Summary Of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2020
Summary Of Significant Accounting Policies [Abstract]
Summary Of Significant Accounting Policies	2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Our accounting policies conform to generally accepted accounting principles in the U.S. ("GAAP”) and are applied on a consistent basis among all years presented. Significant accounting policies are described below. Basis of Presentation The unaudited condensed consolidated financial statements included herein have been prepared by Graybar pursuant to the rules and regulations of the U.S. Securities and Exchange Commission (the “Commission”) applicable to interim financial reporting.  Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations, although we believe that our disclosures are adequate to make the information presented not misleading.  The preparation of financial statements in accordance with GAAP requires the use of estimates and assumptions that affect reported amounts.  Our condensed consolidated financial statements include amounts that are based on management’s best estimates and judgments.  Actual results could differ from those estimates.  These condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto as of and for the year ended December 31, 2019, included in our latest Annual Report on Form 10-K. In the opinion of management, this quarterly report includes all adjustments, consisting of normal recurring accruals and adjustments, necessary for the fair presentation of the condensed consolidated financial statements presented.  Results for interim periods are not necessarily indicative of results to be expected for the full year. Principles of Consolidation The condensed consolidated financial statements include the accounts of Graybar and its subsidiary companies.  All material intercompany balances and transactions have been eliminated.  The ownership interests that are held by owners other than the Company in subsidiaries consolidated by the Company are accounted for and reported as noncontrolling interests. Estimates The preparation of financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses, and the disclosure of contingent assets and liabilities.  Actual results could differ from these estimates. Revenue Recognition Sales revenue is recognized when performance obligations are satisfied, which is typically upon delivery of the product to the customer.  Sometimes product is purchased from the manufacturer and drop-shipped to the customer. We generally take control of the goods when shipped by the manufacturer and then recognize revenue when control of the product transfers to the customer. Revenues recognized are primarily for product sales, but may also include freight and handling charges. Our standard warehouse shipping terms are FOB shipping point, under which control passes to the customer at the time of shipment. We also earn revenue for professional services, general contracting services, and storage services. Such service revenue represented less than 1% of net sales for the nine months ended September 30, 2020 and 2019. Revenue is reported net of all taxes, primarily sales tax, assessed by governmental authorities as a result of revenue-producing transactions. Outgoing Freight Expenses We record 95% of outgoing freight expenses as a component of selling, general and administrative expenses. Cash and Cash Equivalents We account for cash on hand, deposits in banks, and other short-term, highly liquid investments with an original maturity of three months or less as cash and cash equivalents. Allowance for Credit Losses We perform ongoing credit evaluations of our customers, and a significant portion of our trade receivables is secured by mechanic’s lien or payment bond rights.  We maintain allowances to reflect the expected uncollectability of trade receivables based on past collection history pooled on the aging of the receivables, specific risks identified in the receivables portfolio based on current conditions, and expected future economic conditions when necessary.  Although actual credit losses have historically been within management’s expectations, additional allowances may be required if the financial condition of our customers were to deteriorate. Merchandise Inventory Our inventory, comprised entirely of finished goods, is stated at the lower of cost (generally determined using the last-in, first-out (“LIFO”) cost method) or market.  Inventories valued using the LIFO method comprised 89% of the total inventories at September 30, 2020 and 91% at September 30, 2019. LIFO accounting is a method of accounting that, compared with other inventory accounting methods, generally provides better matching of current costs with current sales. We make provisions for obsolete or excess inventories as necessary to reflect reductions in inventory value. Vendor Allowances Our agreements with many of our suppliers provide for us to earn volume incentives based on purchases during the agreement period.  Based on the provisions of our vendor agreements, we develop vendor accrual rates by estimating our performance under the agreements and the amounts that will be earned. We perform analyses and review historical trends to ensure the deferred amounts earned are appropriately recorded. Certain vendor agreements contain purchase volume incentives that provide for increased funding when graduated purchase volumes are met. Amounts accrued throughout the year are based on estimates of future activity levels, and could be materially impacted if actual purchase volumes differ. Changes in the estimated amount of incentives are treated as changes in estimate and are recognized in earnings in the period in which the change in estimate occurs.  