Compensation Related Costs, Postemployment Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Defined Contribution Plan Disclosure [Line Items]
Postemployment Benefits, Period Expense	$ 16,100	$ 3,400	$ 32,700	$ 9,100
Service cost	4,079	1,668	8,067	2,977
Interest cost	4,455	1,288	9,037	2,325
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	8,692	1,988	17,447	3,603
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(106)	(26)	(207)	(53)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	19	0	19	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	(71)	994	(155)	1,752
Increase (Decrease) in Other Operating Assets			14,291	28,078
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Postemployment Benefits, Period Expense	16,100	3,400	32,700	9,100
Defined Benefit Plan, Plan Assets, Contributions by Employer	3,100	800	5,700	1,800
Increase (Decrease) in Other Operating Assets			14,291	28,078
UNITED STATES
Defined Contribution Plan Disclosure [Line Items]
Service cost	763	121	1,527	121
Interest cost	1,941	265	4,077	265
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	4,327	457	8,827	457
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	19	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	(1,642)	(71)	(3,242)	(71)
Foreign Plan
Defined Contribution Plan Disclosure [Line Items]
Service cost	3,316	1,547	6,540	2,856
Interest cost	2,514	1,023	4,960	2,060
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	4,365	1,531	8,620	3,146
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(106)	(26)	(207)	(53)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	0	0	0	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	1,571	1,065	3,087	1,823
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)	(4,200)	(700)	$ (8,200)	(1,200)
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	19,300		$ 19,300
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	600	$ 900	$ 6,300	$ 900
Other Deferred Compensation Arrangements, Liability, Classified, Noncurrent	$ 18,200		$ 18,200		$ 22,800