2,148,110 Income from operations 72,007 10,555 43,811 (32,640) 93,733 Nine Months Ended September 30, 2020 (In thousands) EES CSS UBS Corporate Total Net sales $ 3,811,498 $ 1,953,967 $ 2,431,689 $ — $ 8,197,154 Income from operations 194,643 127,502 167,651 (235,518) 254,278 Nine Months Ended September 30, 2019 (In thousands) EES CSS UBS Corporate Total Net sales $ 3,626,423 $ 681,087 $ 1,951,955 $ — $ 6,259,465 Income from operations 198,774 32,501 134,431 (103,297) 262,409

ACCOUNTING POLICIES (Details)

ACCOUNTING POLICIES (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Prepaid expenses and other current assets	$ 166,044			$ 92,447
Assets, Current	5,597,450			2,540,411
Goodwill	3,118,818			1,759,040
Liabilities and Equity	11,868,339			5,017,635
Other Accrued Liabilities, Current	534,544			177,388
Liabilities, Current	2,540,935			1,084,059
Assets	11,868,339			5,017,635
Liabilities	8,655,115			2,758,964
Retained earnings	2,596,022	$ 2,529,842	$ 2,565,597	2,530,429	$ 2,477,259	$ 2,412,768	$ 2,349,300	$ 2,307,462
Accumulated other comprehensive income	(377,461)	$ (418,889)	$ (461,623)	(367,772)	$ (382,530)	$ (365,674)	$ (385,918)	$ (408,435)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 3,213,224			$ 2,258,671

REVENUE (Details)

REVENUE (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Deferred Revenue	$ 27,700		$ 27,700		$ 12,300
Revenue from Contract with Customer, Excluding Assessed Tax	4,141,801	$ 2,148,110	8,197,154	$ 6,259,465
Cost of goods sold	$ 3,356,259	$ 1,747,913	$ 6,641,438	$ 5,067,799
Revenue, Information Used to Assess Variable Consideration Constraint	75.4 million	26.3 million	129.0 million	80.1 million
EES
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 1,653,726	$ 1,250,080	$ 3,811,498	$ 3,626,423
CSS
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,388,791	235,920	1,953,967	681,087
UBS
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,099,284	662,110	2,431,689	1,951,955
UNITED STATES
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3,033,101	1,601,962	6,100,877	4,679,251
CANADA
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	582,700	431,233	1,311,724	1,230,855
Non-US [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	526,000	114,915	784,553	349,359
Shipping and Handling [Member]
Disaggregation of Revenue [Line Items]
Cost of goods sold	$ 55,500	$ 17,600	$ 94,400	$ 52,800

REVENUE Deferred Revenue (Detai

REVENUE Deferred Revenue (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Deferred Revenue	$ 27.7	$ 12.3

REVENUE Shipping and Handling C

REVENUE Shipping and Handling Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Cost of goods sold	$ 3,356,259	$ 1,747,913	$ 6,641,438	$ 5,067,799
Shipping and Handling [Member]
Cost of goods sold	$ 55,500	$ 17,600	$ 94,400	$ 52,800

REVENUE Variable Consideration

REVENUE Variable Consideration (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue, Methods, Inputs, and Assumptions Used [Abstract]
Revenue, Information Used to Assess Variable Consideration Constraint	75.4 million	26.3 million	129.0 million	80.1 million

REVENUE Revenue, Performance Ob

REVENUE Revenue, Performance Obligation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue from Contract with Customer [Abstract]
Cost of goods sold	$ 3,356,259	$ 1,747,913	$ 6,641,438	$ 5,067,799

SCHEDULE OF CONSIDERATION TRANS

SCHEDULE OF CONSIDERATION TRANSFERRED (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	$ 3,707,575	$ 27,742
Anixter International
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	3,811,038
Fair value of cash consideration	2,563,385
Equity consideration	887,298
Payment for Debt Extinguishment	1,247,653
Total purchase consideration	4,698,336
Cash acquired	(103,463)
Cash paid for acquisition	3,707,575
Anixter International | Common Stock [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	2,476,010
Equity consideration	313,512
Anixter International | Preferred Stock
Business Acquisition [Line Items]
Equity consideration	573,786
Anixter International | Restricted Stock
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	$ 87,375
Sylvania Lighting Services Corp. [Member]
Business Acquisition [Line Items]
Cash paid for acquisition		$ 27,742

