Summary of Significant Accounting Policies	6 Months Ended
Jun. 30, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	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 United States 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 and Management’s Discussion and Analysis of Financial Condition and Results of Operations as of and for the year ended December 31, 2016, 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 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. Subsequent Events We have evaluated subsequent events through the time of the filing of this Quarterly Report on Form 10-Q with the Commission. No material subsequent events have occurred since June 30, 2017 that require recognition or disclosure in these financial statements. 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 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 We record certain 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 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 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 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 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 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 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/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 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 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 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. 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 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 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. New Accounting Standards No new accounting standards that were issued or became effective during 2017 have had or are expected to have a material impact on our condensed consolidated financial statements except those noted below: In March 2017, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update (“ASU” or “Update”) 2017-07, “Compensation - Retirement Benefits (Topic 715)” ("ASU 2017-07"). The changes to the standard require employers to report the service cost component in the same line as other compensation costs arising from services rendered by employees during the reporting period. The other components of net benefit costs will be presented in the income statement separately from the service cost and outside of a subtotal of income from operations. In addition, only the service cost component may be eligible for capitalization where applicable. ASU 2017-07 is effective for interim and annual reporting periods beginning after December 15, 2017. We are currently evaluating the impact ASU 2017-07 will have on our condensed consolidated financial statements. In February 2016, the FASB issued ASU 2016-02, “Leases (Topic 842)” ("ASU 2016-02"). 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 condensed consolidated financial statements. In May 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers”, with amendments in 2015 and 2016 ("ASU 2014-09"). The guidance was initially effective January 1, 2017 and early adoption was not permitted. The amended guidance provides for a one-year deferral of the effective date to January 1, 2018, with an option of applying the standard on the original effective date. The new standard and related amendments provide for two alternative implementation methods: a full retrospective approach and a modified retrospective approach. The full retrospective approach applies the new standard retrospectively to each prior reporting period presented. This method allows the use of certain practical expedients. The modified retrospective approach applies the new standard retrospectively in the year of initial adoption and records 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 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. Our primary source of revenues is from customer purchase orders in the construction, industrial & utility, and CIG markets for electrical and comm/data products. Revenue is currently 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. Given the scope of work required to implement the recognition and disclosure requirements under the new standard, we have identified and are currently assessing our revenue streams and reporting disclosures to determine the potential impact related to the adoption of ASU 2014-09. We do however believe that, upon adoption of ASU 2014-09, the timing of revenue related to our sales will remain relatively consistent with current practices. At the time of this filing, we still believe we will be adopting ASU 2014-09 under the modified retrospective approach although we continue to assess all potential impacts of the guidance and given normal ongoing business dynamics, preliminary conclusions are subject to change.

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 United States 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 and Management’s Discussion and Analysis of Financial Condition and Results of Operations as of and for the year ended December 31, 2016, 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 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.

Subsequent Events

We have evaluated subsequent events through the time of the filing of this Quarterly Report on Form 10-Q with the Commission. No material subsequent events have occurred since June 30, 2017 that require recognition or disclosure in these financial statements.

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 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

We record certain 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 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

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

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 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 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

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/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

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

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 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.

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 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 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.

New Accounting Standards

No new accounting standards that were issued or became effective during 2017 have had or are expected to have a material impact on our condensed consolidated financial statements except those noted below:

In March 2017, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update (“ASU” or “Update”) 2017-07, “Compensation - Retirement Benefits (Topic 715)” ("ASU 2017-07"). The changes to the standard require employers to report the service cost component in the same line as other compensation costs arising from services rendered by employees during the reporting period. The other components of net benefit costs will be presented in the income statement separately from the service cost and outside of a subtotal of income from operations. In addition, only the service cost component may be eligible for capitalization where applicable. ASU 2017-07 is effective for interim and annual reporting periods beginning after December 15, 2017. We are currently evaluating the impact ASU 2017-07 will have on our condensed consolidated financial statements.

In February 2016, the FASB issued ASU 2016-02, “Leases (Topic 842)” ("ASU 2016-02"). 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 condensed consolidated financial statements.

In May 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers”, with amendments in 2015 and 2016 ("ASU 2014-09"). The guidance was initially effective January 1, 2017 and early adoption was not permitted. The amended guidance provides for a one-year deferral of the effective date to January 1, 2018, with an option of applying the standard on the original effective date.

The new standard and related amendments provide for two alternative implementation methods: a full retrospective approach and a modified retrospective approach. The full retrospective approach applies the new standard retrospectively to each prior reporting period presented. This method allows the use of certain practical expedients. The modified retrospective approach applies the new standard retrospectively in the year of initial adoption and records 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 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.

Our primary source of revenues is from customer purchase orders in the construction, industrial & utility, and CIG markets for electrical and comm/data products. Revenue is currently 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. Given the scope of work required to implement the recognition and disclosure requirements under the new standard, we have identified and are currently assessing our revenue streams and reporting disclosures to determine the potential impact related to the adoption of ASU 2014-09. We do however believe that, upon adoption of ASU 2014-09, the timing of revenue related to our sales will remain relatively consistent with current practices. At the time of this filing, we still believe we will be adopting ASU 2014-09 under the modified retrospective approach although we continue to assess all potential impacts of the guidance and given normal ongoing business dynamics, preliminary conclusions are subject to change.