Debt	9 Months Ended
Sep. 30, 2018
Debt Disclosure [Abstract]
Debt	DEBT Revolving Credit Facility At December 31, 2017, 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 included 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 included a $100,000 sublimit (in U.S. or Canadian dollars) for borrowings by Graybar Canada and contained an accordion feature, which allowed us to request increases to the aggregate borrowing commitments of up to $300,000. On August 10, 2018, we, along with Graybar Canada, amended and extended the Credit Agreement (the “Amended Credit Agreement”), to, among other things, increase the availability to $750,000, which includes a combined letter of credit sub-facility of up to $25,000, a U.S. swing-line loan facility of up to $75,000, and a Canadian swing-line loan facility of up to $20,000, pursuant to the terms and conditions of a Third Amendment to Credit Agreement, by and among Graybar, as parent borrower, Graybar Canada Limited, as a borrower, the lenders party thereto, Bank of America, N.A. as Domestic Administrative Agent, Domestic Swing Line Lender and Domestic L/C Issuer and Bank of America, N.A., acting through its Canada Branch, as Canadian Administrative Agent, Canadian Swing Line Lender and Canadian L/C Issuer. The Amended Credit Agreement includes a $100,000 sublimit (in U.S. or Canadian dollars) for borrowings by Graybar Canada. The Amended Credit Agreement contains an accordion feature, which allows us to request increases in the aggregate borrowing commitments of up to $375,000. Interest on our borrowings under the Amended Credit Agreement will be based on, at the borrower’s election, either (A) (i) the base rate (as defined in the agreement) plus a margin ranging from 0.00% to 0.60%, or (ii) LIBOR (in the case of Graybar as borrower) plus a margin ranging from 1.00% to 1.60% or (B) (i) the base rate (as defined in the agreement) plus a margin ranging from 0.00% to 0.60% or (ii) CDOR (in the case of Graybar Canada as borrower), plus a margin ranging from 1.00% to 1.60%, as determined by the pricing grid set forth in the Amended Credit Agreement, subject to adjustment based upon the consolidated leverage ratio. In connection with such a borrowing, the applicable borrower will also select the term of the loan, up to six months, or automatically renew with the consent of the lenders. Swing line loans, which are daily loans, will bear interest at a rate based on, at the borrower’s election, either (i) the base rate or (ii) the daily floating Eurodollar rate (or CDOR, in the case of Graybar Canada). In addition to interest payments, there are certain fees and obligations associated with borrowings, swing-line loans, letters of credit and other administrative matters. The Amended Credit Agreement matures in August 2023. Borrowings of Graybar Canada may be in U.S. dollars or Canadian dollars. The obligations of Graybar Canada are secured by the guaranty of Graybar and any material domestic subsidiaries of Graybar (as defined). Under no circumstances will Graybar Canada use its borrowings to benefit Graybar or its operations, including without limitation to repay any of Graybar’s obligations under the facility. The Amended Credit Agreement provides for a quarterly commitment fee ranging from 0.25% to 0.40% per annum, subject to adjustment based upon the consolidated leverage ratio for a fiscal quarter, and letter of credit fees ranging from 1.00% to 1.60% per annum payable quarterly, subject to such adjustment. Availability under the Amended Credit Agreement is subject to the accuracy of representations and warranties and absence of a default and, in the case of Canadian borrowings denominated in Canadian dollars, the absence of a material adverse change in the national or international financial markets that would make it impracticable to lend Canadian dollars. The Amended Credit Agreement also provides for customary events of default, including a failure to pay principal, interest or fees when due, failure to comply with covenants, the fact that any representation or warranty made by any of the credit parties is materially incorrect, failure to comply with covenants, the occurrence of an event of default under certain other indebtedness by 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 any of the credit parties (subject to certain permitted transactions as described in the Amended Credit Agreement). Upon the occurrence of an event of default, the commitments of the lenders may be terminated and all outstanding obligations of the credit parties under the Amended Credit Agreement may be declared immediately due and payable. The Amended Credit Agreement contains updated affirmative and negative covenants customary for credit facilities of this type, including limitations on us and our subsidiaries with respect to indebtedness (with specified, limited exceptions), 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, including payments under senior notes), as well as securitizations, factoring transactions, and transactions with sanctioned parties or in violation of certain US or Canadian anti-corruption laws. There are also maximum leverage ratio and minimum interest coverage ratio financial covenants to which we will be subject to during the term of the Amended Credit Agreement. We were in compliance with all these covenants under the applicable credit agreement as of September 30, 2018 and December 31, 2017. There were $246,000 and $169,643 in short-term borrowings outstanding under the applicable credit agreement at September 30, 2018 and December 31, 2017, respectively. Short-term borrowings outstanding during the nine months ended September 30, 2018 and 2017 ranged from a minimum of $140,000 and $112,292 to a maximum of $249,000 and $229,782, respectively. At September 30, 2018, we had unused lines of credit under the applicable credit agreement amounting to $504,000 available, compared to $380,357 at December 31, 2017. Interest expense, net was $1,878 and $1,217 for the three months ended September 30, 2018 and 2017, respectively. Interest expense, net was $4,988 and $3,082 for the nine months ended September 30, 2018 and 2017, respectively. Private Placement Shelf Agreements We have an uncommitted $100,000 private placement shelf agreement with PGIM, Inc. (the "Prudential Shelf Agreement") which expires in August 2020. We also have 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"). On August 10, 2018, we amended each of these uncommitted private placement shelf agreements to conform to the above-discussed specified changes in the Amended Credit Agreement. We also extended the notes issuance period under the MetLife Shelf Agreement from September 2019 to August 10, 2021. We remain obligated under a most favored lender clause which is designed to ensure that any notes 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. No notes have been issued under either the Prudential Shelf Agreement or the MetLife Shelf Agreement as of September 30, 2018 and December 31, 2017. Each amended shelf agreement contains updated representations and warranties of the Company and the applicable lender, customary events of default and affirmative and negative covenants, customary for agreements of this type. These covenants are substantially similar to those contained in the Amended Credit Agreement, subject to a number of important exceptions and qualifications set forth in the applicable shelf 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. We were in compliance with all covenants under the shelf agreements as of September 30, 2018 and December 31, 2017. Letters of Credit We had total letters of credit of $5,621 and $5,371 outstanding, of which none were issued under the applicable credit agreement at September 30, 2018 and December 31, 2017, respectively. The letters of credit are issued primarily to support certain workers' compensation insurance policies.