SCHEDULE OF ASSETS AND LIABILIT

SCHEDULE OF ASSETS AND LIABILITIES - ANIXTER (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Jun. 22, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Goodwill	$ 3,118,818		$ 1,759,040
Anixter International
Business Acquisition [Line Items]
Cash and cash equivalents		$ 103,463
Trade accounts receivable		1,309,104
Other accounts receivable		116,386
Inventories		1,424,678
Prepaid expenses and other current assets		53,462
Property, buildings and equipment		213,020
Operating lease assets		262,413
Intangible assets		1,838,065
Goodwill		1,360,373
Other assets		112,386
Total assets		6,793,350
Accounts payable		920,163
Accrued payroll and benefit costs		69,480
Short-term debt and current portion of long-term debt		13,225
Other current liabilities		222,615
Long-term debt		77,822
Operating lease liabilities		199,959
Deferred income taxes		384,890
Other noncurrent liabilities		206,860
Total liabilities		2,095,014
Fair value of net assets acquired, including goodwill and intangible assets		$ 4,698,336

SCHEDULE OF IDENTIFIABLE INTANG

SCHEDULE OF IDENTIFIABLE INTANGIBLE ASSETS (Details) - Anixter International - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Jun. 22, 2020
Business Acquisition [Line Items]
Intangible assets		$ 1,838,065
Trademarks [Member]
Business Acquisition [Line Items]
Acquired Indefinite-Lived Intangible Assets		735,000
Customer Relationships [Member]
Business Acquisition [Line Items]
Acquired Finite-Lived Intangibles		1,098,900
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	16 years
Noncompete Agreements [Member]
Business Acquisition [Line Items]
Acquired Finite-Lived Intangibles		$ 4,165
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	1 year

SCHEDULE OF PRO FORMA INFORMATI

SCHEDULE OF PRO FORMA INFORMATION (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Anixter International
Business Acquisition [Line Items]
Pro forma net sales	$ 4,111,716	$ 4,332,980	$ 11,802,538	$ 12,758,461
Pro forma net income attributable to common stockholders	63,844	$ 66,416	106,858	$ 164,424
Business Combination, Acquisition Related Costs	$ 14,500		$ 92,100
Anixter International acquisition [Member]
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Information, Description			The following unaudited pro forma financial information presents combined results of operations for the periods presented, as if the Company had completed the Merger on January 1, 2019. The unaudited pro forma financial information includes adjustments to amortization and depreciation for intangible assets and property, buildings and equipment, adjustments to interest expense for the additional indebtedness incurred to complete the acquisition (including the amortization of debt discount and issuance costs), transaction costs, change in control and severance costs, dividends accrued on the Series A preferred stock, compensation expense associated with the WESCO phantom stock unit awards described in Note 10, as well as the respective income tax effects of such adjustments. For the three months ended September 30, 2020 and 2019, adjustments totaling $1.5 million and $57.4 million, respectively, decreased the unaudited pro forma net income attributable to common stockholders. For the nine months ended September 30, 2020 and 2019, adjustments totaling $0.4 million and $167.8 million, respectively, decreased the unaudited pro forma net income attributable to common stockholders. The unaudited pro forma financial information does not reflect any cost savings, operating synergies or revenue enhancements that WESCO may achieve as a result of its acquisition of Anixter, the costs to integrate the operations of WESCO and Anixter or the costs necessary to achieve these cost savings, operating synergies and revenue enhancements. The unaudited pro forma financial information presented below is not necessarily indicative of consolidated results of operations of the combined business had the acquisition occurred at the beginning of the respective fiscal years, nor is it necessarily indicative of future results of operations of the combined company.

