Debt	3 Months Ended
Mar. 31, 2018
Debt Disclosure [Abstract]
Debt	DEBT Revolving Credit Facility At March 31, 2018 and 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 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. We were in compliance with all covenants under the Credit Agreement as of March 31, 2018 and December 31, 2017. There were $180,000 and $169,643 in short-term borrowings outstanding under the Credit Agreement at March 31, 2018 and December 31, 2017, respectively. Short-term borrowings outstanding during the three months ended March 31, 2018 and 2017 ranged from a minimum of $140,000 and $112,292 to a maximum of $234,000 and $166,501, respectively. We had total letters of credit of $5,371 outstanding, of which none were issued under the Credit Agreement at both March 31, 2018 and December 31, 2017. The letters of credit are issued primarily to support certain workers' compensation insurance policies. At March 31, 2018, we had unused lines of credit under the Credit Agreement amounting to $370,000 available, compared to $380,357 at December 31, 2017. 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%). Interest expense, net was $1,411 and $797 for the three months ended March 31, 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 is expected to allow 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 March 31, 2018 and December 31, 2017. 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”). Subject to the terms and conditions set forth below, the MetLife Shelf Agreement is expected to allow us 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. No notes have been issued under the MetLife Shelf Agreement, which ranks equally with the Company’s Credit Agreement and Prudential Shelf Agreement, as of March 31, 2018 and December 31, 2017. We have agreed to 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. Each shelf agreement contains customary representations and warranties of the Company and the applicable lender, and customary events of default. 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 March 31, 2018 and December 31, 2017.

DEBT

Revolving Credit Facility

At March 31, 2018 and 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 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.

We were in compliance with all covenants under the Credit Agreement as of March 31, 2018 and December 31, 2017.

There were $180,000 and $169,643 in short-term borrowings outstanding under the Credit Agreement at March 31, 2018 and December 31, 2017, respectively.

Short-term borrowings outstanding during the three months ended March 31, 2018 and 2017 ranged from a minimum of $140,000 and $112,292 to a maximum of $234,000 and $166,501, respectively.

We had total letters of credit of $5,371 outstanding, of which none were issued under the Credit Agreement at both March 31, 2018 and December 31, 2017. The letters of credit are issued primarily to support certain workers' compensation insurance policies.

At March 31, 2018, we had unused lines of credit under the Credit Agreement amounting to $370,000 available, compared to $380,357 at December 31, 2017. 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%).

Interest expense, net was $1,411 and $797 for the three months ended March 31, 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 is expected to allow 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 March 31, 2018 and December 31, 2017.

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”). Subject to the terms and conditions set forth below, the MetLife Shelf Agreement is expected to allow us 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. No notes have been issued under the MetLife Shelf Agreement, which ranks equally with the Company’s Credit Agreement and Prudential Shelf Agreement, as of March 31, 2018 and December 31, 2017.

We have agreed to 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.

Each shelf agreement contains customary representations and warranties of the Company and the applicable lender, and customary events of default. 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 March 31, 2018 and December 31, 2017.