In the event that the operating performance of our suppliers were to decline, however, there can be no assurance that amounts earned would be paid or that the volume incentives would continue to be included in future agreements. Property and Depreciation Property, plant and equipment are recorded at cost. Depreciation is expensed on a straight-line basis over the estimated useful lives of the related assets. Interest costs incurred to finance expenditures for major long-term construction projects are capitalized as part of the asset's historical cost and included in property, plant and equipment, then depreciated over the useful life of the asset. Leasehold improvements are amortized over the term of the lease or the estimated useful life of the improvement, whichever is shorter. Expenditures for maintenance and repairs are charged to expense when incurred, while the costs of significant improvements, which extend the useful life of the underlying asset, are capitalized. Credit Risk Financial instruments that potentially expose us to concentrations of credit risk consist primarily of trade receivables.  We perform ongoing credit evaluations of our customers, and a significant portion of our trade receivables are secured by mechanic’s lien or payment bond rights.  We maintain allowances for potential credit losses, and such losses historically have been within management’s expectations. Fair Value We endeavor to utilize the best available information in measuring fair value.  GAAP has established a fair value hierarchy, which prioritizes the inputs used in measuring fair value.  The tiers in the hierarchy include:  Level 1, defined as observable inputs such as quoted prices in active markets; Level 2, defined as inputs other than quoted prices in active markets that are either directly or indirectly observable; and Level 3, defined as unobservable inputs for which little or no market data exists, therefore requiring an entity to develop its own data inputs and assumptions.  We have used fair value measurements to value our pension plan assets. Foreign Currency Exchange Rate The functional currency for our Canadian subsidiary is the Canadian dollar.  Accordingly, its balance sheet amounts are translated at the exchange rates in effect at the end of each reporting period and its statements of income amounts are translated at the average rates of exchange prevailing during the current period.  Currency translation adjustments are included in accumulated other comprehensive loss. Goodwill Our goodwill is not amortized, but rather tested annually for impairment.  Goodwill is reviewed annually in the fourth quarter and when circumstances or other events might indicate that impairment may have occurred.  We first perform a qualitative assessment of goodwill impairment. The qualitative assessment considers several factors including the excess fair value over carrying value as of the last quantitative impairment test, the length of time since the last fair value measurement, the current carrying value, market conditions, actual performance compared to forecasted performance, and the current business outlook. If the qualitative assessment indicates that it is more likely than not that goodwill is impaired, the reporting unit is then quantitatively tested for impairment. If a quantitative assessment is required, the fair value is determined using a variety of assumptions including estimated future cash flows of the reporting unit and applicable discount rates. Definite Lived Intangible Assets The cost of intangible assets with determinable useful lives is amortized to reflect the pattern of economic benefits consumed, either on a straight-line or accelerated basis over the estimated periods benefited. Customer relationships, trade names and other non-contractual intangible assets with determinable lives are amortized over periods generally ranging from 3 to 20 years. Intangible assets are tested for impairment if events or circumstances occur indicating that the respective asset might be impaired. Income Taxes Our income tax provision is recorded in accordance with a full-year forecasted rate methodology, including discrete items in the periods in which they occur. We recognize deferred tax assets and liabilities to reflect the future tax consequences of events that have been recognized in the financial statements or tax returns.  A deferred tax asset or liability results from the temporary difference between an item’s carrying value as reflected in the financial statements and its tax basis, and is calculated using enacted applicable tax rates.  We assess the likelihood that our deferred tax assets will be recovered from future taxable income and, to the extent we believe that recovery is not likely, a valuation allowance is established.  Changes in the valuation allowance, when recorded, are included in the provision for income taxes in the condensed consolidated financial statements.  We classify interest expense and penalties as part of our provision for income taxes based upon applicable federal and state interest/underpayment percentages. We assess uncertainty regarding tax positions taken in previously filed returns and record reserves in accordance with the guidance under the Financial Accounting Standards Board ("FASB") Accounting Standards Codification ("ASC") 740-10, "Accounting for Uncertainty in Income Taxes". Other Postretirement Benefits We account for postretirement benefits other than pensions by accruing the costs of benefits to be provided over the eligible employees’ periods of active service.  These costs are determined on an actuarial basis.  Our condensed consolidated balance sheets reflect the funded status of postretirement benefits. Pension Plan We sponsor a noncontributory defined benefit pension plan accounted for by accruing the cost to provide the benefits over the eligible employees’ periods of active service.  These costs are determined on an actuarial basis.  