SCHEDULE OF ACQUISITIONS - SYLV

SCHEDULE OF ACQUISITIONS - SYLVANIA (Details) - Sylvania Lighting Services Corp. [Member] $ in Thousands	9 Months Ended
	Sep. 30, 2019USD ($)
Business Acquisition [Line Items]
Fair value of assets acquired	$ 34,812
Fair value of liabilities assumed	7,070
Cash paid for acquisition	$ 27,742

ACQUISITIONS (Details)

ACQUISITIONS (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2020USD ($)numberOfEmployeescountriesnumberOfCities	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)numberOfEmployeescountriesnumberOfCities	Sep. 30, 2019USD ($)	Jun. 22, 2020USD ($)$ / sharesshares
Business Acquisition [Line Items]
Number of Cities in which an Entity Operates | numberOfCities	300		300
Revenue from Contract with Customer, Excluding Assessed Tax	$ 4,141,801,000	$ 2,148,110,000	$ 8,197,154,000	$ 6,259,465,000
Operating Income (Loss)	178,095,000	93,733,000	254,278,000	262,409,000
Revenues	$ 4,141,801,000	2,148,110,000	$ 8,197,154,000	6,259,465,000
Business Combination, Provisional Information, Initial Accounting Incomplete, Reasons			The estimated fair values of assets acquired and liabilities assumed are based on preliminary calculations and valuations using estimates and assumptions at the time of acquisition. The determination of the fair values of assets acquired and liabilities assumed, especially those related to identifiable intangible assets, is preliminary due to the complexity of combining multibillion dollar businesses. Accordingly, as the Company obtains additional information during the measurement period (not to exceed one year from the acquisition date), estimates and assumptions for the preliminary purchase consideration allocations may change materially.
Business Combination, Reason for Business Combination			The Merger brought together two companies with highly compatible capabilities and characteristics. The combination of WESCO and Anixter created an enterprise with scale and should afford the Company the opportunity to digitize its business, and expand its services portfolio and supply chain offerings.
Business Acquisition, Description of Acquired Entity			Anixter is a leading distributor of network and security solutions, electrical and electronic solutions, and utility power solutions with locations in over 300 cities across approximately 50 countries, and 2019 annual sales of more than $8 billion.
Business Combination, Goodwill Recognized, Description			The resulting goodwill is primarily attributable to Anixter's workforce, significant cross-selling opportunities in additional geographies, enhanced scale, and other operational efficiencies.In the third quarter of 2020, the Company recognized adjustments to total identifiable intangible assets and deferred income taxes of $5.4 million and $7.3 million, respectively. Certain other measurement period adjustments were made to the identified assets acquired and liabilities assumed, none of which were significant, individually or in aggregate. The net impact of the adjustments made in the third quarter of 2020 was a decrease to goodwill of $7.6 million.
Anixter International
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition			Jun. 22, 2020
Common stock, shares, issued (in shares) | shares					0.2397
Common stock					$ 0.01
Preferred stock, shares issued (in shares) | shares					0.6356
Preferred stock, par value (in dollars per share) | $ / shares					$ 25,000
Preferred Stock, Dividend Rate, Percentage			10.625%
Additional countries (in countries) | countries	50		50
Business Acquisition, Revenue Reported by Acquired Entity for Last Annual Period			$ 8,000,000,000
Operating Income (Loss)	$ 80,000,000		98,400,000
Revenues	2,200,000,000		2,400,000,000
Business Combination, Acquisition Related Costs	$ 14,500,000		$ 92,100,000
Anixter International | Cash [Member]
Business Acquisition [Line Items]
Business Acquisition, Share Price | $ / shares					$ 72.82
Sylvania Lighting Services Corp. [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition			Mar. 5, 2019
Business Acquisition, Revenue Reported by Acquired Entity for Last Annual Period			$ 100,000,000
Number of Employees Employed by the Entity | numberOfEmployees	220		220
Business Acquisition, Goodwill, Expected Tax Deductible Amount		$ 11,600,000		$ 11,600,000

GOODWILL (Details)

