CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Additional Capital	Retained Earnings (Deficit)	Treasury Stock	Noncontrolling Interest	Accumulated Other Comprehensive Income (Loss)	Common Class B	Common Stock
Common Stock, Value, Issued							$ 43	$ 588
Common Stock, Shares, Issued							4,339,431	58,817,781
Additional Paid in Capital, Common Stock	$ 986,020
Retained Earnings (Accumulated Deficit)	1,914,757
Treasury Stock, Value	$ (542,537)
Treasury Stock, Shares	(14,545,715)
Stockholders' Equity Attributable to Noncontrolling Interest	$ (3,269)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(391,971)
Stock Issued, Value, Stock Options Exercised, Net of Tax Benefit (Expense)				$ (4,583)				$ 3
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period				(51,401)				(243,361)
Shares Granted, Value, Share-based Payment Arrangement, after Forfeiture	14,809
APIC, Share-based Payment Arrangement, Recognition and Exercise	(407)
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation		$ (1,304)	$ 1,480					$ 0
Treasury Stock, Value, Acquired, Par Value Method		38
Treasury Stock, Value, Acquired, Cost Method	$ (100,038)
Treasury Stock, Shares, Acquired	(1,778,537)
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation								(15,380)
Net Income (Loss) Attributable to Noncontrolling Interest	$ 327				$ 327
Translation adjustment						$ 85,762
Benefit plan adjustments	6,381					(6,381)
Net Income attributable to WESCO International, Inc.	163,460
Common Stock, Value, Issued							$ 43	$ 591
Common Stock, Shares, Issued							4,339,431	59,045,762
Additional Paid in Capital, Common Stock	999,156
Retained Earnings (Accumulated Deficit)	2,079,697
Treasury Stock, Value	$ (647,158)
Treasury Stock, Shares	(16,375,653)
Stockholders' Equity Attributable to Noncontrolling Interest	$ (3,596)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(312,590)
Stock Issued, Value, Stock Options Exercised, Net of Tax Benefit (Expense)				$ (841)				$ 1
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period				(11,943)				(130,371)
Shares Granted, Value, Share-based Payment Arrangement, after Forfeiture	10,790
APIC, Share-based Payment Arrangement, Recognition and Exercise	(45)
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation		(1,254)	422					$ 0
Treasury Stock, Value, Acquired, Par Value Method		(14,981)
Treasury Stock, Value, Acquired, Cost Method	$ (110,019)
Treasury Stock, Shares, Acquired	(2,003,446)
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation								(18,437)
Net Income (Loss) Attributable to Noncontrolling Interest	$ 1,988				1,988
Translation adjustment						(99,643)
Benefit plan adjustments	(3,798)					3,798
Stockholders' equity at period end at Dec. 31, 2018	2,129,726
Net Income attributable to WESCO International, Inc.	227,343
Common Stock, Value, Issued							$ 43	$ 592
Common Stock, Shares, Issued							4,339,431	59,157,696
Additional Paid in Capital, Common Stock	993,666
Retained Earnings (Accumulated Deficit)	2,307,462
Treasury Stock, Value	$ (758,018)
Treasury Stock, Shares	(18,391,042)
Stockholders' Equity Attributable to Noncontrolling Interest	$ (5,584)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(408,435)
Stock Issued, Value, Stock Options Exercised, Net of Tax Benefit (Expense)				$ (238)				$ 1
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period				(3,730)				(198,985)
Shares Granted, Value, Share-based Payment Arrangement, after Forfeiture	19,062
APIC, Share-based Payment Arrangement, Recognition and Exercise	(84)
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation		(2,198)	$ (459)					$ 0
Treasury Stock, Value, Acquired, Par Value Method		$ 28,901
Treasury Stock, Value, Acquired, Cost Method	$ (178,901)
Treasury Stock, Shares, Acquired	(3,455,584)
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation								(48,663)
Net Income (Loss) Attributable to Noncontrolling Interest	$ 1,228				$ 1,228
Translation adjustment						49,306
Benefit plan adjustments	8,643					$ (8,643)
Stockholders' equity at period end at Dec. 31, 2019	2,258,671
Net Income attributable to WESCO International, Inc.	223,426
Common Stock, Value, Issued							$ 43	$ 593
Common Stock, Shares, Issued							4,339,431	59,308,018
Additional Paid in Capital, Common Stock	1,039,347
Retained Earnings (Accumulated Deficit)	2,530,429
Treasury Stock, Value	$ (937,157)
Treasury Stock, Shares	(21,850,356)
Stockholders' Equity Attributable to Noncontrolling Interest	$ (6,812)
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (367,772)