0000929008-21-000036 | 10-Q | XBRL Viewer

COVER PAGE - shares	9 Months Ended
COVER PAGE - shares	Sep. 30, 2021	Nov. 04, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
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
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		50,409,946
Entity Registrant Name	WESCO International, Inc.
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Current Reporting Status	Yes
Entity Central Index Key	0000929008
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
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
Series A Preferred Stock [Member] \| NEW YORK STOCK EXCHANGE, INC.
Cover [Abstract]
Trading Symbol	WCC PR A
Security Exchange Name	NYSE
Entity Listings [Line Items]
Trading Symbol	WCC PR A
Security Exchange Name	NYSE
Common Class A [Member]
Cover [Abstract]
Title of 12(b) Security	Common Stock, par value $.01 per share
Entity Listings [Line Items]
Title of 12(b) Security	Common Stock, par value $.01 per share
Common Class A [Member] \| NEW YORK STOCK EXCHANGE, INC.
Cover [Abstract]
Trading Symbol	WCC
Security Exchange Name	NYSE
Entity Listings [Line Items]
Trading Symbol	WCC
Security Exchange Name	NYSE

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Cash and cash equivalents	$ 251,799	$ 449,135
Accounts Receivable, after Allowance for Credit Loss, Current	2,955,632	2,466,903
Accounts and Other Receivables, Net, Current	323,597	239,199
Inventories, net	2,569,798	2,163,831
Prepaid expenses and other current assets	114,670	187,910
Assets, Current	6,215,496	5,506,978
Property, buildings and equipment, net of accumulated depreciation of $229,041 and $213,758 in 2014 and 2013, respectively	369,815	399,157
Operating Lease, Right-of-Use Asset	540,173	534,705
Intangible assets, net	1,977,841	2,065,495
Goodwill	3,201,688	3,187,169
Other assets	176,005	131,637
Assets Held-for-sale, Not Part of Disposal Group	0	55,073
Assets	12,481,018	11,880,214
Accounts payable	2,246,454	1,707,329
Accrued payroll and benefit costs	285,362	198,535
Current portion of long-term debt	19,292	528,830
Other Liabilities, Current	586,991	552,301
Liabilities, Current	3,138,099	2,986,995
Total long-term debt	4,565,772	4,369,953
Operating Lease, Liability, Noncurrent	421,831	414,889
Deferred Income Tax Liabilities, Net	485,548	488,261
Other Liabilities, Noncurrent	287,951	278,010
Disposal Group, Including Discontinued Operation, Accounts Payable and Accrued Liabilities	0	5,717
Liabilities	8,899,201	8,543,825
Commitments and Contingencies
Additional capital	1,961,369	1,942,810
Retained earnings	$ 2,851,747	$ 2,601,662
Treasury stock, shares (in shares)	21,980,847	21,870,961
Treasury stock, at cost; 21,980,847 and 21,870,961 shares in 2021 and 2020, respectively	$ (950,004)	$ (938,335)
Accumulated other comprehensive income	(275,351)	(263,134)
Total WESCO International, Inc. stockholders' equity	3,588,485	3,343,722
Noncontrolling interest	(6,668)	(7,333)
Total stockholders’ equity	3,581,817	3,336,389
Liabilities and Equity	$ 12,481,018	$ 11,880,214
Preferred Stock
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 outstanding (in shares)	0	0
Preferred stock, shares issued (in shares)	0	0
Preferred stock, $.01 par value; 20,000,000 shares authorized, no shares issued or outstanding	$ 0	$ 0
Series A Preferred Stock [Member]
Preferred stock, par value (in dollars per share)	$ 0.01
Preferred stock, shares authorized (in shares)	25,000
Preferred stock, shares outstanding (in shares)	21,612
Preferred stock, shares issued (in shares)	21,612	21,612
Preferred stock, $.01 par value; 20,000,000 shares authorized, no shares issued or outstanding	$ 0	$ 0
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)	68,049,518	67,596,515
Common stock, shares outstanding (in shares)	50,408,102	50,064,985
Common stock	$ 681	$ 676
Common Class B [Member]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	20,000,000	20,000,000
Common stock, shares, issued (in shares)	4,339,431	4,339,431
Common stock, shares outstanding (in shares)	0	0
Common stock	$ 43	$ 43

CONSOLIDATED BALANCE SHEETS (parenthetical items) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Accounts Receivable, Allowance for Credit Loss, Current	$ 38,550	$ 23,909
Accumulated depreciation	352,586	312,106
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	$ 74,222	87,142
5.375% Senior Notes due 2021
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net		$ 1,039

CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Gross Profit [Abstract]
Revenues	$ 4,728,325	$ 4,141,801	$ 13,365,592	$ 8,197,154
Cost of goods sold	3,720,332	3,356,259	10,581,406	6,641,438
Operating Expenses [Abstract]
Selling, general and administrative expense	721,795	561,971	2,057,952	1,221,114
Depreciation and amortization	56,732	45,476	144,645	80,324
Income from operations	229,466	178,095	581,589	254,278
Nonoperating Income (Expense)	69,720	74,540	207,683	152,281
Other Nonoperating Income (Expense)	(5,320)	(777)	(8,929)	(1,463)
Income before income taxes	165,066	104,332	382,835	103,460
Provision for income taxes	44,870	24,294	84,201	23,707
Net income	120,196	80,038	298,634	79,753
Net (loss) income attributable to noncontrolling interest	600	(640)	665	(825)
Net income attributable to WESCO International, Inc.	119,596	80,678	297,969	80,578
Preferred Stock Dividends, Income Statement Impact	14,352	14,511	43,056	15,787
Net Income (Loss) Available to Common Stockholders, Basic	105,244	66,167	254,913	64,791
Comprehensive Income:
Foreign currency translation adjustment	(50,277)	41,428	(12,217)	(9,689)
Comprehensive income attributable to WESCO International, Inc.	$ 54,967	$ 107,595	$ 242,696	$ 55,102
Basic (in dollars per share)	$ 2.09	$ 1.32	$ 5.07	$ 1.44
Diluted (in dollars per share)	$ 2.02	$ 1.31	$ 4.91	$ 1.44

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Operating Activities:
Net income	$ 298,634	$ 79,753
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	144,645	80,324
Stock-based compensation expense	22,784	15,529
Amortization of Debt Issuance Costs and Discounts	15,290	6,301
Gain (Loss) on Disposition of Business	(8,927)	(19,816)
Deferred income taxes	(5,340)	(8,261)
Other operating activities, net	8,604	(3,777)
Changes in assets and liabilities
Increase (Decrease) in Accounts Receivable	521,491	(3,584)
Increase (Decrease) in Accounts and Other Receivables	(84,326)	(14,702)
Inventories, net	(428,405)	77,681
Increase (Decrease) in Other Operating Assets	19,299	(26,655)
Accounts payable	550,858	80,489
Accrued payroll and benefit costs	65,136	25,872
Other current and noncurrent liabilities	95,909	122,616
Net cash provided by operating activities	172,670	418,938
Investing Activities:
Capital expenditures	(25,170)	(42,562)
Payments to Acquire Businesses, Gross	0	(3,707,575)
Proceeds from Divestiture of Businesses, Net of Cash Divested	56,010	0
Other investing activities	5,766	26,240
Net cash used in investing activities	36,606	(3,723,897)
Financing Activities:
Proceeds from (Repayments of) Short-term Debt	(10,288)	(9,824)
Proceeds from issuance of long-term debt	2,470,306	4,661,830
Repayments of Other Long-term Debt	1,935,655	1,045,667
Payments for Repurchase of Common Stock	(20,784)	(2,032)
Payments of Dividends	(43,056)	(15,787)
Payments of Debt Issuance Costs	(1,849)	(79,945)
Other financing activities, net	(14,174)	(1,255)
Net cash used in financing activities	(410,204)	3,507,320
Effect of exchange rate on cash and cash equivalents	3,592	(1,014)
Cash and cash equivalents at the beginning of period	449,135	150,902
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect, Total	(197,336)	201,347
Cash and cash equivalents at the end of period	251,799	352,249
Interest Paid, Including Capitalized Interest, Operating and Investing Activities	141,594	36,035
Income Taxes Paid	53,759	44,994
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	120,384	80,626
5.375% Senior Notes due 2021
Financing Activities:
Repayments of Senior Debt	500,000	0
Repayments of Senior Debt	500,000	0
5.375% Senior Notes due 2024
Financing Activities:
Repayments of Senior Debt	354,704	0
Repayments of Senior Debt	$ 354,704	$ 0

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY Statement - USD ($) $ in Thousands	Total	Common Class B [Member]	Common Stock [Member]	Series A Preferred Stock [Member]	AOCI Attributable to Parent [Member]	Noncontrolling Interest [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Additional Paid-in Capital [Member]
Common stock		$ 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		$ 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)
Stock Issued During Period, Value, Purchase of Assets	82			$ 0					886,740
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, Shares, Purchase of Assets	8,150,228			21,612
Common stock		$ 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)
Stock Issued During Period, Value, Purchase of Assets									(139)
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
Common stock		$ 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
Common stock		$ 43	$ 676
Common Stock, Shares, Issued		4,339,431	67,596,515
Additional capital	1,942,810
Retained Earnings (Accumulated Deficit)	2,601,662
Treasury Stock, Value	$ (938,335)
ERROR in label resolution.	(21,870,961)
Stockholders' Equity Attributable to Noncontrolling Interest	$ (7,333)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(263,134)
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)			$ 2				$ (1,421)
APIC, Share-based Payment Arrangement, Recognition and Exercise	(38)
Shares Granted, Value, Share-based Payment Arrangement, after Forfeiture	5,954
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation			$ 0					617	2,209
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period			(165,641)				(15,330)
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation			(35,289)
Net Income (Loss) Attributable to Parent	59,178
Dividends, Preferred Stock	(14,352)
Net Income (Loss) Attributable to Noncontrolling Interest						(24)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax					16,841
Net Income (Loss) Attributable to Parent	297,969
Net Income (Loss) Attributable to Noncontrolling Interest	665
Common stock		$ 43	$ 678
Common Stock, Shares, Issued		4,339,431	67,726,867
Additional capital	1,946,517
Retained Earnings (Accumulated Deficit)	2,645,871
Treasury Stock, Value	$ (939,756)
ERROR in label resolution.	(21,886,291)
Stockholders' Equity Attributable to Noncontrolling Interest	$ (7,357)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(246,293)
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)			$ 2				$ (7,942)
APIC, Share-based Payment Arrangement, Recognition and Exercise	(1)
Shares Granted, Value, Share-based Payment Arrangement, after Forfeiture	7,225
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation			$ 0					49	88
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period			(194,615)				(74,698)
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation			(1,520)
Net Income (Loss) Attributable to Parent	119,195
Dividends, Preferred Stock				$ (14,352)
Net Income (Loss) Attributable to Noncontrolling Interest						89
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax					21,219
Common stock		$ 43	$ 680
Common Stock, Shares, Issued		4,339,431	67,919,962
Additional capital	1,953,653
Retained Earnings (Accumulated Deficit)	2,750,665
Treasury Stock, Value	$ (947,698)
ERROR in label resolution.	(21,960,989)
Stockholders' Equity Attributable to Noncontrolling Interest	$ (7,268)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(225,074)
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)			$ 2				$ (2,306)
APIC, Share-based Payment Arrangement, Recognition and Exercise	(2)
Shares Granted, Value, Share-based Payment Arrangement, after Forfeiture	9,605
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation			$ (1)					$ 4,162	$ 1,887
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period			(187,770)				(19,858)
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation			(58,214)
Net Income (Loss) Attributable to Parent	119,596
Dividends, Preferred Stock				$ (14,352)
Net Income (Loss) Attributable to Noncontrolling Interest	600					$ 600
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax					$ (50,277)
Common stock		$ 43	$ 681
Common Stock, Shares, Issued		4,339,431	68,049,518
Additional capital	1,961,369
Retained Earnings (Accumulated Deficit)	2,851,747
Treasury Stock, Value	$ (950,004)
ERROR in label resolution.	(21,980,847)
Stockholders' Equity Attributable to Noncontrolling Interest	$ (6,668)
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (275,351)
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	9 Months Ended
ORGANIZATION	Sep. 30, 2021
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.