DEBT

Revolving Credit Facility

At December 31, 2017, 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 included 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 included a $100,000 sublimit (in U.S. or Canadian dollars) for borrowings by Graybar Canada and contained an accordion feature, which allowed us to request increases to the aggregate borrowing commitments of up to $300,000.

On August 10, 2018, we, along with Graybar Canada, amended and extended the Credit Agreement (the “Amended Credit Agreement”), to, among other things, increase the availability to $750,000, which includes a combined letter of credit sub-facility of up to $25,000, a U.S. swing-line loan facility of up to $75,000, and a Canadian swing-line loan facility of up to $20,000, pursuant to the terms and conditions of a Third Amendment to Credit Agreement, by and among Graybar, as parent borrower, Graybar Canada Limited, as a borrower, the lenders party thereto, Bank of America, N.A. as Domestic Administrative Agent, Domestic Swing Line Lender and Domestic L/C Issuer and Bank of America, N.A., acting through its Canada Branch, as Canadian Administrative Agent, Canadian Swing Line Lender and Canadian L/C Issuer. The Amended Credit Agreement includes a $100,000 sublimit (in U.S. or Canadian dollars) for borrowings by Graybar Canada. The Amended Credit Agreement contains an accordion feature, which allows us to request increases in the aggregate borrowing commitments of up to $375,000.

Interest on our borrowings under the Amended Credit Agreement will be based on, at the borrower’s election, either (A) (i) the base rate (as defined in the agreement) plus a margin ranging from 0.00% to 0.60%, or (ii) LIBOR (in the case of Graybar as borrower) plus a margin ranging from 1.00% to 1.60% or (B) (i) the base rate (as defined in the agreement) plus a margin ranging from 0.00% to 0.60% or (ii) CDOR (in the case of Graybar Canada as borrower), plus a margin ranging from 1.00% to 1.60%, as determined by the pricing grid set forth in the Amended Credit Agreement, subject to adjustment based upon the consolidated leverage ratio. In connection with such a borrowing, the applicable borrower will also select the term of the loan, up to six months, or automatically renew with the consent of the lenders. Swing line loans, which are daily loans, will bear interest at a rate based on, at the borrower’s election, either (i) the base rate or (ii) the daily floating Eurodollar rate (or CDOR, in the case of Graybar Canada). In addition to interest payments, there are certain fees and obligations associated with borrowings, swing-line loans, letters of credit and other administrative matters.

