Debt (Narrative) (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Jul. 20, 2023	Jul. 19, 2023
Line of Credit Facility [Line Items]
Short-term borrowings	$ 102,000,000.0		$ 102,000,000.0		$ 31,600,000
Interest expense, net	1,500,000	$ 800,000	3,900,000	$ 2,300,000
Letters of credit outstanding	8,100,000		8,100,000		7,800,000
Minimum
Line of Credit Facility [Line Items]
Short-term borrowings	0	0	0	0
Maximum
Line of Credit Facility [Line Items]
Short-term borrowings	232,000,000.0	$ 173,100,000	232,000,000.0	$ 173,100,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Short-term borrowings					30,000,000.0
Amended Credit Agreement
Line of Credit Facility [Line Items]
Remaining borrowing capacity	645,700,000		$ 645,700,000		718,100,000
Credit agreement commitment fee percentage			0.40%
Letters of credit outstanding	2,300,000		$ 2,300,000		1,900,000
Prudential Private Placement Shelf Agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity						$ 200,000,000.0	$ 100,000,000.0
Issuance period			3 years
MetLife Private Placement Shelf Agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity	150,000,000.0		$ 150,000,000.0
Debt maturity date			Jun. 01, 2024
Issuance period			3 years
Prudential Shelf Agreement Or MetLife Shelf Agreement
Line of Credit Facility [Line Items]
Notes issued face amount	$ 0		$ 0		0
Line of credit | Amended Credit Agreement | Revolving Credit Facility
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
Line of credit | Amended Credit Agreement | Letter of Credit Sub-Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity					$ 25,000,000.0
Line of credit | Amended Credit Agreement | Bridge Loan | Graybar Canada
Line of Credit Facility [Line Items]
Maximum borrowing capacity					100,000,000.0
Line of credit | Amended Credit Agreement | Bridge Loan | UNITED STATES
Line of Credit Facility [Line Items]
Maximum borrowing capacity					75,000,000.0
Line of credit | Amended Credit Agreement | Bridge Loan | CANADA
Line of Credit Facility [Line Items]
Maximum borrowing capacity					$ 20,000,000.0