ACCOUNTING POLICIES	9 Months Ended
ACCOUNTING POLICIES	Sep. 30, 2021
Accounting Policies [Abstract]
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 2020 Annual Report on Form 10-K as filed with the SEC on March 1, 2021. The Condensed Consolidated Balance Sheet at December 31, 2020 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, 2021, 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, 2021 and 2020, and the unaudited Condensed Consolidated Statements of Cash Flows for the nine months ended September 30, 2021 and 2020, respectively, in the opinion of management, have been prepared on the same basis as the audited Consolidated Financial Statements and include all adjustments necessary for the fair statement of the results of the interim periods presented herein. All adjustments reflected in the unaudited condensed consolidated financial information are of a normal recurring nature unless indicated. The results for the interim periods presented herein are not necessarily indicative of the results to be expected for the full year. Reclassifications For the nine months ended September 30, 2020, a gain on sale of assets of $19.8 million, stock-based compensation of $15.5 million, and amortization of debt discount and debt issuance costs of $6.3 million have been reclassified from other operating activities, net in the unaudited Condensed Consolidated Statement of Cash Flows. These reclassifications have been made to conform to the current period presentation. Change in Estimates During the second quarter of 2021, the Company established a new corporate brand strategy that will result in migrating certain legacy WESCO sub-brands to a master brand architecture. The Company accounts for the trademarks associated with these sub-brands as intangible assets. As of December 31, 2020, $39.1 million of the trademarks impacted by the master brand strategy had indefinite lives and $9.5 million had remaining estimated useful lives ranging from 3 to 8 years. The Company continually evaluates whether events or circumstances have occurred that would require a change to the estimated useful lives of indefinite-lived and definite lived intangible assets. When such a change is warranted, the remaining carrying amount of the intangible asset is amortized prospectively over the revised remaining useful life. Accordingly, during the second quarter of 2021, the Company changed the estimated useful lives of the trademarks affected by the new corporate brand strategy to coincide with the expected period of time to migrate such sub-brands to the master brand architecture. The Company assigned remaining estimated useful lives to these trademarks, including those that previously had indefinite lives, ranging from less than one year to 5 years. The Company assessed these intangible assets for impairment prior to amortizing them over their revised estimated remaining useful lives. No impairment losses were identified as a result of these tests. Recently Adopted Accounting Pronouncements In December 2019, the Financial Accounting Standards Board (the "FASB") issued Accounting Standards Update ("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 ("ASC") 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. The Company adopted this ASU in the first quarter of 2021. The adoption of this guidance did not have a material impact on the consolidated financial statements and notes thereto presented herein. Recently Issued Accounting Pronouncements 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.
Change in Accounting Estimate	Change in Estimates During the second quarter of 2021, the Company established a new corporate brand strategy that will result in migrating certain legacy WESCO sub-brands to a master brand architecture. The Company accounts for the trademarks associated with these sub-brands as intangible assets. As of December 31, 2020, $39.1 million of the trademarks impacted by the master brand strategy had indefinite lives and $9.5 million had remaining estimated useful lives ranging from 3 to 8 years. The Company continually evaluates whether events or circumstances have occurred that would require a change to the estimated useful lives of indefinite-lived and definite lived intangible assets. When such a change is warranted, the remaining carrying amount of the intangible asset is amortized prospectively over the revised remaining useful life. Accordingly, during the second quarter of 2021, the Company changed the estimated useful lives of the trademarks affected by the new corporate brand strategy to coincide with the expected period of time to migrate such sub-brands to the master brand architecture. The Company assigned remaining estimated useful lives to these trademarks, including those that previously had indefinite lives, ranging from less than one year to 5 years. The Company assessed these intangible assets for impairment prior to amortizing them over their revised estimated remaining useful lives. No impairment losses were identified as a result of these tests.
New Accounting Pronouncements and Changes in Accounting Principles [Text Block]	Recently Adopted Accounting Pronouncements In December 2019, the Financial Accounting Standards Board (the "FASB") issued Accounting Standards Update ("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 ("ASC") 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. The Company adopted this ASU in the first quarter of 2021. The adoption of this guidance did not have a material impact on the consolidated financial statements and notes thereto presented herein.

- Definition

The entire disclosure for change in accounting principle. Includes, but is not limited to, nature, reason, and method of adopting amendment to accounting standards or other change in accounting principle.

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+ Details

REVENUE (Notes)

9 Months Ended

Sep. 30, 2021

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 EES, CSS and UBS, operate in the United States, Canada and various other international countries.

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)	2021		2020		2021		2020
EES	$	1,982,485	$	1,653,726	$	5,626,309	$	3,811,498
CSS	1,488,689		1,388,791		4,200,424		1,953,967
UBS	1,257,151		1,099,284		3,538,859		2,431,689
Total by segment	$	4,728,325	$	4,141,801	$	13,365,592	$	8,197,154


	Three Months Ended				Nine Months Ended
	September 30				September 30
(In thousands)	2021		2020		2021		2020
United States	$	3,407,437	$	3,033,101	$	9,656,183	$	6,100,877
Canada	709,507		582,700		2,020,395		1,311,724
Other International(1)	611,381		526,000		1,689,014		784,553
Total by geography	$	4,728,325	$	4,141,801	$	13,365,592	$	8,197,154

(1) No individual country's net sales are greater than 10% of total net sales.

In accordance with certain contractual arrangements, WESCO receives payment from certain of 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, 2021 and December 31, 2020, $44.5 million and $24.3 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 historical data as well as current and forecasted information. 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, 2021 and 2020 by approximately $95.5 million and $75.4 million, respectively, and by approximately $274.7 million and $129.0 million for the nine months ended September 30, 2021 and 2020, respectively. As of September 30, 2021 and December 31, 2020, the Company's estimated product return obligation was $37.8 million and $38.9 million, respectively.Shipping and handling activities are recognized in net sales when they are billed to the customer. WESCO has elected to recognize shipping and handling costs as a fulfillment cost. Shipping and handling costs recorded as a component of selling, general and administrative expenses totaled $63.5 million and $55.5 million for the three months ended September 30, 2021 and 2020, respectively, and $179.5 million and $94.4 million for the nine months ended September 30, 2021 and 2020, respectively

- Definition

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

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+ Details

ACQUISITIONS

3 Months Ended

Sep. 30, 2020

Business Combinations [Abstract]

Business Combination Disclosure

Anixter International Inc.

On June 22, 2020, WESCO completed its acquisition of Anixter International Inc. ("Anixter"), a Delaware corporation. 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. On June 23, 2020, Anixter merged with and into Anixter Inc., with Anixter Inc. surviving to become a wholly owned subsidiary of WESCO.

The Company used the net proceeds from the issuance of senior unsecured notes, borrowings under its revolving credit and accounts receivable securitization facilities, 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 was 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 has afforded the Company the opportunity to digitize its business and expand its services portfolio and supply chain offerings.

The total 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 ASC 805, Business Combinations. Under the acquisition method of accounting, the 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 as Level 3 in the fair value hierarchy. Specifically, the fair values of the identified trademark and customer relationship intangible assets were estimated using the relief-from-royalty and multi-period excess earnings methods, respectively. Significant inputs used to value these identifiable intangible assets included projected revenues and expected operating margins, customer attrition rates, 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, "Goodwill and Intangible Assets". The resulting goodwill is primarily attributable to Anixter's workforce, significant cross-selling opportunities in additional geographies, enhanced scale, and other operational efficiencies.

During the second quarter of 2021, the Company finalized its allocation of the purchase consideration to the respective fair values of assets acquired and liabilities assumed in the acquisition of Anixter. As the Company obtained additional information during the measurement period (one year from the acquisition date), it recorded adjustments to its preliminary estimates of fair value, which are presented in the table below. The net impact of these adjustments was an increase to goodwill of $13.4 million in the second quarter of 2021 and $16.4 million since the Company's initial estimate.

The following table sets forth the allocation of the purchase consideration to the respective fair value of assets acquired and liabilities assumed for the acquisition of Anixter:


	Preliminary Fair Value Estimates		Measurement Period Adjustments		Final Purchase Price Allocation
Assets	(In thousands)
Cash and cash equivalents	$	103,463	$	—	$	103,463
Trade accounts receivable	1,309,894		(8,928)		1,300,966
Other accounts receivable	116,386		—		116,386
Inventories	1,424,768		(14,906)		1,409,862
Prepaid expenses and other current assets	53,462		14,202		67,664
Property, buildings and equipment	215,513		(3,792)		211,721
Operating lease assets	262,238		18,047		280,285
Intangible assets	1,832,700		5,365		1,838,065
Goodwill	1,367,981		16,356		1,384,337
Other assets	114,258		25,589		139,847
Total assets	$	6,800,663	$	51,933	$	6,852,596

Liabilities
Accounts payable	$	920,163	$	(1,239)	$	918,924
Accrued payroll and benefit costs	69,480		—		69,480
Short-term debt and current portion of long-term debt	13,225		—		13,225
Other current liabilities	221,574		12,745		234,319
Long-term debt	77,822		(205)		77,617
Operating lease liabilities	200,286		17,017		217,303
Deferred income taxes	392,165		(15,111)		377,054
Other noncurrent liabilities	207,612		38,726		246,338
Total liabilities	$	2,102,327	$	51,933	$	2,154,260

Fair value of net assets acquired, including goodwill and intangible assets	$	4,698,336	$	—	$	4,698,336

The following table sets forth the identifiable intangible assets and their estimated weighted-average useful lives:


Identifiable Intangible Assets	Estimated Fair Value		Weighted-Average Estimated Useful Life in Years(1)
	(In thousands)
Customer relationships	$	1,098,900	19
Trademarks	735,000		Indefinite
Non-compete agreements	4,165		2
Total identifiable intangible assets	$	1,838,065

(1) During the three months ended December 31, 2020, the Company recorded measurement period adjustments to the estimated useful lives initially assigned to customer relationships, which resulted in income of $6.4 million.

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, 2021, the condensed consolidated statements of income include $2.5 billion and $7.0 billion of net sales, respectively, and $165.8 million and $437.3 million of income from operations, respectively, for Anixter. 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, $80.0 million and $98.4 million of income from operations for Anixter. For the three months ended September 30, 2021 and 2020, the Company incurred costs related to the Merger of $35.8 million and $14.2 million, respectively, which primarily consist of advisory, legal, integration, separation and other costs. For the nine months ended September 30, 2021 and 2020, such costs were $119.8 million and $92.1 million, respectively. These costs are included in selling, general and administrative expenses for all periods presented.

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 9, "Employee Benefit Plans", as well as the respective income tax effects of such adjustments. For the three and nine months ended September 30, 2020, adjustments totaling $1.3 million and $5.5 million, respectively increased 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 periods, nor is it necessarily indicative of future results of operations of the combined company.


	Three Months Ended		Nine Months Ended
(In thousands)	September 30, 2020		September 30, 2020
Pro forma net sales(1)	$	4,141,801	$	11,888,061
Pro forma net income attributable to common stockholders(1)	66,651		112,717

(1) The Company reported pro forma net sales and pro forma net income attributable to common stockholders for the three and nine months ended September 30, 2020 in the Notes to Condensed Consolidated Financial Statements of its Quarterly Report on Form 10-Q for the period ended September 30, 2020 of $4,111.7 million and $11,802.5 million, respectively, and $63.8 million and $106.9 million, respectively. These amounts excluded the financial results of WESCO's legacy utility and data communications businesses in Canada, which were divested in the first quarter of 2021 under a Consent Agreement with the Competition Bureau of Canada, as described below.

Canadian Divestitures

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 was required to divest certain legacy WESCO utility and data communications businesses in Canada. In February 2021, the Company completed such divestitures for cash consideration totaling $56.0 million. The Company recognized a net gain from the sale of these businesses of $8.9 million, which is reported as a component of selling, general and administrative expenses for the nine months ended September 30, 2021. These sales fulfilled the Company’s divestiture commitments under the Consent Agreement and the net cash proceeds were used to repay debt.