GOODWILL (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Goodwill [Line Items]
Goodwill	$ 3,118,818		$ 3,118,818		$ 1,759,040
Goodwill, Foreign Currency Translation Gain (Loss)			(6,412)
Goodwill, Acquired During Period			1,366,190
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	2,402,355		2,402,355		567,717
Finite-Lived Intangible Assets, Accumulated Amortization	(323,887)		(323,887)		(280,442)
Finite-Lived Intangible Assets, Net	2,078,468		2,078,468		287,275
Finite-Lived Intangible Asset, Expected Amortization, Year One	26,960		26,960
Finite-Lived Intangible Asset, Expected Amortization, Year Two	100,459		100,459
Finite-Lived Intangible Asset, Expected Amortization, Year Three	96,608		96,608
Finite-Lived Intangible Asset, Expected Amortization, Year Four	95,288		95,288
Finite-Lived Intangible Asset, Expected Amortization, Year Five	91,870		91,870
Finite-Lived Intangible Asset, Expected Amortization, after Year Five	834,758		834,758
Amortization of Intangible Assets	27,300	$ 8,600	45,900	$ 25,700
Finite-Lived Intangible Asset, Expected Amortization, Year Three	96,608		96,608
Finite-Lived Intangible Asset, Expected Amortization, Year Four	95,288		95,288
Finite-Lived Intangible Asset, Expected Amortization, Year Five	91,870		91,870
Finite-Lived Intangible Asset, Expected Amortization, after Year Five	834,758		834,758
Trademarks [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	24,894		24,894		24,800
Finite-Lived Intangible Assets, Accumulated Amortization	(10,961)		(10,961)		(9,319)
Finite-Lived Intangible Assets, Net	13,933		$ 13,933		15,481
Trademarks [Member] | Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life			10 years
Trademarks [Member] | Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life			15 years
Noncompete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	4,342		$ 4,342		196
Finite-Lived Intangible Assets, Accumulated Amortization	(694)		(694)		(180)
Finite-Lived Intangible Assets, Net	3,648		$ 3,648		16
Noncompete Agreements [Member] | Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life			2 years
Noncompete Agreements [Member] | Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life			5 years
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	1,455,003		$ 1,455,003		358,341
Finite-Lived Intangible Assets, Accumulated Amortization	(237,896)		(237,896)		(201,962)
Finite-Lived Intangible Assets, Net	1,217,107		$ 1,217,107		156,379
Customer Relationships [Member] | Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life			10 years
Customer Relationships [Member] | Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life			20 years
Distribution Rights [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	37,281		$ 37,281		37,371
Finite-Lived Intangible Assets, Accumulated Amortization	(27,031)		(27,031)		(25,294)
Finite-Lived Intangible Assets, Net	10,250		$ 10,250		12,077
Distribution Rights [Member] | Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life			10 years
Distribution Rights [Member] | Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life			19 years
Patents [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life			10 years
Finite-Lived Intangible Assets, Gross	48,310		$ 48,310		48,310
Finite-Lived Intangible Assets, Accumulated Amortization	(47,305)		(47,305)		(43,687)
Finite-Lived Intangible Assets, Net	1,005		1,005		4,623
EES
Goodwill [Line Items]
Goodwill	809,934		809,934		573,447
Goodwill, Foreign Currency Translation Gain (Loss)			(9,137)
Goodwill, Acquired During Period			245,624
CSS
Goodwill [Line Items]
Goodwill	1,094,056		1,094,056		235,711
Goodwill, Foreign Currency Translation Gain (Loss)			858,022
Goodwill, Acquired During Period			323
UBS
Goodwill [Line Items]
Goodwill	1,214,828		1,214,828		949,882
Goodwill, Foreign Currency Translation Gain (Loss)			262,544
Goodwill, Acquired During Period			2,402
Trademarks [Member]
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived Intangible Assets (Excluding Goodwill)	$ 832,525		$ 832,525		$ 98,699

SCHEDULE OF EARNINGS PER SHARE,

SCHEDULE OF EARNINGS PER SHARE, BASIC AND DILUTED (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share [Abstract]
Net income (loss) attributable to WESCO International, Inc.	$ 80,678	$ (34,506)	$ 34,407	$ 64,495	$ 63,464	$ 42,369	$ 80,578	$ 170,329
Weighted average common shares outstanding used in computing basic earnings per share (in shares)	50,043,000			42,100,000			44,873,000	43,545,000
Common shares issuable upon exercise of dilutive stock options (in shares)	444,000			278,000			231,000	355,000
Weighted average common shares outstanding and common share equivalents used in computing diluted earnings per share (in shares)	50,487,000			42,378,000			45,104,000	43,900,000
Earnings Per Share, Basic and Diluted [Abstract]
Basic (in dollars per share)	$ 1.32			$ 1.53			$ 1.44	$ 3.91
Diluted (in dollars per share)	$ 1.31			$ 1.52			$ 1.44	$ 3.88
Net Income (Loss) Available to Common Stockholders, Basic	$ 66,167			$ 64,495			$ 64,791	$ 170,329

EARNINGS PER SHARE (Details)