The Amended Credit Agreement matures in August 2023. Borrowings of Graybar Canada may be in U.S. dollars or Canadian dollars. The obligations of Graybar Canada are secured by the guaranty of Graybar and any material domestic subsidiaries of Graybar (as defined). Under no circumstances will Graybar Canada use its borrowings to benefit Graybar or its operations, including without limitation to repay any of Graybar’s obligations under the facility.

The Amended Credit Agreement provides for a quarterly commitment fee ranging from 0.25% to 0.40% per annum, subject to adjustment based upon the consolidated leverage ratio for a fiscal quarter, and letter of credit fees ranging from 1.00% to 1.60% per annum payable quarterly, subject to such adjustment. Availability under the Amended Credit Agreement is subject to the accuracy of representations and warranties and absence of a default and, in the case of Canadian borrowings denominated in Canadian dollars, the absence of a material adverse change in the national or international financial markets that would make it impracticable to lend Canadian dollars.

The Amended Credit Agreement also provides for customary events of default, including a failure to pay principal, interest or fees when due, failure to comply with covenants, the fact that any representation or warranty made by any of the credit parties is materially incorrect, failure to comply with covenants, the occurrence of an event of default under certain other indebtedness by 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 any of the credit parties (subject to certain permitted transactions as described in the Amended Credit Agreement). Upon the occurrence of an event of default, the commitments of the lenders may be terminated and all outstanding obligations of the credit parties under the Amended Credit Agreement may be declared immediately due and payable.

The Amended Credit Agreement contains updated affirmative and negative covenants customary for credit facilities of this type, including limitations on us and our subsidiaries with respect to indebtedness (with specified, limited exceptions), 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, including payments under senior notes), as well as securitizations, factoring transactions, and transactions with sanctioned parties or in violation of certain US or Canadian anti-corruption laws. There are also maximum leverage ratio and minimum interest coverage ratio financial covenants to which we will be subject to during the term of the Amended Credit Agreement. We were in compliance with all these covenants under the applicable credit agreement as of September 30, 2018 and December 31, 2017.

There were $246,000 and $169,643 in short-term borrowings outstanding under the applicable credit agreement at September 30, 2018 and December 31, 2017, respectively.

Short-term borrowings outstanding during the nine months ended September 30, 2018 and 2017 ranged from a minimum of $140,000 and $112,292 to a maximum of $249,000 and $229,782, respectively.

At September 30, 2018, we had unused lines of credit under the applicable credit agreement amounting to $504,000 available, compared to $380,357 at December 31, 2017.

Interest expense, net was $1,878 and $1,217 for the three months ended September 30, 2018 and 2017, respectively. Interest expense, net was $4,988 and $3,082 for the nine months ended September 30, 2018 and 2017, respectively.

Private Placement Shelf Agreements

We have an uncommitted $100,000 private placement shelf agreement with PGIM, Inc. (the "Prudential Shelf Agreement") which expires in August 2020. We also have 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"). On August 10, 2018, we amended each of these uncommitted private placement shelf agreements to conform to the above-discussed specified changes in the Amended Credit Agreement. We also extended the notes issuance period under the MetLife Shelf Agreement from September 2019 to August 10, 2021.

We remain obligated under a most favored lender clause which is designed to ensure that any notes 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.

No notes have been issued under either the Prudential Shelf Agreement or the MetLife Shelf Agreement as of September 30, 2018 and December 31, 2017.

Each amended shelf agreement contains updated representations and warranties of the Company and the applicable lender, customary events of default and affirmative and negative covenants, customary for agreements of this type. These covenants are substantially similar to those contained in the Amended Credit Agreement, subject to a number of important exceptions and qualifications set forth in the applicable shelf 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.

We were in compliance with all covenants under the shelf agreements as of September 30, 2018 and December 31, 2017.

Letters of Credit

We had total letters of credit of $5,621 and $5,371 outstanding, of which none were issued under the applicable credit agreement at September 30, 2018 and December 31, 2017, respectively. The letters of credit are issued primarily to support certain workers' compensation insurance policies.