GOODWILL (Notes)

9 Months Ended

Sep. 30, 2021

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill and Intangible Assets Disclosure

Goodwill

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


	Nine Months Ended
	September 30, 2021
	EES		CSS		UBS		Total
	(In thousands)
Beginning balance January 1(1)	$	853,456	$	1,115,500	$	1,218,213	$	3,187,169
Adjustments to goodwill for acquisitions (Note 4)(2)	1,124		8,602		4,215		13,941
Foreign currency exchange rate changes	1,679		(2,188)		1,087		578
Ending balance September 30	$	856,259	$	1,121,914	$	1,223,515	$	3,201,688

(1) The beginning balance excludes $26.1 million of goodwill that was classified as held for sale in the UBS segment as of December 31, 2020 and disposed in the first quarter of 2021 as part of the divestitures disclosed in Note 4, "Acquisitions and Disposals".

(2) Includes the effect on goodwill of the adjustments to the assets acquired and liabilities assumed in the merger with Anixter since their initial measurement, as described in Note 4, "Acquisitions and Disposals".

Intangible Assets

The components of intangible assets are as follows:


		September 30, 2021						December 31, 2020
	Life (in years)	Gross Carrying Amount (1)		Accumulated Amortization (1)		Net Carrying Amount		Gross Carrying Amount (1)		Accumulated Amortization (1)		Net Carrying Amount
Intangible assets:		(In thousands)
Trademarks	Indefinite	$	794,915	$	—	$	794,915	$	833,793	$	—	$	833,793
Customer relationships(2)	10 - 20	1,431,265		(287,565)		1,143,700		1,434,554		(227,585)		1,206,969
Distribution agreements(2)	10 - 19	29,212		(22,297)		6,915		29,212		(21,040)		8,172
Trademarks(2)	Less than 1 - 15	63,899		(32,964)		30,935		24,898		(11,415)		13,483
Non-compete agreements	2	4,292		(2,916)		1,376		4,462		(1,384)		3,078
		$	2,323,583	$	(345,742)	$	1,977,841	$	2,326,919	$	(261,424)	$	2,065,495

(1) Excludes the original cost and related accumulated amortization of fully-amortized intangible assets.

(2) The net carrying amount as of December 31, 2020 excluded $1.0 million of trademarks, $3.3 million of customer relationships and $1.4 million of distribution agreements that were classified as held for sale and disposed in the first quarter of 2021 as part of the divestitures disclosed in Note 4, "Acquisitions and Disposals".

Amortization expense related to intangible assets totaled $37.1 million and $27.3 million for the three months ended September 30, 2021 and 2020, respectively, and $85.8 million and $45.9 million for the nine months ended September 30, 2021 and 2020, respectively. For the three and nine months ended September 30, 2021, amortization expense includes $15.1 million and $20.2 million, respectively, resulting from the changes in estimated useful lives of certain legacy WESCO trademarks that are migrating to the Company's master brand architecture, as described in Note 2, "Accounting Policies".

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)
2021	$	33,814
2022	92,591
2023	83,294
2024	80,835
2025	77,719
Thereafter	814,673

STOCK-BASED COMPENSATION (Notes)

9 Months Ended

Sep. 30, 2021

Share-based Payment Arrangement [Abstract]

STOCK-BASED COMPENSATION

WESCO sponsors a stock-based compensation plan. On May 27, 2021, the Company's stockholders approved the WESCO International, Inc. 2021 Omnibus Incentive Plan (the “2021 Plan”). The 2021 Plan is administered by the Compensation Committee of the Company's Board of Directors.

The 2021 Plan was designed to be the successor plan to all prior stock-based compensation plans. Accordingly, no new awards may be granted under the Company’s 1999 Long-Term Incentive Plan, as amended and restated (the “1999 Plan”) or any other prior plan. Awards outstanding under any such prior plans will remain in full force and effect under such plans according to their respective terms. To the extent that any such award is forfeited, terminates, expires or lapses without being exercised, or is settled for cash, the shares subject to such award not delivered will again be available for awards under the 2021 Plan.

The maximum number of shares of the Company’s common stock that may be granted pursuant to awards under the 2021 Plan is 2,150,000, less any shares issued under the 1999 Plan between March 31, 2021 and May 27, 2021. If any award granted under the 2021 Plan is forfeited, terminates, expires or lapses instead of being exercised, or is settled for cash, the shares subject to such award will again be available for grant under the 2021 Plan. Shares delivered by participants or withheld by the Company to pay all or a portion of the exercise price or withholding taxes with respect to stock option or stock appreciation right awards will not again be available for issuance. Shares delivered by participants or withheld by the Company to satisfy applicable tax withholding obligations with respect to restricted shares or restricted stock units will again be available for grant under the 2021 Plan.

Stock-based employee compensation awards outstanding under WESCO's 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. Restricted stock unit awards granted in February 2020 and prior vest based on a minimum time period of three years. The special award described below vests in tranches. Restricted stock units awarded in 2021 vest ratably over a three-year period on each of the first, second and third anniversaries of the grant date. 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 2021, 2020 and 2019 are based on two equally-weighted performance measures: the three-year average growth rate of WESCO's net income attributable to common stockholders and the three-year cumulative return on net assets.

During the three and nine months ended September 30, 2021 and 2020, 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, 2021		September 30, 2020		September 30, 2021		September 30, 2020
Stock-settled stock appreciation rights granted	—		—		139,592		262,091
Weighted-average fair value	$	—	$	—	$	33.19	$	13.86

Restricted stock units granted	6,897		444,375		314,480		655,825
Weighted-average fair value	$	108.76	$	32.18	$	77.81	$	37.38

Performance-based awards granted	—		—		122,812		158,756
Weighted-average fair value	$	—	$	—	$	76.76	$	48.67

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


	Nine Months Ended
		September 30, 2021		September 30, 2020
Risk free interest rate		0.8	%	1.4	%
Expected life (in years)		7		5
Expected volatility		41	%	30	%

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 price over the expected life preceding the grant date of the award.

The following table sets forth a summary of stock-settled stock appreciation rights and related information for the nine months ended September 30, 2021:


	Awards	Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (In years)	Aggregate Intrinsic Value (In thousands)
Outstanding at December 31, 2020	2,161,556	$	60.48
Granted	139,592	77.05
Exercised	(671,272)	55.93
Forfeited	(12,719)	52.57
Outstanding at September 30, 2021	1,617,157	63.87		5.7	$	83,206
Exercisable at September 30, 2021	1,247,342	$	64.94	4.9	$	62,835

For the nine months ended September 30, 2021, the aggregate intrinsic value of stock-settled stock appreciation rights exercised during such period was $31.0 million.

The following table sets forth a summary of time-based restricted stock units and related information for the nine months ended September 30, 2021:


	Awards	Weighted- Average Fair Value
Unvested at December 31, 2020	921,495	$	43.15
Granted	314,480	77.81
Vested	(228,584)	44.02
Forfeited	(30,182)	62.68
Unvested at September 30, 2021	977,209	$	53.41

The following table sets forth a summary of performance-based awards for the nine months ended September 30, 2021:


	Awards	Weighted- Average Fair Value
Unvested at December 31, 2020	305,269	$	52.61
Granted	122,812	76.76
Vested	(22,371)	62.34
Forfeited	(27,802)	59.87
Unvested at September 30, 2021	377,908	$	59.35

Vesting of the 377,908 shares of performance-based awards in the table above is dependent upon the achievement of certain performance targets, including half that are dependent upon the three-year average growth rate of WESCO's net income attributable to common stockholders and the other half 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 $9.6 million and $6.0 million of non-cash stock-based compensation expense, which is included in selling, general and administrative expenses, for the three months ended September 30, 2021 and 2020, respectively. WESCO recognized $22.8 million and $15.5 million of non-cash stock-based compensation expense, which is included in selling, general and administrative expenses, for the nine months ended September 30, 2021 and 2020, respectively. As of September 30, 2021, there was $53.2 million of total unrecognized compensation expense related to non-vested stock-based compensation arrangements for all awards previously made of which approximately $8.0 million is expected to be recognized over the remainder of 2021, $26.4 million in 2022, $17.0 million in 2023 and $1.8 million in 2024.

EARNINGS PER SHARE

9 Months Ended

Sep. 30, 2021

Earnings Per Share [Abstract]

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)	2021		2020		2021		2020
Net income attributable to WESCO International, Inc.	$	119,596	$	80,678	$	297,969	$	80,578
Less: Preferred stock dividends	14,352		14,511		43,056		15,787
Net income attributable to common stockholders	$	105,244	$	66,167	$	254,913	$	64,791
Weighted-average common shares outstanding used in computing basic earnings per share	50,386		50,043		50,252		44,873
Common shares issuable upon exercise of dilutive equity awards	1,677		444		1,644		231
Weighted-average common shares outstanding and common share equivalents used in computing diluted earnings per share	52,063		50,487		51,896		45,104
Earnings per share attributable to common stockholders
Basic	$	2.09	$	1.32	$	5.07	$	1.44
Diluted	$	2.02	$	1.31	$	4.91	$	1.44

The computation of diluted earnings per share attributable to common stockholders excludes stock-based awards that would have an antidilutive effect on earnings per share. For the three months ended September 30, 2021, there were no antidilutive stock-based awards, and for the nine months then ended, there were approximately 0.1 million antidilutive awards. 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.

DEBT (Notes)

9 Months Ended

Sep. 30, 2021

Debt Instrument [Line Items]

Debt Disclosure [Text Block]

8. DEBT

The following table sets forth WESCO's outstanding indebtedness:


	As of
	September 30, 2021		December 31, 2020
	(In thousands)
International lines of credit	$	17,554	$	29,575
Accounts Receivable Securitization Facility	1,185,000		950,000
Revolving Credit Facility	550,000		250,000
5.375% Senior Notes due 2021	—		500,000
5.50% Anixter Senior Notes due 2023	58,636		58,636
5.375% Senior Notes due 2024	—		350,000
6.00% Anixter Senior Notes due 2025	4,173		4,173
7.125% Senior Notes due 2025	1,500,000		1,500,000
7.250% Senior Notes due 2028, less debt discount of $8,399 and $9,332 in 2021 and 2020, respectively	1,316,601		1,315,668
Finance lease obligations	17,792		17,931
Total debt	4,649,756		4,975,983
Plus: Fair value adjustment to the Anixter Senior Notes	1,131		1,650
Less: Unamortized debt issuance costs	(65,823)		(78,850)
Less: Short-term debt and current portion of long-term debt	(19,292)		(528,830)
Total long-term debt	$	4,565,772	$	4,369,953

Accounts Receivable Securitization Facility

On June 1, 2021, WESCO Distribution, Inc. ("WESCO Distribution") amended its accounts receivable securitization facility (the “Receivables Facility”) pursuant to the terms and conditions of a Third Amendment to the Fifth Amended and Restated Receivables Purchase Agreement (the “Receivables Amendment”), by and among WESCO Receivables Corp. (“WESCO Receivables”), WESCO Distribution, the various purchaser groups from time to time party thereto and PNC Bank, National Association, as Administrator. The Receivables Amendment amends the amended and restated receivables purchase agreement entered into on June 22, 2020 (the “Receivables Purchase Agreement”). The Receivables Amendment, among other things, increased the purchase limit under the Receivables Purchase Agreement from $1,200 million to $1,300 million, extended the maturity date from June 22, 2023 to June 21, 2024, decreased the LIBOR floor from 0.50% to 0.00% and decreased the interest rate spread from 1.20% to 1.15%. The commitment fee of the Receivables Facility remained unchanged.

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.

5.375% Senior Notes due 2021

In November 2013, WESCO Distribution issued $500 million aggregate principal amount of 5.375% Senior Notes due 2021 (the "2021 Notes") through a private offering exempt from the registration requirements of the Securities Act of 1933, as amended (the “Securities Act”). The 2021 Notes were issued at 100% of par and were governed by an indenture (the “2021 Indenture”) entered into on November 26, 2013 between WESCO Distribution, as issuer, and U.S. Bank National Association, as trustee. The 2021 Notes were unsecured senior obligations of WESCO Distribution and were guaranteed on a senior unsecured basis by WESCO International. The 2021 Notes had a stated interest rate of 5.375% per annum, payable semi-annually in arrears on June 15 and December 15 of each year. The 2021 Notes had a maturity date of December 15, 2021 and were redeemable in whole or in part at any time. The net proceeds of the 2021 Notes were used to prepay a portion of the U.S. sub-facility of the then outstanding term loan due 2019.