Our condensed consolidated balance sheets reflect the funded status of the defined benefit pension plan. Leases We determine if an arrangement is a lease at inception. Operating leases are included in operating lease right-of-use (“ROU”) assets, current operating lease liabilities, and non-current operating lease liabilities on our condensed consolidated balance sheets. Amounts related to finance leases are included in property and equipment, current portion of long-term debt, and long-term debt on our condensed consolidated balance sheets. ROU assets and lease liabilities are recognized and measured on the date the underlying asset is made available to us. Operating lease ROU assets and operating lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term at commencement date. We use our incremental borrowing rate based on the information available at the commencement date in determining the present value of future payments. The operating lease ROU asset also includes any lease payments made and excludes lease incentives. Our lease terms may include options to extend or terminate the lease when it is reasonably certain that we will exercise that option. Operating lease expense for minimum lease payments is recognized on a straight-line basis over the lease term. For certain leases, such as real estate and information technology (IT) equipment, we account for the lease and non-lease components as a single lease component. For all other leases, we account for the lease and non-lease components separately. We have elected as an accounting policy not to apply the recognition requirements for short-term leases. Therefore, leases with a term of twelve months or less are not recorded on the condensed consolidated balance sheets. Lease expenses associated with short-term leases are immaterial and are recorded in the condensed consolidated statements of income in selling, general and administrative expenses. Additionally, for certain vehicle leases, we apply a portfolio approach to account for the operating lease ROU assets and liabilities. Non-operating Expenses Non-operating expenses are comprised of interest expense, net and non-service cost components of the net periodic benefit cost for the pension and other postretirement benefit plans. The non-service cost components include interest cost, expected return on plan assets, amortization of net actuarial gains/losses, amortization of prior service costs/gains, and charges due to settlement of certain plan liabilities. New Accounting Standards In June 2016, the FASB issued Accounting Standard Update (“ASU” or “Update”) 2016-13, "Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments which introduced new guidance for the accounting for credit losses on certain financial instruments. The amendments in this ASU were effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years and required a cumulative-effect adjustment to the balance sheet as of the beginning of the first reporting period in which the guidance is effective. Periods presented prior to the adoption date are not adjusted. We adopted this Update as of January 1, 2020. We determined that our trade receivables are financial instruments subject to this Update. We evaluated the accounting policies applicable to our allowance for doubtful accounts and developed new methods to include three components into our allowance to comply with requirements of the ASU: 1) a reserve derived from historical loss rates based upon the aging of our trade receivables, 2) a reserve based upon specifically-identified trade receivables in our portfolio that are considered higher risk based on current conditions, and 3) an additional reserve, as necessary, to consider the impact of future economic conditions. The adoption of this Update did not have a material impact on our consolidated financial statements. In August 2018, the FASB issued ASU 2018-13, "Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement" ("ASU 2018-13") that makes minor changes to the disclosure requirements on fair value measurements in Topic 820. The guidance eliminates requirements for certain disclosures that are no longer considered cost beneficial and adds new disclosure requirements that the FASB considers pertinent. We adopted this Update as of January 1, 2020. The adoption did not have a material impact on our consolidated financial statements. In August 2018, the FASB issued ASU 2018-15, "Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract" ("ASU 2018-15") requiring a customer in a cloud computing arrangement that is a service contract to follow the internal use software guidance in ASC 350-40 to determine which implementation costs to capitalize as assets. Capitalized implementation costs related to a hosting arrangement that is a service contract will be amortized over the term of the hosting arrangement, beginning when the module or component of the hosting arrangement is ready for its intended use. We adopted this Update as of January 1, 2020. The adoption did not have a material impact on our consolidated financial statements. In August 2018, the FASB issued ASU 2018-14, "Compensation-Retirement Benefits-Defined Benefit Plans-General (Subtopic 715-20): Disclosure Framework-Changes to the Disclosure Requirements for Defined Benefit Plans" ("ASU 2018-14") that makes minor changes to the disclosure requirements for employers that sponsor defined benefit pension and/or other postretirement benefit plans. The guidance eliminates requirements for certain disclosures that are no longer considered cost beneficial and adds new disclosure requirements that the FASB considers pertinent. ASU 2018-14 is effective for fiscal years ending after December 15, 2020 for public entities. Early adoption is permitted. We are currently evaluating the impact of the adoption of the Update on our consolidated financial statements, but do not expect it to have a material impact. We plan to adopt the Update beginning on January 1, 2021. In March 2020, the FASB issued ASU 2020-04, “Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting” (“ASU 2020-04”) that provides temporary relief to the GAAP guidance on contract modifications and hedge accounting to ease the financial reporting burdens of the expected market transition from LIBOR and other interbank offered rates to alternative rates. This Update is effective for all entities as of March 12, 2020 through December 31, 2022. The guidance on contract modifications, which is applicable to Graybar, can be applied prospectively from any date beginning March 12, 2020 and may also be applied to modifications of existing contracts made earlier in the interim period that includes March 12, 2020. We are currently evaluating the impact of the adoption of the Update on our contracts and our consolidated financial statements.