Debt	9 Months Ended
Sep. 30, 2017
Debt Disclosure [Abstract]
Debt	DEBT Revolving Credit Facility At September 30, 2017 and December 31, 2016, we along with Graybar Canada Limited, our Canadian operating subsidiary (“Graybar Canada”), had an unsecured, five-year, $550,000 revolving credit agreement maturing in June 2019 with Bank of America, N.A. and the other lenders named therein (the "Credit Agreement"), which includes a combined letter of credit sub-facility of up to $50,000, a U.S. swing line loan facility of up to $50,000, and a Canadian swing line loan facility of up to $20,000. The Credit Agreement includes a $100,000 sublimit (in U.S. or Canadian dollars) for borrowings by Graybar Canada and contains an accordion feature, which allows us to request increases to the aggregate borrowing commitments of up to $300,000. The Credit Agreement contains customary affirmative and negative covenants for credit facilities of this type, including limitations on us and our subsidiaries with respect to indebtedness, liens, changes in the nature of our business, investments, mergers and acquisitions, issuance of equity securities, dispositions of assets and dissolution of certain subsidiaries, transactions with affiliates, restricted payments (subject to incurrence tests, with certain exceptions), as well as securitizations, factoring transactions, and transactions with sanctioned parties or in violation of certain U.S. or Canadian anti-corruption laws. There are also maximum leverage ratio and minimum interest coverage ratio financial covenants that we are subject to during the term of the Credit Agreement. We were in compliance with all these covenants as of September 30, 2017 and December 31, 2016. There were $216,604 and $140,465 in short-term borrowings outstanding under the Credit Agreement at September 30, 2017 and December 31, 2016, respectively. Short-term borrowings outstanding during the nine months ended September 30, 2017 and 2016 ranged from a minimum of $112,292 and $105,014 to a maximum of $229,782 and $311,506, respectively. We had total letters of credit of $5,371 and $5,244 outstanding, of which none were issued under the Credit Agreement at September 30, 2017 and December 31, 2016. The letters of credit are issued primarily to support certain workers' compensation insurance policies. At September 30, 2017, we had unused lines of credit under the Credit Agreement amounting to $333,396 available, compared to $409,535 at December 31, 2016. These lines are available to meet our short-term cash requirements and are subject to annual fees of up to 40 basis points (0.40%). Private Placement Shelf Agreements On August 2, 2017, we amended our uncommitted $100,000 private placement shelf agreement with PGIM, Inc., formerly known as Prudential Investment Management, Inc. (the "Prudential Shelf Agreement"). The Prudential Shelf Agreement allows us to issue senior promissory notes to affiliates of Prudential at fixed rate terms to be agreed upon at the time of any issuance during a three year issuance period ending in August 2020. No notes had been issued under the Prudential Shelf Agreement as of September 30, 2017 and December 31, 2016. On September 22, 2016, we entered into an uncommitted $100,000 private placement shelf agreement (the “MetLife Shelf Agreement”) with Metropolitan Life Insurance Company and MetLife Investment Advisors, LLC and each other affiliate of MetLife that becomes a party to the agreement (collectively, “MetLife”). Subject to the terms and conditions set forth below, the MetLife Shelf Agreement is expected to allow the Company to issue senior promissory notes to MetLife at fixed or floating rate economic terms to be agreed upon at the time of any issuance during a three-year issuance period ending in September 2019. Floating rate note interest rates will be based on London Interbank Offered Rate ("LIBOR") plus a spread. No notes have been issued under the MetLife Shelf Agreement, which ranks equally with the Company’s Credit Agreement and Prudential Shelf Agreement. No notes had been issued under the MetLife Shelf Agreement as of September 30, 2017 and December 31, 2016. Under these shelf agreements, the term of each note issuance will be selected by us and will not exceed 12 years and will have such other particular terms as shall be set forth, in the case of any series of notes, in the Confirmation of Acceptance with respect to such series. Any notes issued under the Prudential Shelf Agreement or under the MetLife Shelf Agreement will be guaranteed by our material domestic subsidiaries, if any, as described in the Prudential Shelf Agreement and the MetLife Shelf Agreement. Any future proceeds of any issuance under the facilities will be used for general corporate purposes, including working capital and capital expenditures, to refinance existing indebtedness and/or to fund potential acquisitions. Each shelf agreement contains customary representations and warranties of the Company and the applicable lender. Each shelf agreement also contains customary events of default, including: a failure to pay principal, interest or fees when due; a failure to comply with covenants; the fact that any representation or warranty made by any of the credit parties is incorrect when given; the occurrence of an event of default under the Credit Agreement or certain other indebtedness of us and our subsidiaries; the commencement of certain insolvency or receivership events affecting any of the credit parties; certain actions under ERISA; and the occurrence of a change in control of Graybar (subject to certain permitted transactions as described in the Credit Agreement). All outstanding obligations of Graybar under one or both of these agreements may be declared immediately due and payable upon the occurrence of an event of default. Each shelf agreement contains customary affirmative and negative covenants for facilities of this type, including limitations on us and our subsidiaries with respect to indebtedness, liens, changes in the nature of our business, investments, mergers and acquisitions, issuance of equity securities, dispositions of assets and dissolution of certain subsidiaries, transactions with affiliates, restricted payments (subject to incurrence tests, with certain exceptions), as well as securitizations, factoring transactions, and transactions with sanctioned parties or in violation of certain U.S. or Canadian anti-terrorism laws. There are also maximum leverage ratio and minimum interest coverage ratio financial covenants that we are subject to during the term of the shelf agreements. We were in compliance with all covenants as of September 30, 2017 and December 31, 2016. In addition, we have agreed to a most favored lender clause which is designed to ensure that any notes issued in the future under the Prudential Shelf Agreement and MetLife Shelf Agreement will continue to be of equal ranking with indebtedness under our Credit Agreement.