Under the terms of a registration rights agreement dated as of November 26, 2013 among WESCO Distribution, WESCO International and Merrill Lynch, Pierce, Fenner & Smith Incorporated, as the representative of the initial purchasers of the 2021 Notes, WESCO Distribution and WESCO International agreed to register under the Securities Act notes having terms identical in all material respects to the 2021 Notes (the “2021 Exchange Notes”) and to make an offer to exchange the 2021 Exchange Notes for the 2021 Notes. WESCO Distribution launched the exchange offer on June 12, 2014 and the exchange offer expired on July 17, 2014.

On December 15, 2020, WESCO Distribution exercised its right to redeem the entire $500 million aggregate principal amount of the 2021 Notes, and U.S. Bank, National Association, as trustee under the 2021 Indenture, issued a notice of redemption to registered holders of the 2021 Notes.

On January 14, 2021, WESCO Distribution redeemed the $500 million aggregate principal amount of the 2021 Notes at a redemption price equal to 100% of the principal amount plus accrued interest to, but not including, January 14, 2021. The redemption of the 2021 Notes was funded with available cash, as well as borrowings under the Company's Receivables Facility and revolving credit facility. The Company recognized a loss of $1.0 million from the redemption of the 2021 Notes resulting from the the write-off of unamortized debt issuance costs, which is recorded as a component of interest expense, net in the Condensed Consolidated Statement of Income and Comprehensive Income for the nine months ended September 30, 2021.

5.375% Senior Notes due 2024

In June 2016, WESCO Distribution issued $350 million aggregate principal amount of 5.375% Senior Notes due 2024 (the "2024 Notes") through a private offering exempt from the registration requirements of the Securities Act. The 2024 Notes were issued at 100% of par and were governed by an indenture (the “2024 Indenture”) entered into on June 15, 2016 among WESCO Distribution, as issuer, WESCO International, as parent guarantor, and U.S. Bank National Association, as trustee. The 2024 Notes were unsecured senior obligations of WESCO Distribution and were guaranteed on a senior unsecured basis by WESCO International. The 2024 Notes had a stated interest rate of of 5.375% per annum, payable semi-annually in arrears on June 15 and December 15 of each year. The 2024 Notes had a maturity date of June 15, 2024. The Company used the net proceeds from the 2024 Notes to redeem its 6.0% Convertible Senior Debentures due 2029.

Under the terms of a registration rights agreement dated as of June 15, 2016 among WESCO Distribution, as the issuer, WESCO International, as parent guarantor, and Goldman, Sachs & Co., as representative of the initial purchasers of the 2024 Notes, WESCO Distribution and WESCO International agreed to register under the Securities Act notes having terms identical in all material respects to the 2024 Notes (the “2024 Exchange Notes”) and to make an offer to exchange the 2024 Exchange Notes for the 2024 Notes. WESCO Distribution launched the exchange offer on December 28, 2016 and the exchange offer expired on January 31, 2017.

On June 2, 2021, WESCO Distribution exercised its right to redeem the entire $350 million aggregate principal amount of the 2024 Notes, and U.S. Bank, National Association, as trustee under the 2024 Indenture, issued a notice of redemption to registered holders of the 2024 Notes.

On July 2, 2021, WESCO Distribution redeemed the $350 million aggregate principal amount of the 2024 Notes at a redemption price equal to 101.344% of the principal amount plus accrued interest to, but not including, July 2, 2021. The redemption of the 2024 Notes was funded with borrowings under the Company's Receivables Facility and revolving credit facility. The Company recognized a loss on debt extinguishment totaling $6.9 million, which included $4.7 million for the premium paid to redeem the 2024 Notes and $2.2 million for the write-off of unamortized debt issuance costs. The loss was recorded as a component of interest expense, net in the Condensed Consolidated Statements of Income and Comprehensive Income for the three and nine months ended

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

+ Details

EMPLOYEE BENEFIT PLANS (Notes)

9 Months Ended

Sep. 30, 2021

Retirement Benefits [Abstract]

EMPLOYEE BENEFIT PLANS

9. EMPLOYEE BENEFIT PLANS

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.

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.

WESCO incurred charges of $16.4 million and $3.5 million for the three months ended September 30, 2021 and 2020, respectively, and $49.1 million and $12.6 million for the nine months ended September 30, 2021 and 2020, respectively, for all defined contribution plans.

Deferred Compensation Plans

WESCO Distribution sponsors a non-qualified 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, 2021, the Company's obligation under the WESCO Deferred Compensation Plan was $19.9 million, which is included in other noncurrent liabilities in the Condensed Consolidated Balance Sheet. As of December 31, 2020, the Company's obligation under the WESCO Deferred Compensation Plan was $27.4 million, of which $10.1 million was included in other current liabilities and $17.3 million was in other noncurrent liabilities in the Condensed Consolidated Balance Sheet.

Anixter Inc. sponsored a non-qualified deferred compensation plan (the "Anixter Deferred Compensation Plan") that permitted select employees to make pre-tax deferrals of salary and bonus. Interest was 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 was further adjusted if certain financial goals were achieved. In the fourth quarter of 2020, the Company terminated the Anixter Deferred Compensation Plan. Accordingly, the deferred compensation liability of $45.1 million was classified in other current liabilities in the Condensed Consolidated Balance Sheet at December 31, 2020. In the second quarter of 2021, the Company settled the liability for the Anixter Deferred Compensation Plan by making lump sum payments of $42.8 million directly to participants.

The Company held assets in a Rabbi Trust arrangement to provide for the liability associated with the Anixter Deferred Compensation Plan. The assets were invested in marketable securities. As of December 31, 2020, the assets held in this arrangement were $39.6 million and were recorded in other current assets in the Condensed Consolidated Balance Sheets. In the second quarter of 2021, the Company liquidated this investment arrangement for approximately $39.7 million and used the proceeds to fund the settlement of the Anixter Deferred Compensation Plan described above.

Defined Benefit Plans

WESCO sponsors a contributory defined benefit plan (the "EECOL Plan") covering substantially all Canadian employees of EECOL Electric Corp. and a Supplemental Executive Retirement Plan for certain executives of EECOL Electric Corp. (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 "Domestic Plans") and various defined benefit pension plans covering employees of foreign subsidiaries in Canada and Europe (together with the "EECOL Plan" and "EECOL SERP", the "Foreign Plans"). The Anixter Inc. Pension Plan was closed to entrants first hired or rehired on or after July 1, 2015. The majority of the Anixter defined benefit pension plans are non-contributory, and with the exception of U.S. and Canada, cover substantially all full-time employees in their respective countries. Retirement benefits are provided based on compensation as defined in each of the pension plans.

In the fourth quarter of 2020, the Company terminated both the Anixter Inc. Executive Benefit Plan and the Anixter SERP. Accordingly, pension liabilities totaling $18.1 million associated with the Anixter Inc. Executive Benefit Plan and the Anixter SERP were classified as current in the Condensed Consolidated Balance Sheet at December 31, 2020. In the second quarter of 2021, the Company settled its liability for the Anixter Inc. Executive Benefit Plan by making lump sum payments of $10.4 million directly to participants. The Company expects to make lump sum payments of $7.5 million directly to participants of the Anixter SERP in the fourth quarter of 2021.

The Domestic Plans are funded as required by the Employee Retirement Income Security Act of 1974 ("ERISA") and the Internal Revenue Service and the Foreign Plans are funded as required by applicable foreign laws. The EECOL SERP and the Anixter SERP are unfunded plans.

The Company made aggregate cash contributions to its Foreign Plans of $2.4 million and $2.2 million during the three months ended September 30, 2021 and 2020, respectively, and $8.1 million and $4.0 million during the nine months ended September 30, 2021 and 2020, respectively.

The following tables set forth the components of net periodic pension (benefit) cost for the Company's defined benefit plans:


	Three Months Ended
(In thousands)	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
	Domestic Plans(1)				Foreign Plans(1)				Total
Service cost	$	764	$	824	$	3,251	$	3,002	$	4,015	$	3,826
Interest cost	2,018		2,299		2,465		2,545		4,483		4,844
Expected return on plan assets	(4,414)		(4,041)		(4,277)		(4,358)		(8,691)		(8,399)
Recognized actuarial gain	—		—		103		(1)		103		(1)

Net periodic pension (benefit) cost	$	(1,632)	$	(918)	$	1,542	$	1,188	$	(90)	$	270


	Nine Months Ended
(In thousands)	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
	Domestic Plans(1)				Foreign Plans(1)				Total
Service cost	$	2,291	$	944	$	9,791	$	5,857	$	12,082	$	6,801
Interest cost	6,095		2,565		7,425		4,605		13,520		7,170
Expected return on plan assets	(13,241)		(4,498)		(12,898)		(7,503)		(26,139)		(12,001)
Recognized actuarial gain	—		—		311		52		311		52
Settlement	(19)		—		—		—		(19)		—
Net periodic pension (benefit) cost	$	(4,874)	$	(989)	$	4,629	$	3,011	$	(245)	$	2,022

(1) The Company assumed the Domestic Plans and certain of the Foreign Plans, as described above, in connection with the acquisition of Anixter on June 22, 2020. The Company began recognizing the net periodic pension (benefit) cost associated with these plans as of the acquisition date.

The service cost of $4.0 million and $3.8 million for the three months ended September 30, 2021 and 2020, respectively, and $12.1 million and $6.8 million for the nine months ended September 30, 2021 and 2020, respectively, is reported as a component of selling, general and administrative expenses. The other components of net periodic pension (benefit) cost totaling net benefits of $4.1 million and $3.6 million for the three months ended September 30, 2021 and 2020, respectively, and net benefits of $12.3 million and $4.8 million for the nine months ended September 30, 2021 and 2020, respectively, are presented as a component of other non-operating income ("other income, 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, 2021 and December 31, 2020, the estimated fair value of these awards was $20.5 million and $22.8 million, respectively. The Company recognized compensation expense associated with these awards of $3.4 million and $1.4 million for the three months ended September 30, 2021 and 2020, respectively, and $9.8 million and $2.3 million for the nine months ended September 30, 2021 and 2020, respectively, which is reported as a component of selling, general and administrative expenses.

STOCK-BASED COMPENSATION


	Three Months Ended				Nine Months Ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
Stock-settled stock appreciation rights granted	—		—		139,592		262,091
Weighted-average fair value	$	—	$	—	$	33.19	$	13.86

Restricted stock units granted	6,897		444,375		314,480		655,825
Weighted-average fair value	$	108.76	$	32.18	$	77.81	$	37.38

Performance-based awards granted	—		—		122,812		158,756
Weighted-average fair value	$	—	$	—	$	76.76	$	48.67

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


	Nine Months Ended
		September 30, 2021		September 30, 2020
Risk free interest rate		0.8	%	1.4	%
Expected life (in years)		7		5
Expected volatility		41	%	30	%

The following table sets forth a summary of stock-settled stock appreciation rights and related information for the nine months ended September 30, 2021:


	Awards	Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (In years)	Aggregate Intrinsic Value (In thousands)
Outstanding at December 31, 2020	2,161,556	$	60.48
Granted	139,592	77.05
Exercised	(671,272)	55.93
Forfeited	(12,719)	52.57
Outstanding at September 30, 2021	1,617,157	63.87		5.7	$	83,206
Exercisable at September 30, 2021	1,247,342	$	64.94	4.9	$	62,835

For the nine months ended September 30, 2021, the aggregate intrinsic value of stock-settled stock appreciation rights exercised during such period was $31.0 million.

The following table sets forth a summary of time-based restricted stock units and related information for the nine months ended September 30, 2021:


	Awards	Weighted- Average Fair Value
Unvested at December 31, 2020	921,495	$	43.15
Granted	314,480	77.81
Vested	(228,584)	44.02
Forfeited	(30,182)	62.68
Unvested at September 30, 2021	977,209	$	53.41

The following table sets forth a summary of performance-based awards for the nine months ended September 30, 2021:


	Awards	Weighted- Average Fair Value
Unvested at December 31, 2020	305,269	$	52.61
Granted	122,812	76.76
Vested	(22,371)	62.34
Forfeited	(27,802)	59.87
Unvested at September 30, 2021	377,908	$	59.35

Compensation Related Costs, General

Other Benefits

- Definition

The entire disclosure for retirement benefits.

