Accounting Policies (Policies)	12 Months Ended
Accounting Policies (Policies)	Dec. 31, 2015
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The 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	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.
Reclassifications	Reclassifications Certain reclassifications have been made to prior years' financial information to conform to the December 31, 2015 presentation.
Subsequent Events	Subsequent Events We have evaluated subsequent events through the time of the filing of this Annual Report on Form 10-K with the Commission. No material subsequent events have occurred since December 31, 2015 that require recognition or disclosure in our financial statements, other than the asset sale disclosed in Note 5, "Property and Depreciation".
Revenue Recognition	Revenue Recognition Revenue is recognized when evidence of a customer arrangement exists, prices are fixed and determinable, product title, ownership and risk of loss transfers to the customer, and collectability is reasonably assured. Revenues recognized are primarily for product sales, but also include freight and handling charges. Our standard shipping terms are FOB shipping point, under which product title passes to the customer at the time of shipment. We also earn revenue for services provided to customers for supply chain management and logistics services. Service revenue, which accounts for less than 1% of net sales, is recognized when services are rendered and completed. Revenue is reported net of all taxes assessed by governmental authorities as a result of revenue-producing transactions, primarily sales tax.
Outgoing Freight Expenses	Outgoing Freight Expenses We record certain outgoing freight expenses as a component of selling, general and administrative expenses. These costs totaled $51,100, $49,622, and $48,497 for the years ended December 31, 2015, 2014, and 2013, respectively.
Cash and Cash Equivalents	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 Doubtful Accounts	Allowance for Doubtful Accounts 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 and specific risks identified in the receivables portfolio. 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	Merchandise Inventory Our inventory is stated at the lower of cost (determined using the last-in, first-out (“LIFO”) cost method) or market. 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	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 the point at which we will have completed our performance under the agreement and the deferred amounts will be earned. We perform analysis 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 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	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 may be protected 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	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	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	Goodwill Our goodwill is not amortized, but rather tested annually for impairment. Goodwill is reviewed annually in the fourth quarter and/or 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	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 5 to 20 years. Intangible assets are tested for impairment if events or circumstances occur indicating that the respective asset might be impaired.
Income Taxes	Income Taxes 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. Uncertainty exists regarding tax positions taken in previously filed tax returns still subject to examination and positions expected to be taken in future 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 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.
Other Postretirement Benefits	Other Postretirement Benefits We account for postretirement benefits other than pensions by accruing the costs of benefits to be provided over the employees’ periods of active service. These costs are determined on an actuarial basis. Our consolidated balance sheets reflect the funded status of postretirement benefits.
Pension Plan	Pension Plan We sponsor a noncontributory defined benefit pension plan accounted for by accruing the cost to provide the benefits over the employees’ periods of active service. These costs are determined on an actuarial basis. Our consolidated balance sheets reflect the funded status of the defined benefit pension plan.
New Accounting Standards	New Accounting Standards No new accounting standards that were issued or became effective during 2015 have had or are expected to have a material impact on our consolidated financial statements except those noted below. Subsequent to December 31, 2015 but prior to issuance of this report, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update (“ASU” or “Update”) 2016-02, “Leases (Topic 842)”. The core principle of Topic 842 requires that a lessee should recognize the assets and liabilities on the balance sheet and disclose key information about leasing arrangements. The amendments in ASU 2016-02 are effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. The guidance is required to be adopted at the earliest period presented using a modified retrospective approach. We are currently evaluating the impact the provisions will have on our consolidated financial statements and whether we will adopt the guidance early. In November 2015, FASB issued ASU 2015-17, "Balance Sheet Classification of Deferred Taxes". The amendments in this Update require that deferred tax liabilities and assets be classified as non-current in a classified statement of financial position. This update applies to all entities that present a classified statement of financial position. The current requirement that deferred tax liabilities and assets of a tax-paying component of an entity be offset and presented as a single amount is not affected. The ASU is effective for public business entities for annual reporting periods beginning after December 15, 2016, and interim periods within those annual periods. Earlier application is permitted for all entities as of the beginning of an interim or annual reporting period. We early adopted the ASU 2015-17, and disclose the quantitative information about the effects of the accounting change on prior periods in Note 7, "Income Taxes". In April 2015, FASB issued ASU 2015-05, "Intangibles-Goodwill and Other-Internal-use Software: Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement". This Update provides guidance about whether a cloud computing arrangement includes a software license. If a cloud computing arrangement includes a software license, then the customer should account for the software license element of the arrangement consistent with the acquisition of other software licenses. If a cloud computing arrangement does not include a software license, the customer should account for the arrangement as a service contract and expensed as services are received. The Update is effective for fiscal years beginning after December 15, 2015 and interim periods. We do not expect the adoption of this Update to have a material impact on our results of operations, financial position, or cash flows. In February 2015, FASB issued ASU 2015-02, "Consolidation". The amendments in this Update affect reporting entities that are required to evaluate whether they should consolidate certain legal entities. All legal entities are subject to reevaluation under the revised consolidation model. This ASU is effective for public business entities for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2015. We do not expect the adoption of this Update to have a material impact on our results of operations, financial position, or cash flows. In May 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers”, which provides guidance on a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes current revenue recognition guidance, including industry-specific guidance. In July 2015, the FASB deferred the effective date of the Update for one year. The Update will now be effective for public business entities for annual reporting periods, including interim reporting periods, beginning after December 15, 2017. The new standard provides two alternative implementation methods. The first is to apply the new standard retrospectively to each prior reporting period presented. This method allows the use of certain practical expedients. The second method is to apply the new standard retrospectively in the year of initial adoption and record a cumulative effect adjustment for the impact of adjusting contracts open at the date of adoption. Under this transition method, we would apply this guidance retrospectively only to contracts that are not completed contracts at the date of initial application, which for us will be January 1, 2018. We would then recognize the cumulative effect of initially applying the standard as an adjustment to the opening balance of retained earnings. This method also requires us to disclose comparative information for the year of adoption. We continue to determine which method we will use to implement the new standard and to assess the impact the new standard is expected to have on the consolidated financial statements or on other matters or aspects of our business.