EARNINGS PER SHARE (Details) - shares	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2019
Award Type [Domain]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	2,000,000	3,000,000	1,800,000

EARNINGS PER SHARE Accelerated

EARNINGS PER SHARE Accelerated Share Repurchase (Details) - USD ($) $ in Thousands	3 Months Ended				4 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Mar. 07, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Accelerated Share Repurchases [Line Items]
Payments for Repurchase of Common Stock						$ (2,032)	$ (152,735)
Stock Repurchase Program, Authorized Amount								$ 400,000	$ 300,000
Treasury Stock, Shares, Acquired		695,496	2,394,816	365,272	365,272		3,455,584
Stock Repurchase Program Expiration Date	Dec. 31, 2020

SCHEDULE OF DEBT (Details)

SCHEDULE OF DEBT (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Finance lease obligations	$ 14,891	$ 1,373
Total debt	4,987,844	1,292,628
Fair value adjustment to the Anixter Notes	1,824	0
Unamortized debt issuance costs	(82,700)	(8,876)
Short-term debt and current portion of long-term debt	(28,844)	(26,685)
Total long-term debt	4,878,124	1,257,067
Foreign Line of Credit
Debt Instrument [Line Items]
Long-term Debt	29,787	26,255
Accounts Receivable Securitization Facility
Debt Instrument [Line Items]
Long-term Debt	890,000	415,000
Revolving Credit Facility
Debt Instrument [Line Items]
Long-term Debt	325,000	0
5.375% Senior Notes due 2021
Debt Instrument [Line Items]
Long-term Debt	500,000	500,000
5.50% Senior Notes due 2023
Debt Instrument [Line Items]
Long-term Debt	58,636	0
5.375% Senior Notes due 2024
Debt Instrument [Line Items]
Long-term Debt	350,000	350,000
6.00% Senior Notes due 2025
Debt Instrument [Line Items]
Long-term Debt	4,173	0
7.125% Senior Notes due 2025
Debt Instrument [Line Items]
Long-term Debt	1,500,000	0
7.250% Senior Notes due 2028
Debt Instrument [Line Items]
Long-term Debt	1,315,357	$ 0
Debt Instrument, Unamortized Discount	$ 9,643

DEBT (Details)

DEBT (Details) - USD ($)	3 Months Ended	9 Months Ended
	Mar. 31, 2020	Sep. 30, 2020	Jun. 23, 2020	Dec. 31, 2019
Accounts Receivable Securitization Facility
Debt Instrument [Line Items]
Debt Instrument, Issuance Date		Jun. 22, 2020
Line of Credit Facility, Maximum Borrowing Capacity		$ 1,025,000,000		$ 600,000,000
Line of Credit Facility, Opportunity to Increase Borrowing Capacity		$ 375,000,000
Debt Instrument, Maturity Date		Jun. 22, 2023
Debt Instrument, Basis Spread on Variable Rate	0.95%	1.20%
Line of Credit Facility, Commitment Fee Percentage		0.45%
Accounts Receivable Securitization Facility | Interest Rate Floor [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		0.50%
Revolving Credit Facility
Debt Instrument [Line Items]
Debt Instrument, Issuance Date		Jun. 22, 2020
Line of Credit Facility, Maximum Borrowing Capacity		$ 1,100,000,000
Line of Credit Facility, Opportunity to Increase Borrowing Capacity		500,000,000
Revolving Credit Facility | Letter of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 175,000,000
5.50% Senior Notes due 2023
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.50%
Debt Instrument, Face Amount		$ 350,000,000
Senior Notes tender offer consideration per $1,000 principal amount			$ 1,012.50
Senior Notes early tender payment per $1,000 principal amount			50
Senior Notes consent fee per $1,000 principal amount			2.50
Senior Notes		$ 58,600,000
6.00% Senior Notes due 2025
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.00%
Debt Instrument, Face Amount		$ 250,000,000
Senior Notes tender offer consideration per $1,000 principal amount			1,012.50
Senior Notes early tender payment per $1,000 principal amount			50
Senior Notes consent fee per $1,000 principal amount			$ 2.50
Senior Notes		$ 4,200,000
7.125% Senior Notes due 2025
Debt Instrument [Line Items]
Debt Instrument, Issuance Date		Jun. 12, 2020
Debt Instrument, Maturity Date		Jun. 15, 2025
Debt Instrument, Interest Rate, Stated Percentage		7.125%
Debt Instrument, Face Amount		$ 1,500,000,000
Discount percentage of par value		100.00%
Debt Instrument, Redemption Price, Percentage		35.00%
Percentage of principal amount of Senior Notes accelerated under default		25.00%
7.250% Senior Notes due 2028
Debt Instrument [Line Items]
Debt Instrument, Issuance Date		Jun. 12, 2020
Debt Instrument, Maturity Date		Jun. 15, 2028
Debt Instrument, Interest Rate, Stated Percentage		7.25%
Debt Instrument, Face Amount		$ 1,325,000,000
Discount percentage of par value		99.244%
Debt Instrument, Redemption Price, Percentage		35.00%
Percentage of principal amount of Senior Notes accelerated under default		25.00%
Minimum [Member] | Revolving Credit Facility | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.25%
Minimum [Member] | Revolving Credit Facility | Prime Rate [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		0.25%
Maximum [Member] | Revolving Credit Facility | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.50%
Maximum [Member] | Revolving Credit Facility | Prime Rate [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		0.50%