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+ Details

FAIR VALUE (Notes)	9 Months Ended
FAIR VALUE (Notes)	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	10. FAIR VALUE OF FINANCIAL INSTRUMENTS The Company’s financial instruments primarily consist of cash and cash equivalents, accounts receivable, accounts payable, bank overdrafts, outstanding indebtedness, foreign currency forward contracts, and benefit plan assets. Except for benefit plan assets, outstanding indebtedness and foreign currency forward contracts, the carrying value of the Company’s remaining financial instruments approximates fair value. The assets of the Company's various defined benefit plans are primarily comprised of common/collective/pool funds (i.e., mutual funds). These funds are valued at the net asset value (NAV) of shares held in the underlying funds. Investments for which fair value is measured using the NAV per share practical expedient are not classified in the fair value hierarchy. 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 $2,880.5 million and $3,730.1 million as of September 30, 2021 and December 31, 2020, respectively. The estimated fair value of this debt was $3,139.7 million and $4,084.7 million as of September 30, 2021 and December 31, 2020, respectively. The reported carrying values of WESCO's other debt instruments, including those with variable interest rates, approximated their fair values as of September 30, 2021 and December 31, 2020. The Company purchases foreign currency forward contracts to minimize the effect of fluctuating foreign currency-denominated accounts on its earnings. 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 that could affect the value of its 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 are considered Level 2 in the fair value hierarchy. At September 30, 2021, 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 income, net") in the Condensed Consolidated Statements of Income and Comprehensive Income (Loss) offsetting the transaction gain (loss) recorded on foreign currency-denominated accounts. At September 30, 2021 and December 31, 2020, the gross and net notional amounts of foreign currency forward contracts outstanding were approximately $200.5 million and $111.9 million, respectively. 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 earnings. 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 that could affect the value of its 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 are considered Level 2 in the fair value hierarchy. At September 30, 2021, 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 income, net") in the Condensed Consolidated Statements of Income and Comprehensive Income (Loss) offsetting the transaction gain (loss) recorded on foreign currency-denominated accounts. At September 30, 2021 and December 31, 2020, the gross and net notional amounts of foreign currency forward contracts outstanding were approximately $200.5 million and $111.9 million, respectively. 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.

- Definition

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

+ References + Details

COMMITMENTS AND CONTINGENCIES	9 Months Ended
COMMITMENTS AND CONTINGENCIES	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
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.

INCOME TAXES	9 Months Ended
INCOME TAXES	Sep. 30, 2021
Income Tax Disclosure [Abstract]
INCOME TAXES	The effective tax rate for the three and nine months ended September 30, 2021 was 27.2% and 22.0%, respectively. The effective tax rate for the three and nine months ended September 30, 2020 was 23.3% and 22.9%, respectively. WESCO’s effective tax rate typically differs from the federal statutory income tax rate due to the tax effect of intercompany financing, foreign tax rate differences, the U.S. taxes imposed on foreign income, nondeductible expenses and state income taxes. The effective tax rate for the three months ended September 30, 2021 is higher than the corresponding quarter of the prior year primarily due to the impact on the estimated annual effective tax rate of a decrease in expected foreign tax credit utilization. For the nine months ended September 30, 2021, the effective tax rate reflects discrete income tax benefits resulting from a decrease in the valuation allowance recorded against foreign tax credit carryforwards of $8.3 million and deductible stock-based compensation of $7.8 million, which were partially offset by discrete income tax expense of $4.2 million associated with return-to-provision adjustments. These discrete items reduced the estimated annual effective tax rate by approximately 3.1 percentage points. There have been no material adjustments to liabilities for uncertain tax positions since the last annual disclosure for the year ended December 31, 2020.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

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+ Details

Segment Reporting

9 Months Ended

Sep. 30, 2021

Segment Reporting [Abstract]

Segment Reporting Disclosure

13. BUSINESS SEGMENTS

The Company has operating segments that are organized around three strategic business units consisting of EES, CSS and UBS. These operating segments are equivalent to the Company's reportable segments. The Company's CODM evaluates the performance of its operating segments based primarily on net sales, income from operations, and total assets.

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 are shown in the tables below to reconcile the reportable segments to the consolidated financial statements.

The following tables set forth financial information by reportable segment for the periods presented:


(In thousands)	Three Months Ended September 30, 2021
	EES		CSS		UBS		Corporate		Total
Net sales	$	1,982,485	$	1,488,689	$	1,257,151	$	—	$	4,728,325
Income from operations	155,210		108,226		108,172		(142,142)		229,466

	Three Months Ended September 30, 2020
(In thousands)	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


(In thousands)	Nine Months Ended September 30, 2021
	EES		CSS		UBS		Corporate		Total
Net sales	$	5,626,309	$	4,200,424	$	3,538,859	$	—	$	13,365,592
Income from operations	409,062		293,446		289,895		(410,814)		581,589

	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

There were no material changes to the amounts of total assets by reportable segment from those disclosed in the Company's Annual Report on Form 10-K for the fiscal year ended December 31, 2020.

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8924-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8981-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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-Section 50
-Paragraph 21
-Subparagraph (a)
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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-Section 50
-Paragraph 32
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8657-108599

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8721-108599

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-URI http://asc.fasb.org/topic&trid=2134510

+ Details

Subsequent Events (Notes)	9 Months Ended
Subsequent Events (Notes)	Sep. 30, 2021
Subsequent Events [Abstract]
Subsequent Events [Text Block]	14. SUBSEQUENT EVENTS

ACCOUNTING POLICIES (Policies)	9 Months Ended
ACCOUNTING POLICIES (Policies)	Sep. 30, 2021
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 2020 Annual Report on Form 10-K as filed with the SEC on March 1, 2021. The Condensed Consolidated Balance Sheet at December 31, 2020 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, 2021, 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, 2021 and 2020, and the unaudited Condensed Consolidated Statements of Cash Flows for the nine months ended September 30, 2021 and 2020, respectively, in the opinion of management, have been prepared on the same basis as the audited Consolidated Financial Statements and include all adjustments necessary for the fair statement of the results of the interim periods presented herein. All adjustments reflected in the unaudited condensed consolidated financial information are of a normal recurring nature unless indicated. The results for the interim periods presented herein are not necessarily indicative of the results to be expected for the full year.
Reclassifications [Text Block]	Reclassifications For the nine months ended September 30, 2020, a gain on sale of assets of $19.8 million, stock-based compensation of $15.5 million, and amortization of debt discount and debt issuance costs of $6.3 million have been reclassified from other operating activities, net in the unaudited Condensed Consolidated Statement of Cash Flows. These reclassifications have been made to conform to the current period presentation. Change in Estimates During the second quarter of 2021, the Company established a new corporate brand strategy that will result in migrating certain legacy WESCO sub-brands to a master brand architecture. The Company accounts for the trademarks associated with these sub-brands as intangible assets. As of December 31, 2020, $39.1 million of the trademarks impacted by the master brand strategy had indefinite lives and $9.5 million had remaining estimated useful lives ranging from 3 to 8 years. The Company continually evaluates whether events or circumstances have occurred that would require a change to the estimated useful lives of indefinite-lived and definite lived intangible assets. When such a change is warranted, the remaining carrying amount of the intangible asset is amortized prospectively over the revised remaining useful life. Accordingly, during the second quarter of 2021, the Company changed the estimated useful lives of the trademarks affected by the new corporate brand strategy to coincide with the expected period of time to migrate such sub-brands to the master brand architecture. The Company assigned remaining estimated useful lives to these trademarks, including those that previously had indefinite lives, ranging from less than one year to 5 years. The Company assessed these intangible assets for impairment prior to amortizing them over their revised estimated remaining useful lives. No impairment losses were identified as a result of these tests.
New Accounting Pronouncements and Changes in Accounting Principles [Text Block]	Recently Adopted Accounting Pronouncements In December 2019, the Financial Accounting Standards Board (the "FASB") issued Accounting Standards Update ("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 ("ASC") 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. The Company adopted this ASU in the first quarter of 2021. The adoption of this guidance did not have a material impact on the consolidated financial statements and notes thereto presented herein.
New Accounting Pronouncements, Policy	Recently Issued Accounting Pronouncements 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.

- Definition

+ References

+ Details

REVENUE (Tables)

9 Months Ended

Sep. 30, 2021

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)	2021		2020		2021		2020
EES	$	1,982,485	$	1,653,726	$	5,626,309	$	3,811,498
CSS	1,488,689		1,388,791		4,200,424		1,953,967
UBS	1,257,151		1,099,284		3,538,859		2,431,689
Total by segment	$	4,728,325	$	4,141,801	$	13,365,592	$	8,197,154


	Three Months Ended				Nine Months Ended
	September 30				September 30
(In thousands)	2021		2020		2021		2020
United States	$	3,407,437	$	3,033,101	$	9,656,183	$	6,100,877
Canada	709,507		582,700		2,020,395		1,311,724
Other International(1)	611,381		526,000		1,689,014		784,553
Total by geography	$	4,728,325	$	4,141,801	$	13,365,592	$	8,197,154

ACQUISITIONS (Tables)

9 Months Ended

Sep. 30, 2021

Business Combinations [Abstract]

Business Acquisition, Schedule of Consideration Transferred

The total 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 allocation of the purchase consideration to the respective fair value of assets acquired and liabilities assumed for the acquisition of Anixter:


	Preliminary Fair Value Estimates		Measurement Period Adjustments		Final Purchase Price Allocation
Assets	(In thousands)
Cash and cash equivalents	$	103,463	$	—	$	103,463
Trade accounts receivable	1,309,894		(8,928)		1,300,966
Other accounts receivable	116,386		—		116,386
Inventories	1,424,768		(14,906)		1,409,862
Prepaid expenses and other current assets	53,462		14,202		67,664
Property, buildings and equipment	215,513		(3,792)		211,721
Operating lease assets	262,238		18,047		280,285
Intangible assets	1,832,700		5,365		1,838,065
Goodwill	1,367,981		16,356		1,384,337
Other assets	114,258		25,589		139,847
Total assets	$	6,800,663	$	51,933	$	6,852,596

Liabilities
Accounts payable	$	920,163	$	(1,239)	$	918,924
Accrued payroll and benefit costs	69,480		—		69,480
Short-term debt and current portion of long-term debt	13,225		—		13,225
Other current liabilities	221,574		12,745		234,319
Long-term debt	77,822		(205)		77,617
Operating lease liabilities	200,286		17,017		217,303
Deferred income taxes	392,165		(15,111)		377,054
Other noncurrent liabilities	207,612		38,726		246,338
Total liabilities	$	2,102,327	$	51,933	$	2,154,260

Fair value of net assets acquired, including goodwill and intangible assets	$	4,698,336	$	—	$	4,698,336

Finite-Lived and Indefinite-Lived Intangible Assets Acquired as Part of Business Combination

The following table sets forth the identifiable intangible assets and their estimated weighted-average useful lives:


Identifiable Intangible Assets	Estimated Fair Value		Weighted-Average Estimated Useful Life in Years(1)
	(In thousands)
Customer relationships	$	1,098,900	19
Trademarks	735,000		Indefinite
Non-compete agreements	4,165		2
Total identifiable intangible assets	$	1,838,065

Business Acquisition, Pro Forma Information

Pro Forma Financial Information


	Three Months Ended		Nine Months Ended
(In thousands)	September 30, 2020		September 30, 2020
Pro forma net sales(1)	$	4,141,801	$	11,888,061
Pro forma net income attributable to common stockholders(1)	66,651		112,717

GOODWILL (Tables)

3 Months Ended

9 Months Ended

Sep. 30, 2021

Goodwill [Line Items]

Schedule of Goodwill [Table Text Block]


