Basis of Presentation (Policies)	6 Months Ended
Basis of Presentation (Policies)	Jun. 30, 2017
Accounting Policies [Abstract]
Basis of Accounting	The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with the instructions to Form 10-Q and therefore do not include all information and footnotes required by accounting principles generally accepted in the United States for complete financial statements. Except as disclosed herein, there has been no material change in the information disclosed in the notes to the consolidated financial statements included in the Annual Report on Form 10-K of Genuine Parts Company (the “Company”) for the year ended December 31, 2016. Accordingly, the unaudited interim condensed consolidated financial statements and related disclosures herein should be read in conjunction with the Company’s 2016 Annual Report on Form 10-K.
Use of Estimates	The preparation of interim financial statements requires management to make estimates and assumptions for the amounts reported in the condensed consolidated financial statements. Specifically, the Company makes estimates and assumptions in its interim condensed consolidated financial statements for inventory adjustments, the accrual of bad debts, customer sales returns, and volume incentives earned, among others. Inventory adjustments (including adjustments for a majority of inventories that are valued under the last-in, first-out (“LIFO”) method) are accrued on an interim basis and adjusted in the fourth quarter based on the annual book to physical inventory adjustment and LIFO valuation, which is performed each year-end. Reserves for bad debts and customer sales returns are estimated and accrued on an interim basis based upon historical experience. Volume incentives are estimated based upon cumulative and projected purchasing levels. The estimates and assumptions for interim reporting may change upon final determination at year-end, and such changes may be significant.
Segment Reporting	Net sales by segment exclude the effect of certain discounts, incentives and freight billed to customers. The line item “Other” represents the net effect of the discounts, incentives and freight billed to customers, which is reported as a component of net sales in the Company’s condensed consolidated statements of income and comprehensive income.
Recent Accounting Pronouncements	In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers (Topic 606) ("ASU 2014-09"), which will create a single, comprehensive revenue recognition model for recognizing revenue from contracts with customers. The standard is effective for interim and annual reporting periods beginning after December 15, 2017 and may be adopted either retrospectively or on a modified retrospective basis. The core principle of the new standard is that a company should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. ASU 2014-09 defines a five-step process to achieve this core principle and, in doing so, it is possible more judgment and estimates may be required within the revenue recognition process than are required under existing guidance, including identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation, among others. The Company has established a cross-functional implementation team to evaluate and implement the new standard related to the recognition of revenue from contracts with customers. The Company primarily sells goods and recognizes revenue at point of sale or delivery and this will not change under the new standard. We are completing an analysis of revenue streams at each of the business units and are evaluating the impact the new standard may have on revenue recognition. In addition, the Company is evaluating recently issued guidance on practical expedients as part of the transition decision. The Company plans to use the modified retrospective adoption method and does not believe there will be a material impact to the Company’s consolidated revenues upon adoption. The Company will continue to evaluate the impacts of the pending adoption of ASU 2014-09 and the preliminary assessments are subject to change. In July 2015, the FASB issued ASU 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory ("ASU 2015-11"), which modifies existing requirements regarding measuring first-in, first-out and average cost inventory at the lower of cost or market. Under existing standards, the market amount requires consideration of replacement cost, net realizable value (“NRV”), and NRV less an approximately normal profit margin. ASU 2015-11 replaces market with NRV, defined as estimated selling prices in the ordinary course of business, less reasonably predictable costs of completion, disposal and transportation. This eliminates the need to determine and consider replacement cost or NRV less an approximately normal profit margin when measuring inventory. The Company adopted ASU 2015-11 on January 1, 2017 and it did not have a material impact to the Company's condensed consolidated financial statements for the six months ended June 30, 2017 and it will not have a material impact on the annual consolidated financial statements. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) ("ASU 2016-02"), which requires an entity to recognize a right-of-use asset and a lease liability on the balance sheet for all leases, including operating leases, with a term greater than twelve months. Expanded disclosures with additional qualitative and quantitative information will also be required. This guidance is effective for interim and annual reporting periods beginning after December 15, 2018 and early adoption is permitted. The new standard must be adopted using a modified retrospective transition. The Company is currently evaluating the impact of ASU 2016-02 on its condensed consolidated financial statements and related disclosures. As disclosed in the leased properties footnote in the 2016 Annual Report on Form 10-K, the future minimum payments under noncancelable operating leases are approximately $865.0 million and the Company does believe the adoption of this standard will have a significant impact on