SCHEDULE OF SHARE-BASED COMPENS

SCHEDULE OF SHARE-BASED COMPENSATION, STOCK OPTIONS AND STOCK APPRECIATION RIGHTS AWARD ACTIVITY (Details) - Stock Appreciation Rights (SARs) [Member] - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Share-based Compensation Arrangement By Share-based Payment Award, Options and Stock Appreciation Rights, Outstanding [Roll Forward]
Grants in Period (in shares)	0	0	262,091	213,618
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value			$ 48.32
Exercises in Period (in shares)			182,487
Weighted Average Exercise Price, Exercises in Period (in dollars per share)			$ 33.57
Forfeitures in Period (in shares)			39,112
Weighted Average Exercise Price, Forfeitures in Period (in dollars per share)			$ 65.57
Weighted Average Remaining Contractual Term, Outstanding (in years)			5 years 8 months 12 days
Weighted Average Remaining Contractual Term, Exercisable (in years)			5 years
Aggregate Intrinsic Value, Outstanding	$ 679		$ 679
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	$ 679		$ 679
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number	2,377,541		2,377,541		2,337,049
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$ 60.37		$ 60.37		$ 59.72
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Number	1,844,929		1,844,929
Weighted Average Exercise Price, Exercisable (in dollars per share)	$ 62.32		$ 62.32

SCHEDULE OF SHARE-BASED PAYMENT

SCHEDULE OF SHARE-BASED PAYMENT AWARD, VALUATION ASSUMPTIONS (Details) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate			1.40%	2.50%
Expected life (in years)			5 years	5 years
WESCO expected volatility			30.00%	29.00%
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	0	0	262,091	213,618
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	$ 13.86	$ 16.36
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	444,375	6,256	655,825	181,800
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 32.18	$ 47.95	$ 37.38	$ 54.41
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	0	0	158,756	126,874
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	$ 48.67	$ 54.64

SUMMARY OF RESTRICTED STOCK UNI

SUMMARY OF RESTRICTED STOCK UNITS (Details) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Unvested (in shares)	930,704		930,704		363,729
Granted (in shares)	444,375	6,256	655,825	181,800
Vested (in shares)			(80,486)
Forfeited (in shares)			(8,364)
Unvested, Weighted Average Fair Value (in dollars per share)	$ 43.23		$ 43.23		$ 60
Granted, Weighted Average Fair Value (in dollars per share)	$ 32.18	$ 47.95	37.38	$ 54.41
Vested in Period, Weighted Average Fair Value (in dollars per share)			69.68
Forfeited in Period, Weighted Average Fair Value (in dollars per share)			$ 60.03
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Unvested (in shares)	307,614		307,614		195,305
Granted (in shares)	0	0	158,756	126,874
Vested (in shares)			(25,909)
Forfeited (in shares)			(20,538)
Unvested, Weighted Average Fair Value (in dollars per share)	$ 52.60		$ 52.60		$ 60.24
Granted, Weighted Average Fair Value (in dollars per share)	$ 0	$ 0	48.67	$ 54.64
Vested in Period, Weighted Average Fair Value (in dollars per share)			78.04
Forfeited in Period, Weighted Average Fair Value (in dollars per share)			$ 71.47