	Nine Months Ended
	September 30, 2021
	EES		CSS		UBS		Total
	(In thousands)
Beginning balance January 1(1)	$	853,456	$	1,115,500	$	1,218,213	$	3,187,169
Adjustments to goodwill for acquisitions (Note 4)(2)	1,124		8,602		4,215		13,941
Foreign currency exchange rate changes	1,679		(2,188)		1,087		578
Ending balance September 30	$	856,259	$	1,121,914	$	1,223,515	$	3,201,688

Schedule of Finite-Lived Intangible Assets

The components of intangible assets are as follows:


		September 30, 2021						December 31, 2020
	Life (in years)	Gross Carrying Amount (1)		Accumulated Amortization (1)		Net Carrying Amount		Gross Carrying Amount (1)		Accumulated Amortization (1)		Net Carrying Amount
Intangible assets:		(In thousands)
Trademarks	Indefinite	$	794,915	$	—	$	794,915	$	833,793	$	—	$	833,793
Customer relationships(2)	10 - 20	1,431,265		(287,565)		1,143,700		1,434,554		(227,585)		1,206,969
Distribution agreements(2)	10 - 19	29,212		(22,297)		6,915		29,212		(21,040)		8,172
Trademarks(2)	Less than 1 - 15	63,899		(32,964)		30,935		24,898		(11,415)		13,483
Non-compete agreements	2	4,292		(2,916)		1,376		4,462		(1,384)		3,078
		$	2,323,583	$	(345,742)	$	1,977,841	$	2,326,919	$	(261,424)	$	2,065,495

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)
2021	$	33,814
2022	92,591
2023	83,294
2024	80,835
2025	77,719
Thereafter	814,673

STOCK-BASED COMPENSATION (Tables)

9 Months Ended

Sep. 30, 2021

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

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


	Three Months Ended				Nine Months Ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
Stock-settled stock appreciation rights granted	—		—		139,592		262,091
Weighted-average fair value	$	—	$	—	$	33.19	$	13.86

Restricted stock units granted	6,897		444,375		314,480		655,825
Weighted-average fair value	$	108.76	$	32.18	$	77.81	$	37.38

Performance-based awards granted	—		—		122,812		158,756
Weighted-average fair value	$	—	$	—	$	76.76	$	48.67

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, 2021:


	Awards	Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (In years)	Aggregate Intrinsic Value (In thousands)
Outstanding at December 31, 2020	2,161,556	$	60.48
Granted	139,592	77.05
Exercised	(671,272)	55.93
Forfeited	(12,719)	52.57
Outstanding at September 30, 2021	1,617,157	63.87		5.7	$	83,206
Exercisable at September 30, 2021	1,247,342	$	64.94	4.9	$	62,835

For the nine months ended September 30, 2021, the aggregate intrinsic value of stock-settled stock appreciation rights exercised during such period was $31.0 million.

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, 2021:


	Awards	Weighted- Average Fair Value
Unvested at December 31, 2020	921,495	$	43.15
Granted	314,480	77.81
Vested	(228,584)	44.02
Forfeited	(30,182)	62.68
Unvested at September 30, 2021	977,209	$	53.41

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, 2021:


	Awards	Weighted- Average Fair Value
Unvested at December 31, 2020	305,269	$	52.61
Granted	122,812	76.76
Vested	(22,371)	62.34
Forfeited	(27,802)	59.87
Unvested at September 30, 2021	377,908	$	59.35

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:


	Nine Months Ended
		September 30, 2021		September 30, 2020
Risk free interest rate		0.8	%	1.4	%
Expected life (in years)		7		5
Expected volatility		41	%	30	%

EARNINGS PER SHARE (Tables)

9 Months Ended

Sep. 30, 2021

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)	2021		2020		2021		2020
Net income attributable to WESCO International, Inc.	$	119,596	$	80,678	$	297,969	$	80,578
Less: Preferred stock dividends	14,352		14,511		43,056		15,787
Net income attributable to common stockholders	$	105,244	$	66,167	$	254,913	$	64,791
Weighted-average common shares outstanding used in computing basic earnings per share	50,386		50,043		50,252		44,873
Common shares issuable upon exercise of dilutive equity awards	1,677		444		1,644		231
Weighted-average common shares outstanding and common share equivalents used in computing diluted earnings per share	52,063		50,487		51,896		45,104
Earnings per share attributable to common stockholders
Basic	$	2.09	$	1.32	$	5.07	$	1.44
Diluted	$	2.02	$	1.31	$	4.91	$	1.44

DEBT (Tables)

9 Months Ended

Sep. 30, 2021

Debt Disclosure [Abstract]

Schedule of Debt

The following table sets forth WESCO's outstanding indebtedness:


	As of
	September 30, 2021		December 31, 2020
	(In thousands)
International lines of credit	$	17,554	$	29,575
Accounts Receivable Securitization Facility	1,185,000		950,000
Revolving Credit Facility	550,000		250,000
5.375% Senior Notes due 2021	—		500,000
5.50% Anixter Senior Notes due 2023	58,636		58,636
5.375% Senior Notes due 2024	—		350,000
6.00% Anixter Senior Notes due 2025	4,173		4,173
7.125% Senior Notes due 2025	1,500,000		1,500,000
7.250% Senior Notes due 2028, less debt discount of $8,399 and $9,332 in 2021 and 2020, respectively	1,316,601		1,315,668
Finance lease obligations	17,792		17,931
Total debt	4,649,756		4,975,983
Plus: Fair value adjustment to the Anixter Senior Notes	1,131		1,650
Less: Unamortized debt issuance costs	(65,823)		(78,850)
Less: Short-term debt and current portion of long-term debt	(19,292)		(528,830)
Total long-term debt	$	4,565,772	$	4,369,953

EMPLOYEE BENEFIT PLANS Schedule of Net Benefit Costs (Tables)

9 Months Ended

Sep. 30, 2021

Postemployment Benefits [Abstract]

Schedule of Net Benefit Costs [Table Text Block]

The following tables set forth the components of net periodic pension (benefit) cost for the Company's defined benefit plans:


	Three Months Ended
(In thousands)	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
	Domestic Plans(1)				Foreign Plans(1)				Total
Service cost	$	764	$	824	$	3,251	$	3,002	$	4,015	$	3,826
Interest cost	2,018		2,299		2,465		2,545		4,483		4,844
Expected return on plan assets	(4,414)		(4,041)		(4,277)		(4,358)		(8,691)		(8,399)
Recognized actuarial gain	—		—		103		(1)		103		(1)

Net periodic pension (benefit) cost	$	(1,632)	$	(918)	$	1,542	$	1,188	$	(90)	$	270


	Nine Months Ended
(In thousands)	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
	Domestic Plans(1)				Foreign Plans(1)				Total
Service cost	$	2,291	$	944	$	9,791	$	5,857	$	12,082	$	6,801
Interest cost	6,095		2,565		7,425		4,605		13,520		7,170
Expected return on plan assets	(13,241)		(4,498)		(12,898)		(7,503)		(26,139)		(12,001)
Recognized actuarial gain	—		—		311		52		311		52
Settlement	(19)		—		—		—		(19)		—
Net periodic pension (benefit) cost	$	(4,874)	$	(989)	$	4,629	$	3,011	$	(245)	$	2,022

Segment Reporting (Tables)

9 Months Ended

Sep. 30, 2021

Segment Reporting [Abstract]

Reconciliation of Revenue from Segments to Consolidated

The following tables set forth financial information by reportable segment for the periods presented:


(In thousands)	Three Months Ended September 30, 2021
	EES		CSS		UBS		Corporate		Total
Net sales	$	1,982,485	$	1,488,689	$	1,257,151	$	—	$	4,728,325
Income from operations	155,210		108,226		108,172		(142,142)		229,466

	Three Months Ended September 30, 2020
(In thousands)	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


(In thousands)	Nine Months Ended September 30, 2021
	EES		CSS		UBS		Corporate		Total
Net sales	$	5,626,309	$	4,200,424	$	3,538,859	$	—	$	13,365,592
Income from operations	409,062		293,446		289,895		(410,814)		581,589

	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

Schedule of Segment Reporting Information, by Segment

The following tables set forth financial information by reportable segment for the periods presented:


(In thousands)	Three Months Ended September 30, 2021
	EES		CSS		UBS		Corporate		Total
Net sales	$	1,982,485	$	1,488,689	$	1,257,151	$	—	$	4,728,325
Income from operations	155,210		108,226		108,172		(142,142)		229,466

	Three Months Ended September 30, 2020
(In thousands)	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


(In thousands)	Nine Months Ended September 30, 2021
	EES		CSS		UBS		Corporate		Total
Net sales	$	5,626,309	$	4,200,424	$	3,538,859	$	—	$	13,365,592
Income from operations	409,062		293,446		289,895		(410,814)		581,589

	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

ACCOUNTING POLICIES (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
ACCOUNTING POLICIES (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Prepaid expenses and other current assets	$ 114,670		$ 114,670				$ 187,910
Assets, Current	6,215,496		6,215,496				5,506,978
Goodwill	3,201,688		3,201,688				3,187,169
Liabilities and Equity	12,481,018		12,481,018				11,880,214
Liabilities, Current	3,138,099		3,138,099				2,986,995
Assets	12,481,018		12,481,018				11,880,214
Liabilities	8,899,201		8,899,201				8,543,825
Retained earnings	2,851,747	$ 2,596,022	2,851,747	$ 2,596,022	$ 2,750,665	$ 2,645,871	2,601,662	$ 2,529,842	$ 2,565,597	$ 2,530,429
Accumulated other comprehensive income	(275,351)	(377,461)	(275,351)	(377,461)	$ (225,074)	$ (246,293)	(263,134)	$ (418,889)	$ (461,623)	$ (367,772)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	3,581,817		3,581,817				$ 3,336,389
Other Nonoperating Income (Expense)	(5,320)	(777)	(8,929)	(1,463)
Stock-based compensation expense	$ 9,600	$ 6,000	22,784	15,529
Amortization of Debt Issuance Costs and Discounts			$ 15,290	6,301
Change in Accounting Estimate, Description			As of December 31, 2020, $39.1 million of the trademarks impacted by the master brand strategy had indefinite lives and $9.5 million had remaining estimated useful lives ranging from 3 to 8 years. The Company continually evaluates whether events or circumstances have occurred that would require a change to the estimated useful lives of indefinite-lived and definite lived intangible assets.
Gain (Loss) on Disposition of Business			$ (8,927)	$ (19,816)

REVENUE (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
REVENUE (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Deferred Revenue	$ 44,500		$ 44,500		$ 24,300
Revenue from Contract with Customer, Excluding Assessed Tax	4,728,325	$ 4,141,801	13,365,592	$ 8,197,154
Cost of goods sold	3,720,332	$ 3,356,259	10,581,406	6,641,438
Contract with Customer, Refund Liability	$ 37,800		37,800		$ 38,900
Revenue, Information Used to Assess Variable Consideration Constraint	95.5 million	75.4 million
EES
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 1,982,485	$ 1,653,726	5,626,309	3,811,498
CSS
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,488,689	1,388,791	4,200,424	1,953,967
UBS
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,257,151	1,099,284	3,538,859	2,431,689
UNITED STATES
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3,407,437	3,033,101	9,656,183	6,100,877
CANADA
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	709,507	582,700	2,020,395	1,311,724
Non-US [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	611,381	526,000	1,689,014	784,553
Shipping and Handling [Member]
Disaggregation of Revenue [Line Items]
Cost of goods sold	$ 63,500	$ 55,500	$ 179,500	$ 94,400

REVENUE Deferred Revenue (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Deferred Revenue	$ 44.5	$ 24.3

REVENUE Shipping and Handling Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Cost of goods sold	$ 3,720,332	$ 3,356,259	$ 10,581,406	$ 6,641,438
Shipping and Handling [Member]
Cost of goods sold	$ 63,500	$ 55,500	$ 179,500	$ 94,400

REVENUE Variable Consideration (Details)	3 Months Ended
REVENUE Variable Consideration (Details)	Sep. 30, 2021	Sep. 30, 2020
Revenue, Methods, Inputs, and Assumptions Used [Abstract]
Revenue, Information Used to Assess Variable Consideration Constraint	95.5 million	75.4 million

REVENUE Revenue, Performance Obligation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenue from Contract with Customer [Abstract]
Cost of goods sold	$ 3,720,332	$ 3,356,259	$ 10,581,406	$ 6,641,438