the consolidated balance sheets. In March 2016, the FASB issued ASU 2016-09, Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting ("ASU 2016-09") that changes the accounting for certain aspects of share-based compensation to employees including forfeitures, employer tax withholding, and the financial statement presentation of excess tax benefits or expense. ASU 2016-09 also clarifies the statement of cash flows presentation for certain components of share-based compensation, which prospectively reclassifies cash flows from excess tax benefits of share-based compensation currently disclosed in financing activities to operating activities in the period of adoption. The guidance will increase income tax expense volatility, as well as the Company's cash flows from operations. In addition, the Company did not elect to change shares withheld for employment income tax purposes, or the current methodology of estimating forfeitures upon adoption. The Company adopted ASU 2016-09 on January 1, 2017 on a prospective basis. The adoption of ASU 2016-09 did not have a material impact to the Company's condensed consolidated financial statements for the six months ended June 30, 2017 and it is not expected to have a material impact on the annual consolidated financial statements or related disclosures. In March 2017, the FASB issued ASU 2017-07, Compensation-Retirement Benefits (Topic 715) ("ASU 2017-07"), which requires an entity to report the service cost component of net periodic benefit cost in the same line item as other compensation costs (selling, administrative and other expenses), and the remaining components in non-operating expense in the consolidated statement of income and comprehensive income. This standard is effective for interim and annual reporting periods beginning after December 15, 2017 and early adoption is permitted. The Company will adopt ASU 2017-07 on January 1, 2018 and it is not expected to have a material impact on the Company’s consolidated financial statements or related disclosures.
Share-based Compensation	As more fully discussed in Note 5 of the Company’s notes to the consolidated financial statements in its 2016 Annual Report on Form 10-K, the Company maintains various long-term incentive plans, which provide for the granting of stock options, stock appreciation rights (“SARs”), restricted stock, restricted stock units (“RSUs”), performance awards, dividend equivalents and other share-based awards. SARs represent a right to receive upon exercise an amount, payable in shares of common stock, equal to the excess, if any, of the fair market value of the Company’s common stock on the date of exercise over the base value of the grant. The terms of such SARs require net settlement in shares of common stock and do not provide for cash settlement. RSUs represent a contingent right to receive one share of the Company’s common stock at a future date. The majority of awards previously granted vest on a pro-rata basis for periods ranging from one to five years and are expensed accordingly on a straight-line basis. The Company issues new shares upon exercise or conversion of awards under these plans. Most awards may be exercised or converted to shares not earlier than twelve months nor later than ten years from the date of grant.
Guarantees	The Company guarantees the borrowings of certain independently controlled automotive parts stores (“independents”) and certain other affiliates in which the Company has a noncontrolling equity ownership interest (“affiliates”). Presently, the independents are generally consolidated by unaffiliated enterprises that have controlling financial interests through ownership of a majority voting interest in the independents. The Company has no voting interest or equity conversion rights in any of the independents. The Company does not control the independents or the affiliates, but receives a fee for the guarantees. The Company has concluded that the independents are variable interest entities, but that the Company is not the primary beneficiary. Specifically, the equity holders of the independents have the power to direct the activities that most significantly impact the entities’ economic performance including, but not limited to, decisions about hiring and terminating personnel, local marketing and promotional initiatives, pricing and selling activities, credit decisions, monitoring and maintaining appropriate inventories, and store hours. Separately, the Company concluded the affiliates are not variable interest entities. The Company’s maximum exposure to loss as a result of its involvement with these independents and affiliates is generally equal to the total borrowings subject to the Company’s guarantees. While such borrowings of the independents and affiliates are outstanding, the Company is required to maintain compliance with certain covenants, including a maximum debt to capitalization ratio and certain limitations on additional borrowings. At June 30, 2017, the Company was in compliance with all such covenants. In the event that the Company is required to make payments in connection with guaranteed obligations of the independents or the affiliates, the Company would obtain and liquidate certain collateral (e.g., accounts receivable and inventory) to recover all or a portion of the amounts paid under the guarantees. When it is deemed probable that the Company will incur a loss in connection with a guarantee, a liability is recorded equal to this estimated loss.
Fair Value of Financial Instruments	The carrying amounts reflected in the condensed consolidated balance sheets for cash and cash equivalents, trade accounts receivable, trade accounts payable, and borrowings under the line of credit approximate their respective fair values based on the short-term nature of these instruments. The fair value of fixed rate debt is designated as Level 2 in the fair value hierarchy (i.e., significant observable inputs) and is based primarily on the discounted value of future cash flows using current market interest rates offered for debt of similar credit risk and maturity.