SUMMARY OF PERFORMANCE-BASED AW

SUMMARY OF PERFORMANCE-BASED AWARDS (Details) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Unvested (in shares)	307,614		307,614		195,305
Granted (in shares)	0	0	158,756	126,874
Vested (in shares)			(25,909)
Forfeited (in shares)			(20,538)
Unvested, Weighted Average Fair Value (in dollars per share)	$ 52.60		$ 52.60		$ 60.24
Granted, Weighted Average Fair Value (in dollars per share)	$ 0	$ 0	48.67	$ 54.64
Vested in Period, Weighted Average Fair Value (in dollars per share)			78.04
Forfeited in Period, Weighted Average Fair Value (in dollars per share)			$ 71.47
Share-based Payment Arrangement, Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Unvested (in shares)	307,614		307,614
Share-based Payment Arrangement, 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)	134,010		134,010
Share-based Payment Arrangement, 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)	153,807		153,807
Share-based Payment Arrangement, 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 PAYME_2

SCHEDULE OF SHARE-BASED PAYMENT AWARD, PERFORMANCE-BASED AWARDS, VALUATION ASSUMPTIONS (Details)	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
WESCO expected volatility	30.00%	29.00%
Risk free interest rate	1.40%	2.50%

STOCK-BASED COMPENSATION (Detai

STOCK-BASED COMPENSATION (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2021	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense					$ 6	$ 4.4	$ 15.5	$ 14.2
Total unrecognized compensation cost					$ 39.8		$ 39.8
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)					307,614		307,614
Forecast [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 3.6	$ 12.4	$ 17.8	$ 6

Equity (Details)

Equity (Details) - $ / shares	Jun. 22, 2025	Sep. 30, 2020	Jun. 30, 2020	Jun. 22, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Series A Preferred Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Preferred stock, shares authorized (in shares)		25,000
Preferred Stock, Dividend Rate, Percentage		10.625%
Preferred stock, par value (in dollars per share)		$ 0.01
Preferred Stock, Dividend Payment Rate, Variable	10.325
Preferred Stock, Liquidation Preference Per Share		$ 25,000
Preferred stock, shares issued (in shares)		21,612	21,612	21,612	0	0	0	0	0	0
Depositary Share [Member]
Equity, Class of Treasury Stock [Line Items]
Preferred stock, shares issued (in shares)				21,611,534

EMPLOYEE BENEFIT PLANS EMPLOYEE

EMPLOYEE BENEFIT PLANS EMPLOYEE BENEFIT PLANS Pension Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Defined Contribution Plan Disclosure [Line Items]
Assets Held-in-trust	$ 39,500		$ 39,500
Defined Benefit Plan, Plan Assets, Contributions by Employer	2,900		4,700
Postemployment Benefits, Period Expense			13,600	$ 24,700
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	3,826	$ 1,158	6,801	3,446
Interest cost	4,844	1,098	7,170	3,267
Expected return on plan assets	8,399	1,433	12,001	4,265
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	1	16	(52)	47
Net periodic benefit cost	270	807	2,022	2,401
Defined Benefit Plan, Service Cost	3,826	1,158	6,801	3,446
Defined Benefit Plan, Plan Assets, Contributions by Employer	2,900		4,700
Postemployment Benefits, Period Expense			13,600	24,700
Anixter International
Defined Contribution Plan Disclosure [Line Items]
Deferred Compensation Liability, Current	3,800		3,800
Deferred Compensation Liability, Classified, Noncurrent	42,400		42,400
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Deferred Compensation Liability, Current	3,800		3,800
WESCO
Defined Contribution Plan Disclosure [Line Items]
Deferred Compensation Liability, Current	10,100		10,100
Deferred Compensation Liability, Classified, Noncurrent	15,900		15,900		$ 25,200
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Deferred Compensation Liability, Current	10,100		10,100
Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Other Nonoperating Gains (Losses)	(3,600)	$ (400)	$ (4,800)	$ (1,000)
Canadian 401K Defined Contribution Plan [Member] | Minimum [Member]
Defined Contribution Plan Disclosure [Line Items]
Defined Contribution Plan Employer Matching Contribution Percent			3.00%
Canadian 401K Defined Contribution Plan [Member] | Maximum [Member]
Defined Contribution Plan Disclosure [Line Items]
Defined Contribution Plan Employer Matching Contribution Percent			5.00%
US 401K Defined Contribution Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Matching Contribution, Percent of Match			50.00%
Defined Contribution Plan Employer Matching Contribution Percent			6.00%
Anixter Employee Savings Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Matching Contribution, Percent of Match			50.00%
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent			5.00%
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent			5.00%
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent			5.00%
Anixter Employee Savings Plan [Member] | Minimum [Member]
Defined Contribution Plan Disclosure [Line Items]
Defined Contribution Plan Employer Matching Contribution Percent			2.00%
Anixter Employee Savings Plan [Member] | Maximum [Member]
Defined Contribution Plan Disclosure [Line Items]
Defined Contribution Plan Employer Matching Contribution Percent			2.50%
Phantom Share Units (PSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period			3 years
Share-based Payment Arrangement, Expense	1,400		$ 2,300
Other Deferred Compensation Arrangements, Liability, Classified, Noncurrent	$ 13,400		$ 13,400

