Debt (Narrative) (Details) - USD ($)		3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 25, 2024	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023	Jun. 24, 2024
Line of Credit Facility [Line Items]
Total debt		$ 3,700,000		$ 3,700,000		$ 4,700,000
Long-term debt		1,800,000		1,800,000		2,800,000
Short-term borrowings		0		0		0
Remaining borrowing capacity						746,400,000
Interest expense, net		500,000	$ 1,500,000	1,000,000.0	$ 2,400,000
Letters of credit outstanding		9,800,000		9,800,000		9,400,000
Minimum [Member]
Line of Credit Facility [Line Items]
Short-term borrowings		0	0	0	0
Maximum [Member]
Line of Credit Facility [Line Items]
Short-term borrowings		38,000,000.0	$ 175,000,000.0	38,000,000.0	$ 175,000,000.0
Amended Credit Agreement [Member]
Line of Credit Facility [Line Items]
Remaining borrowing capacity		746,000,000.0		$ 746,000,000.0
Credit agreement commitment fee percentage				0.40%
Letters of credit outstanding						3,600,000
Amended Credit Agreement [Member] | Graybar Canada [Member]
Line of Credit Facility [Line Items]
Letters of credit outstanding		4,000,000.0		$ 4,000,000.0
Amended Credit Agreement [Member] | Bridge Loan [Member] | Graybar Canada [Member] | Line of credit [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity						100,000,000.0
Amended Credit Agreement [Member] | Bridge Loan [Member] | United States [Member] | Graybar Canada [Member] | Line of credit [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity						75,000,000.0
Amended Credit Agreement [Member] | Bridge Loan [Member] | Canada [Member] | Graybar Canada [Member] | Line of credit [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity						20,000,000.0
Amended Credit Agreement [Member] | Revolving Credit Facility [Member] | Graybar Canada [Member] | Line of credit [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity						750,000,000.0
Accordion feature, increase limit						$ 375,000,000.0
Expiration date						Aug. 01, 2026
Debt instrument, term						5 years
Amended Credit Agreement [Member] | Letter of Credit Sub Facility [Member] | Graybar Canada [Member] | Line of credit [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity						$ 25,000,000.0
Prudential Private Placement Shelf Agreement [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity		200,000,000.0		$ 200,000,000.0
Issuance period				3 years
Notes issued face amount		0		$ 0		0
MetLife Private Placement Shelf Agreement [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 200,000,000.0						$ 150,000,000.0
Expiration date	Jun. 01, 2027
Notes issued face amount		$ 0		$ 0		$ 0