SCHEDULE OF CONSIDERATION TRANSFERRED (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	$ 0	$ 3,707,575
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

SCHEDULE OF ASSETS AND LIABILITIES - ANIXTER (Details) - USD ($) $ in Thousands	6 Months Ended	9 Months Ended
	Jun. 30, 2021	Sep. 30, 2021	Jun. 22, 2021	Dec. 31, 2020	Jun. 22, 2020
Business Acquisition [Line Items]
Goodwill		$ 3,201,688		$ 3,187,169
Anixter International
Business Acquisition [Line Items]
Cash and cash equivalents			$ 103,463		$ 103,463
Trade accounts receivable			1,300,966		1,309,894
Other accounts receivable			116,386		116,386
Inventories			1,409,862		1,424,768
Prepaid expenses and other current assets			67,664		53,462
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Property, Plant, and Equipment		(3,792)
Property, buildings and equipment			211,721		215,513
Operating lease assets			280,285		262,238
Intangible assets			1,838,065		1,832,700
Goodwill			1,384,337		1,367,981
Other assets			139,847		114,258
Total assets			6,852,596		6,800,663
Accounts payable			918,924		920,163
Accrued payroll and benefit costs			69,480		69,480
Short-term debt and current portion of long-term debt			13,225		13,225
BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentCurrentLiabilitiesOther		12,745
Other current liabilities			234,319		221,574
BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentNoncurrentLiabilitiesLongTermDebt		(205)
Long-term debt			77,617		77,822
Operating lease liabilities			217,303		200,286
Deferred income taxes			377,054		392,165
Other noncurrent liabilities			246,338		207,612
Total liabilities			2,154,260		2,102,327
Fair value of net assets acquired, including goodwill and intangible assets			$ 4,698,336		$ 4,698,336
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Inventory		(14,906)
BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustments		14,202
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Intangibles	$ 6,400	5,365
BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOperatingLeaseAssets		18,047
BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOtherNoncurrentLiabilities		38,726
BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentsLiabilities		51,933
BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentDeferredIncomeTaxes		(15,111)
BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentOperatingLeaseLiabilities		17,017
Goodwill, Purchase Accounting Adjustments		16,356
BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentsNoncurrentAssets		25,589
BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentsAssets		51,933
BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccountsPayable		(1,239)
BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccountsReceivable		$ (8,928)

SCHEDULE OF IDENTIFIABLE INTANGIBLE ASSETS (Details) - Anixter International - USD ($) $ in Thousands	6 Months Ended	9 Months Ended
	Jun. 30, 2021	Sep. 30, 2021	Jun. 22, 2021	Jun. 22, 2020
Business Acquisition [Line Items]
Intangible assets			$ 1,838,065	$ 1,832,700
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Intangibles	$ 6,400	$ 5,365
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		19 years
Noncompete Agreements [Member]
Business Acquisition [Line Items]
Acquired Finite-Lived Intangibles			$ 4,165
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life		2 years

SCHEDULE OF PRO FORMA INFORMATION (Details) - Anixter International - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Business Acquisition [Line Items]
Pro forma net sales		$ 4,141,801		$ 11,888,061
Pro forma net income attributable to common stockholders		66,651		112,717
Business Combination, Acquisition Related Costs	$ 35,800	$ 14,200	$ 119,800	$ 92,100
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 9, "Employee Benefit Plans", as well as the respective income tax effects of such adjustments. For the three and nine months ended September 30, 2020, adjustments totaling $1.3 million and $5.5 million, respectively increased 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 periods, nor is it necessarily indicative of future results of operations of the combined company.

ACQUISITIONS (Details)		3 Months Ended		9 Months Ended
ACQUISITIONS (Details)	Jun. 22, 2020 USD ($) $ / shares shares	Sep. 30, 2021 USD ($) numberOfCities countries	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) numberOfCities countries	Sep. 30, 2020 USD ($)
Business Acquisition [Line Items]
Number of Cities in which an Entity Operates \| numberOfCities		300		300
Revenue from Contract with Customer, Excluding Assessed Tax		$ 4,728,325,000	$ 4,141,801,000	$ 13,365,592,000	$ 8,197,154,000
Operating Income (Loss)		229,466,000	178,095,000	581,589,000	254,278,000
Revenues		$ 4,728,325,000	4,141,801,000	$ 13,365,592,000	8,197,154,000
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.During the second quarter of 2021, the Company finalized its allocation of the purchase consideration to the respective fair values of assets acquired and liabilities assumed in the acquisition of Anixter. As the Company obtained additional information during the measurement period (one year from the acquisition date), it recorded adjustments to its preliminary estimates of fair value, which are presented in the table below. The net impact of these adjustments was an increase to goodwill of $13.4 million in the second quarter of 2021 and $16.4 million since the Company's initial estimate.
Gain (Loss) on Disposition of Business				$ (8,927,000)	(19,816,000)
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)		$ 165,800,000	80,000,000	437,300,000	98,400,000
Business Acquisition, Adjustments to Pro Forma Net Income (Loss)			1,300,000		5,500,000
Revenues		2,500,000,000	2,200,000,000	7,000,000,000	2,400,000,000
Business Combination, Acquisition Related Costs		$ 35,800,000	$ 14,200,000	$ 119,800,000	$ 92,100,000
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 has afforded the Company the opportunity to digitize its business and expand its services portfolio and supply chain offerings.
Business Acquisition, Description of Acquired Entity				Anixter was 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.
Anixter International \| Cash [Member]
Business Acquisition [Line Items]
Business Acquisition, Share Price \| $ / shares	$ 72.82

ACQUISITIONS (Details) $ in Thousands	9 Months Ended
ACQUISITIONS (Details) $ in Thousands	Sep. 30, 2021 USD ($)
Business Combination and Asset Acquisition [Abstract]
Proceeds from Divestiture of Businesses	$ 56,000

GOODWILL (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
GOODWILL (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Goodwill [Line Items]
Goodwill	$ 3,201,688		$ 3,201,688		$ 3,187,169
Goodwill, Foreign Currency Translation Gain (Loss)			578
Goodwill, Acquired During Period			13,941
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	2,323,583		2,323,583		2,326,919
Finite-Lived Intangible Assets, Accumulated Amortization	(345,742)		(345,742)		(261,424)
Finite-Lived Intangible Assets, Net	1,977,841		1,977,841		2,065,495
Finite-Lived Intangible Asset, Expected Amortization, Year One	33,814		33,814
Finite-Lived Intangible Asset, Expected Amortization, Year Two	92,591		92,591
Finite-Lived Intangible Asset, Expected Amortization, Year Three	83,294		83,294
Finite-Lived Intangible Asset, Expected Amortization, Year Four	80,835		80,835
Finite-Lived Intangible Asset, Expected Amortization, Year Five	77,719		77,719
Finite-Lived Intangible Asset, Expected Amortization, after Year Five	814,673		814,673
Amortization of Intangible Assets	37,100	$ 27,300	85,800	$ 45,900
Amortization of Intangible Assets	37,100	$ 27,300	85,800	$ 45,900
Finite-Lived Intangible Asset, Expected Amortization, Year Three	83,294		83,294
Finite-Lived Intangible Asset, Expected Amortization, Year Four	80,835		80,835
Finite-Lived Intangible Asset, Expected Amortization, Year Five	77,719		77,719
Finite-Lived Intangible Asset, Expected Amortization, after Year Five	814,673		814,673
Disposal Group, Including Discontinued Operation, Goodwill, Current					26,100
Trademarks [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	63,899		63,899		24,898
Finite-Lived Intangible Assets, Accumulated Amortization	(32,964)		(32,964)		(11,415)
Finite-Lived Intangible Assets, Net	30,935		$ 30,935		13,483
Disposal Group, Including Discontinued Operation, Intangible Assets					1,000
Disposal Group, Including Discontinued Operation, Intangible Assets					1,000
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	4,292		$ 4,292		4,462
Finite-Lived Intangible Assets, Accumulated Amortization	(2,916)		(2,916)		(1,384)
Finite-Lived Intangible Assets, Net	1,376		$ 1,376		3,078
Noncompete Agreements [Member] \| Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life			2 years
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	1,431,265		$ 1,431,265		1,434,554
Finite-Lived Intangible Assets, Accumulated Amortization	(287,565)		(287,565)		(227,585)
Finite-Lived Intangible Assets, Net	1,143,700		$ 1,143,700		1,206,969
Disposal Group, Including Discontinued Operation, Intangible Assets					3,300
Disposal Group, Including Discontinued Operation, Intangible Assets					3,300
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	29,212		$ 29,212		29,212
Finite-Lived Intangible Assets, Accumulated Amortization	(22,297)		(22,297)		(21,040)
Finite-Lived Intangible Assets, Net	6,915		$ 6,915		8,172
Disposal Group, Including Discontinued Operation, Intangible Assets					1,400
Disposal Group, Including Discontinued Operation, Intangible Assets					1,400
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
EES
Goodwill [Line Items]
Goodwill	856,259		$ 856,259		853,456
Goodwill, Foreign Currency Translation Gain (Loss)			1,679
Goodwill, Acquired During Period			1,124
CSS
Goodwill [Line Items]
Goodwill	1,121,914		1,121,914		1,115,500
Goodwill, Foreign Currency Translation Gain (Loss)			8,602
Goodwill, Acquired During Period			(2,188)
UBS
Goodwill [Line Items]
Goodwill	1,223,515		1,223,515		1,218,213
Goodwill, Foreign Currency Translation Gain (Loss)			4,215
Goodwill, Acquired During Period			1,087
Trademarks [Member]
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived Intangible Assets (Excluding Goodwill)	794,915		794,915		$ 833,793
Sunsetting Trademarks
Finite-Lived Intangible Assets [Line Items]
Amortization of Intangible Assets	15,100		20,200
Amortization of Intangible Assets	$ 15,100		$ 20,200

STOCK-BASED COMPENSATION AWARDS (Details) - $ / shares	3 Months Ended		9 Months Ended
STOCK-BASED COMPENSATION AWARDS (Details) - $ / shares	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	0	0	139,592	262,091
Granted, Weighted Average Fair Value (in dollars per share)	$ 0	$ 0	$ 33.19	$ 13.86
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	6,897	444,375	314,480	655,825
Granted, Weighted Average Fair Value (in dollars per share)	$ 108.76	$ 32.18	$ 77.81	$ 37.38
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	0	0	122,812	158,756
Granted, Weighted Average Fair Value (in dollars per share)	$ 0	$ 0	$ 76.76	$ 48.67

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, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number	1,617,157		1,617,157		2,161,556
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$ 63.87		$ 63.87		$ 60.48
Granted (in shares)	0	0	139,592	262,091
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price			$ 77.05
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Exercised			(671,272)
Weighted Average Exercise Price, Exercises in Period (in dollars per share)			$ 55.93
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Forfeitures			(12,719)
Weighted Average Exercise Price, Forfeitures in Period (in dollars per share)			$ 52.57
Weighted Average Remaining Contractual Term, Outstanding (in years)			5 years 8 months 12 days
Aggregate Intrinsic Value, Outstanding	$ 83,206		$ 83,206
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Number	1,247,342		1,247,342
Weighted Average Exercise Price, Exercisable (in dollars per share)	$ 64.94		$ 64.94
Weighted Average Remaining Contractual Term, Exercisable (in years)			4 years 10 months 24 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	$ 62,835		$ 62,835
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value			$ 31,000

SCHEDULE OF SHARE-BASED PAYMENT AWARD, VALUATION ASSUMPTIONS (Details) - Stock Appreciation Rights (SARs) [Member]	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate	0.80%	1.40%
Expected life (in years)	7 years	5 years
WESCO expected volatility	41.00%	30.00%

SUMMARY OF RESTRICTED STOCK UNITS (Details) - Restricted Stock Units (RSUs) [Member] - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance-based awards outstanding (in shares)	977,209		977,209		921,495
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value	$ 53.41		$ 53.41		$ 43.15
Granted (in shares)	6,897	444,375	314,480	655,825
Granted, Weighted Average Fair Value (in dollars per share)	$ 108.76	$ 32.18	$ 77.81	$ 37.38
Vested (in shares)			(228,584)
Vested in Period, Weighted Average Fair Value (in dollars per share)			$ 44.02
Forfeited (in shares)			(30,182)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value			$ 62.68