FAIR VALUE (Details)

FAIR VALUE (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total debt	$ 4,987,844	$ 1,292,628
5.375% Senior Notes due 2024
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	350,000	350,000
5.375% Senior Notes due 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	500,000	500,000
Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	4,015,600	866,200
Long-term Debt	$ 3,730,000	$ 850,000

COMMITMENTS AND CONTINGENCIES_2

COMMITMENTS AND CONTINGENCIES Guarantees (Details)	3 Months Ended
	Sep. 30, 2020
Guarantees and Product Warranties [Abstract]
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 debt facilities.

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Tax Contingency [Line Items]
Effective tax rate	23.30%	19.80%	22.90%	21.00%
Tax Credit Carryforward [Line Items]
Tax Credit Carryforward, Amount	$ 59,400		$ 59,400
Tax Credit Carryforward, Valuation Allowance	$ 41,400		41,400
Anixter International acquisition [Member]
Tax Credit Carryforward [Line Items]
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount			$ 30,000

INCOME TAXES Income Tax Rates (

INCOME TAXES Income Tax Rates (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation, Percent	23.30%	19.80%	22.90%	21.00%

Segment Reporting (Details)

Segment Reporting (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Segment Reporting [Abstract]
Revenues	$ 4,141,801	$ 2,148,110	$ 8,197,154	$ 6,259,465
Operating Income (Loss)	178,095	93,733	254,278	262,409
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	4,141,801	2,148,110	8,197,154	6,259,465
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Operating Income (Loss)	178,095	93,733	254,278	262,409
Revenues	4,141,801	2,148,110	8,197,154	6,259,465
Revenue from Contract with Customer, Excluding Assessed Tax	4,141,801	2,148,110	8,197,154	6,259,465
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	11,868,339		11,868,339		$ 5,017,635
EES
Segment Reporting [Abstract]
Operating Income (Loss)	105,508	72,007	194,643	198,774
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Operating Income (Loss)	105,508	72,007	194,643	198,774
Revenue from Contract with Customer, Excluding Assessed Tax	1,653,726	1,250,080	3,811,498	3,626,423
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	3,838,242		3,838,242		2,523,481
CSS
Segment Reporting [Abstract]
Operating Income (Loss)	89,634	10,555	127,502	32,501
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Operating Income (Loss)	89,634	10,555	127,502	32,501
Revenue from Contract with Customer, Excluding Assessed Tax	1,388,791	235,920	1,953,967	681,087
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	4,592,463		4,592,463		610,046
UBS
Segment Reporting [Abstract]
Operating Income (Loss)	74,092	43,811	167,651	134,431
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Operating Income (Loss)	74,092	43,811	167,651	134,431
Revenue from Contract with Customer, Excluding Assessed Tax	1,099,284	662,110	2,431,689	1,951,955
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	2,990,621		2,990,621		1,747,809
Corporate Segment
Segment Reporting [Abstract]
Operating Income (Loss)	(91,139)	(32,640)	(235,518)	(103,297)
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Operating Income (Loss)	(91,139)	(32,640)	(235,518)	(103,297)
Revenue from Contract with Customer, Excluding Assessed Tax	0	$ 0	0	$ 0
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 447,013		$ 447,013		$ 136,299