DEBT

Revolving Credit Facility

At September 30, 2017 and December 31, 2016, we along with Graybar Canada Limited, our Canadian operating subsidiary (“Graybar Canada”), had an unsecured, five-year, $550,000 revolving credit agreement maturing in June 2019 with Bank of America, N.A. and the other lenders named therein (the "Credit Agreement"), which includes a combined letter of credit sub-facility of up to $50,000, a U.S. swing line loan facility of up to $50,000, and a Canadian swing line loan facility of up to $20,000. The Credit Agreement includes a $100,000 sublimit (in U.S. or Canadian dollars) for borrowings by Graybar Canada and contains an accordion feature, which allows us to request increases to the aggregate borrowing commitments of up to $300,000.

The Credit Agreement contains customary affirmative and negative covenants for credit facilities of this type, including limitations on us and our subsidiaries with respect to indebtedness, liens, changes in the nature of our business, investments, mergers and acquisitions, issuance of equity securities, dispositions of assets and dissolution of certain subsidiaries, transactions with affiliates, restricted payments (subject to incurrence tests, with certain exceptions), as well as securitizations, factoring transactions, and transactions with sanctioned parties or in violation of certain U.S. or Canadian anti-corruption laws. There are also maximum leverage ratio and minimum interest coverage ratio financial covenants that we are subject to during the term of the Credit Agreement. We were in compliance with all these covenants as of September 30, 2017 and December 31, 2016.

There were $216,604 and $140,465 in short-term borrowings outstanding under the Credit Agreement at September 30, 2017 and December 31, 2016, respectively.

Short-term borrowings outstanding during the nine months ended September 30, 2017 and 2016 ranged from a minimum of $112,292 and $105,014 to a maximum of $229,782 and $311,506, respectively.

We had total letters of credit of $5,371 and $5,244 outstanding, of which none were issued under the Credit Agreement at September 30, 2017 and December 31, 2016. The letters of credit are issued primarily to support certain workers' compensation insurance policies.