SUMMARY OF PERFORMANCE-BASED AWARDS (Details) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Unvested (in shares)	377,908		377,908		305,269
Granted (in shares)	0	0	122,812	158,756
Vested (in shares)			(22,371)
Forfeited (in shares)			(27,802)
Unvested, Weighted Average Fair Value (in dollars per share)	$ 59.35		$ 59.35		$ 52.61
Granted, Weighted Average Fair Value (in dollars per share)	$ 0	$ 0	76.76	$ 48.67
Vested in Period, Weighted Average Fair Value (in dollars per share)			62.34
Forfeited in Period, Weighted Average Fair Value (in dollars per share)			$ 59.87
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)	377,908		377,908

STOCK-BASED COMPENSATION (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended		12 Months Ended
STOCK-BASED COMPENSATION (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 9,600	$ 6,000	$ 22,784	$ 15,529
Total unrecognized compensation cost		$ 53,200		$ 53,200
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)		377,908		377,908
Forecast [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 8,000					$ 1,800	$ 17,000	$ 26,400

SCHEDULE OF EARNINGS PER SHARE, BASIC AND DILUTED (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Abstract]
Net income (loss) attributable to WESCO International, Inc.	$ 119,596	$ 119,195	$ 59,178	$ 80,678	$ (34,506)	$ 34,407	$ 297,969	$ 80,578
Weighted average common shares outstanding used in computing basic earnings per share (in shares)	50,386,000			50,043,000			50,252,000	44,873,000
Common shares issuable upon exercise of dilutive stock options (in shares)	1,677,000			444,000			1,644,000	231,000
Weighted average common shares outstanding and common share equivalents used in computing diluted earnings per share (in shares)	52,063,000			50,487,000			51,896,000	45,104,000
Earnings Per Share, Basic and Diluted [Abstract]
Basic (in dollars per share)	$ 2.09			$ 1.32			$ 5.07	$ 1.44
Diluted (in dollars per share)	$ 2.02			$ 1.31			$ 4.91	$ 1.44
Net Income (Loss) Available to Common Stockholders, Basic	$ 105,244			$ 66,167			$ 254,913	$ 64,791
Preferred Stock Dividends, Income Statement Impact	$ 14,352			$ 14,511			$ 43,056	$ 15,787

EARNINGS PER SHARE (Details) - shares	3 Months Ended	9 Months Ended
EARNINGS PER SHARE (Details) - shares	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Stock Appreciation Rights (SARs) [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	2,000,000	100,000	3,000,000

SCHEDULE OF DEBT (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Finance lease obligations	$ 17,792	$ 17,931
Total debt	4,649,756	4,975,983
Fair value adjustment to the Anixter Notes	1,131	1,650
Unamortized debt issuance costs	(65,823)	(78,850)
Short-term debt and current portion of long-term debt	(19,292)	(528,830)
Total long-term debt	4,565,772	4,369,953
Foreign Line of Credit
Debt Instrument [Line Items]
Long-term Debt	17,554	29,575
Accounts Receivable Securitization Facility
Debt Instrument [Line Items]
Long-term Debt	1,185,000	950,000
Revolving Credit Facility
Debt Instrument [Line Items]
Long-term Debt	550,000	250,000
5.375% Senior Notes due 2021
Debt Instrument [Line Items]
Long-term Debt	0	500,000
5.50% Senior Notes due 2023
Debt Instrument [Line Items]
Long-term Debt	58,636	58,636
5.375% Senior Notes due 2024
Debt Instrument [Line Items]
Long-term Debt	0	350,000
6.00% Senior Notes due 2025
Debt Instrument [Line Items]
Long-term Debt	4,173	4,173
7.125% Senior Notes due 2025
Debt Instrument [Line Items]
Long-term Debt	1,500,000	1,500,000
7.250% Senior Notes due 2028
Debt Instrument [Line Items]
Long-term Debt	1,316,601	1,315,668
Debt Instrument, Unamortized Discount	$ 8,399	$ 9,332

DEBT (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
DEBT (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2021	Dec. 31, 2020
Accounts Receivable Securitization Facility
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 1,300,000		$ 1,300,000	$ 1,200,000
Debt Instrument, Interest Rate, Stated Percentage	0.00%		0.00%	0.50%
Debt Instrument, Basis Spread on Variable Rate	1.15%	1.20%
Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.375%		5.375%
Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed			100.00%
Debt Instrument, Maturity Date			Dec. 15, 2021
5.375% Senior Notes due 2021
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 500,000		$ 500,000
5.375% Senior Notes due 2024
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 350,000		$ 350,000
Debt Instrument, Redemption Price, Percentage			101.344%
Gain (Loss) on Extinguishment of Debt, before Write off of Debt Issuance Cost			$ 4,700
Write off of Deferred Debt Issuance Cost			$ 2,200

EMPLOYEE BENEFIT PLANS EMPLOYEE BENEFIT PLANS Pension Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 4,015	$ 3,826	$ 12,082	$ 6,801
Interest cost	4,483	4,844	13,520	7,170
Expected return on plan assets	(8,691)	(8,399)	(26,139)	(12,001)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	103	(1)	311	52
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement			19	0
Net periodic benefit cost	(90)	270	(245)	2,022
Defined Benefit Plan, Service Cost	4,015	3,826	12,082	6,801
Defined Benefit Plan, Plan Assets, Contributions by Employer	2,400	2,200	8,100	4,000
UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Service cost	764	824	2,291	944
Interest cost	2,018	2,299	6,095	2,565
Expected return on plan assets	(4,414)	(4,041)	(13,241)	(4,498)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	0	0	0	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement			19	0
Net periodic benefit cost	(1,632)	(918)	(4,874)	(989)
Defined Benefit Plan, Service Cost	764	824	2,291	944
Foreign Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	3,251	3,002	9,791	5,857
Interest cost	2,465	2,545	7,425	4,605
Expected return on plan assets	(4,277)	(4,358)	(12,898)	(7,503)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	103	(1)	311	52
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement			0	0
Net periodic benefit cost	1,542	1,188	4,629	3,011
Defined Benefit Plan, Service Cost	3,251	3,002	9,791	5,857
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Other Nonoperating Gains (Losses)	$ (4,100)	$ (3,600)	(12,300)	$ (4,800)
Defined Benefit Plan, Plan Assets, Contributions by Employer			$ 10,400

Compensation Related Costs, Postemployment Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Defined Contribution Plan Disclosure [Line Items]
Postemployment Benefits, Period Expense	$ 16,400	$ 3,500	$ 49,100	$ 12,600
Service cost	4,015	3,826	12,082	6,801
Interest cost	4,483	4,844	13,520	7,170
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	8,691	8,399	26,139	12,001
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(103)	1	(311)	(52)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement			19	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	(90)	270	(245)	2,022
Increase (Decrease) in Other Operating Assets			(19,299)	26,655
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Postemployment Benefits, Period Expense	16,400	3,500	49,100	12,600
Defined Benefit Plan, Plan Assets, Contributions by Employer	2,400	2,200	8,100	4,000
Increase (Decrease) in Other Operating Assets			(19,299)	26,655
UNITED STATES
Defined Contribution Plan Disclosure [Line Items]
Service cost	764	824	2,291	944
Interest cost	2,018	2,299	6,095	2,565
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	4,414	4,041	13,241	4,498
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	0	0	0	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement			19	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	(1,632)	(918)	(4,874)	(989)
Foreign Plan
Defined Contribution Plan Disclosure [Line Items]
Service cost	3,251	3,002	9,791	5,857
Interest cost	2,465	2,545	7,425	4,605
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	4,277	4,358	12,898	7,503
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(103)	1	(311)	(52)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement			0	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	1,542	1,188	4,629	3,011
WESCO
Defined Contribution Plan Disclosure [Line Items]
Deferred Compensation Liability, Classified, Noncurrent					$ 17,300
WESCODeferredCompensationPlanMember
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred Compensation Liability, Current and Noncurrent					27,400
Deferred Compensation Liability, Current and Noncurrent					27,400
Pension Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Defined Benefit Plan, Expected Future Benefit Payment, Year One	18,100		18,100
Defined Benefit Plan, Expected Future Benefit Payment, Year One	18,100		18,100
Defined Benefit Plan, Plan Assets, Contributions by Employer			10,400
Other Nonoperating Gains (Losses)	(4,100)	(3,600)	$ (12,300)	(4,800)
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%
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%
WESCODeferredCompensationPlanMember
Defined Contribution Plan Disclosure [Line Items]
Deferred Compensation Liability, Current					10,100
Deferred Compensation Liability, Classified, Noncurrent	19,900		$ 19,900
Anixter Deferred Compensation Plan Member
Defined Contribution Plan Disclosure [Line Items]
Assets Held-in-trust					39,600
Deferred Compensation Liability, Current					45,100
Increase (Decrease) in Other Operating Assets			39,700
Deferred Compensation Arrangement with Individual, Distribution Paid			42,800
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred Compensation Arrangement with Individual, Distribution Paid			42,800
Increase (Decrease) in Other Operating Assets			$ 39,700
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	3,400	$ 1,400	$ 9,800	$ 2,300
Other Deferred Compensation Arrangements, Liability, Classified, Noncurrent	$ 20,500		$ 20,500		$ 22,800

FAIR VALUE (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative, Notional Amount	$ 200,500	$ 111,900
5.375% Senior Notes due 2024
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	0	350,000
5.375% Senior Notes due 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	0	500,000
Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	3,139,700	4,084,700
Long-term Debt	$ 2,880,500	$ 3,730,100

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References + Details

INCOME TAXES (Details)	3 Months Ended		9 Months Ended
INCOME TAXES (Details)	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Tax Contingency [Line Items]
Effective tax rate	27.20%	23.30%	22.00%	22.90%
Federal statutory rate			3.10%

INCOME TAXES Income Tax Rates (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation, Percent	27.20%	23.30%	22.00%	22.90%
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			3.10%
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Payment Arrangement, Amount			$ 7,800
Effective Income Tax Rate Reconciliation, Tax Credit, Amount			8,300
Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount			$ 4,200

Segment Reporting (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
Segment Reporting (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Segment Reporting [Abstract]
Revenues	$ 4,728,325	$ 4,141,801	$ 13,365,592	$ 8,197,154
Operating Income (Loss)	229,466	178,095	581,589	254,278
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	4,728,325	4,141,801	13,365,592	8,197,154
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Operating Income (Loss)	229,466	178,095	581,589	254,278
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	12,481,018		12,481,018		$ 11,880,214
EES
Segment Reporting [Abstract]
Operating Income (Loss)	155,210	105,508	409,062	194,643
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,982,485	1,653,726	5,626,309	3,811,498
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Operating Income (Loss)	155,210	105,508	409,062	194,643
CSS
Segment Reporting [Abstract]
Operating Income (Loss)	108,226	89,634	293,446	127,502
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,488,689	1,388,791	4,200,424	1,953,967
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Operating Income (Loss)	108,226	89,634	293,446	127,502
UBS
Segment Reporting [Abstract]
Operating Income (Loss)	108,172	74,092	289,895	167,651
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,257,151	1,099,284	3,538,859	2,431,689
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Operating Income (Loss)	108,172	74,092	289,895	167,651
Corporate Segment
Segment Reporting [Abstract]
Operating Income (Loss)	(142,142)	(91,139)	(410,814)	(235,518)
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0	0
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Operating Income (Loss)	$ (142,142)	$ (91,139)	$ (410,814)	$ (235,518)

Subsequent Events (Details) - 5.375% Senior Notes due 2024 $ in Thousands	9 Months Ended
	Sep. 30, 2021 USD ($)
Subsequent Event [Line Items]
Gain (Loss) on Extinguishment of Debt	$ 6,900
Gain (Loss) on Extinguishment of Debt, before Write off of Debt Issuance Cost	4,700
Write off of Deferred Debt Issuance Cost	2,200
Debt Instrument, Face Amount	$ 350,000
Debt Instrument, Redemption Price, Percentage	101.344%