Debt	3 Months Ended
Mar. 31, 2019
Debt Disclosure [Abstract]
Debt	DEBT Revolving Credit Facility At March 31, 2019 and December 31, 2018, we, along with Graybar Canada Limited, our Canadian operating subsidiary ("Graybar Canada"), had an unsecured, five-year, $750.0 million revolving credit agreement maturing in August 2023 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 $25.0 million, a U.S. swing-line loan facility of up to $75.0 million, and a Canadian swing-line loan facility of up to $20.0 million. The Credit Agreement includes a $100.0 million sublimit (in U.S. or Canadian dollars) for borrowings by Graybar Canada. The Credit Agreement contains an accordion feature, which allows us to request increases in the aggregate borrowing commitments of up to $375.0 million. We were in compliance with all covenants under the Credit Agreement as of March 31, 2019 and December 31, 2018. There were $220.0 million and $235.0 million in short-term borrowings outstanding under the Credit Agreement at March 31, 2019 and December 31, 2018, respectively. Short-term borrowings outstanding during the three months ended March 31, 2019 and 2018 ranged from a minimum of $120.0 million and $140.0 million to a maximum of $250.0 million and $234.0 million, respectively. At March 31, 2019, we had unused lines of credit under the Credit Agreement amounting to $529.5 million available, compared to $515.0 million at December 31, 2018. 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 $1.8 million and $1.4 million for the three months ended March 31, 2019 and 2018, respectively. Private Placement Shelf Agreements We have an uncommitted $100.0 million 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 PGIM, Inc. at fixed rate terms to be agreed upon at the time of any issuance during a three-year issuance period ending in August 2020. We also have an uncommitted $100.0 million 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"). 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 issuance during a three-year period ending in August 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 March 31, 2019 and December 31, 2018. Each shelf agreement contains 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 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 Prudential Shelf Agreement and the MetLife Shelf Agreement as of March 31, 2019 and December 31, 2018. Letters of Credit We had total letters of credit of $5.6 million outstanding at March 31, 2019, of which $0.5 million were issued under the Credit Agreement. We had total letters of credit of $5.6 million outstanding at December 31, 2018, of which none were issued under the Credit Agreement. The letters of credit are issued primarily to support certain workers' compensation insurance policies.

DEBT

Revolving Credit Facility

At March 31, 2019 and December 31, 2018, we, along with Graybar Canada Limited, our Canadian operating subsidiary ("Graybar Canada"), had an unsecured, five-year, $750.0 million revolving credit agreement maturing in August 2023 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 $25.0 million, a U.S. swing-line loan facility of up to $75.0 million, and a Canadian swing-line loan facility of up to $20.0 million. The Credit Agreement includes a $100.0 million sublimit (in U.S. or Canadian dollars) for borrowings by Graybar Canada. The Credit Agreement contains an accordion feature, which allows us to request increases in the aggregate borrowing commitments of up to $375.0 million.

We were in compliance with all covenants under the Credit Agreement as of March 31, 2019 and December 31, 2018.

There were $220.0 million and $235.0 million in short-term borrowings outstanding under the Credit Agreement at March 31, 2019 and December 31, 2018, respectively.

Short-term borrowings outstanding during the three months ended March 31, 2019 and 2018 ranged from a minimum of $120.0 million and $140.0 million to a maximum of $250.0 million and $234.0 million, respectively.

At March 31, 2019, we had unused lines of credit under the Credit Agreement amounting to $529.5 million available, compared to $515.0 million at December 31, 2018. 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 $1.8 million and $1.4 million for the three months ended March 31, 2019 and 2018, respectively.

Private Placement Shelf Agreements

We have an uncommitted $100.0 million 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 PGIM, Inc. at fixed rate terms to be agreed upon at the time of any issuance during a three-year issuance period ending in August 2020. We also have an uncommitted $100.0 million 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"). 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 issuance during a three-year period ending in August 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 March 31, 2019 and December 31, 2018.

Each shelf agreement contains 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 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 Prudential Shelf Agreement and the MetLife Shelf Agreement as of March 31, 2019 and December 31, 2018.

Letters of Credit

We had total letters of credit of $5.6 million outstanding at March 31, 2019, of which $0.5 million were issued under the Credit Agreement. We had total letters of credit of $5.6 million outstanding at December 31, 2018, of which none were issued under the Credit Agreement. The letters of credit are issued primarily to support certain workers' compensation insurance policies.