At September 30, 2017, we had unused lines of credit under the Credit Agreement amounting to $333,396 available, compared to $409,535 at December 31, 2016. These lines are available to meet our short-term cash requirements and are subject to annual fees of up to 40 basis points (0.40%).

Private Placement Shelf Agreements

On August 2, 2017, we amended our uncommitted $100,000 private placement shelf agreement with PGIM, Inc., formerly known as Prudential Investment Management, Inc. (the "Prudential Shelf Agreement"). The Prudential Shelf Agreement allows us to issue senior promissory notes to affiliates of Prudential at fixed rate terms to be agreed upon at the time of any issuance during a three year issuance period ending in August 2020. No notes had been issued under the Prudential Shelf Agreement as of September 30, 2017 and December 31, 2016.

On September 22, 2016, we entered into an uncommitted $100,000 private placement shelf agreement (the “MetLife Shelf Agreement”) with Metropolitan Life Insurance Company and MetLife Investment Advisors, LLC and each other affiliate of MetLife that becomes a party to the agreement (collectively, “MetLife”). Subject to the terms and conditions set forth below, the MetLife Shelf Agreement is expected to allow the Company to issue senior promissory notes to MetLife at fixed or floating rate economic terms to be agreed upon at the time of any issuance during a three-year issuance period ending in September 2019. Floating rate note interest rates will be based on London Interbank Offered Rate ("LIBOR") plus a spread. No notes have been issued under the MetLife Shelf Agreement, which ranks equally with the Company’s Credit Agreement and Prudential Shelf Agreement. No notes had been issued under the MetLife Shelf Agreement as of September 30, 2017 and December 31, 2016.

Under these shelf agreements, the term of each note issuance will be selected by us and will not exceed 12 years and will have such other particular terms as shall be set forth, in the case of any series of notes, in the Confirmation of Acceptance with respect to such series. Any notes issued under the Prudential Shelf Agreement or under the MetLife Shelf Agreement will be guaranteed by our material domestic subsidiaries, if any, as described in the Prudential Shelf Agreement and the MetLife Shelf Agreement. Any future proceeds of any issuance under the facilities will be used for general corporate purposes, including working capital and capital expenditures, to refinance existing indebtedness and/or to fund potential acquisitions.

Each shelf agreement contains customary representations and warranties of the Company and the applicable lender. Each shelf agreement also contains customary events of default, including: a failure to pay principal, interest or fees when due; a failure to comply with covenants; the fact that any representation or warranty made by any of the credit parties is incorrect when given; the occurrence of an event of default under the Credit Agreement or certain other indebtedness of us and our subsidiaries; the commencement of certain insolvency or receivership events affecting any of the credit parties; certain actions under ERISA; and the occurrence of a change in control of Graybar (subject to certain permitted transactions as described in the Credit Agreement). All outstanding obligations of Graybar under one or both of these agreements may be declared immediately due and payable upon the occurrence of an event of default.

Each shelf agreement contains customary affirmative and negative covenants for facilities of this type, including limitations on us and our subsidiaries with respect to indebtedness, liens, changes in the nature of our business, investments, mergers and acquisitions, issuance of equity securities, dispositions of assets and dissolution of certain subsidiaries, transactions with affiliates, restricted payments (subject to incurrence tests, with certain exceptions), as well as securitizations, factoring transactions, and transactions with sanctioned parties or in violation of certain U.S. or Canadian anti-terrorism laws. There are also maximum leverage ratio and minimum interest coverage ratio financial covenants that we are subject to during the term of the shelf agreements. We were in compliance with all covenants as of September 30, 2017 and December 31, 2016.

In addition, we have agreed to a most favored lender clause which is designed to ensure that any notes issued in the future under the Prudential Shelf Agreement and MetLife Shelf Agreement will continue to be of equal ranking with indebtedness under our Credit Agreement.