Summary of Significant Accounting Policies (Policies)	3 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2017
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation. The consolidated financial statements include the accounts of AmeriGas Partners, its majority-owned subsidiary AmeriGas OLP, and its 100%-owned finance subsidiaries AmeriGas Finance Corp., AmeriGas Eagle Finance Corp., AP Eagle Finance Corp., and AmeriGas Finance LLC. AmeriGas Partners and AmeriGas OLP are under the common control of the General Partner. The General Partner of AmeriGas OLP, which is also the General Partner of AmeriGas Partners, makes all decisions for AmeriGas OLP; limited partners of AmeriGas OLP do not have the ability to remove the General Partner or participate in the decision-making for AmeriGas OLP. The accounts of AmeriGas OLP are included based upon the determination that AmeriGas Partners has a controlling financial interest in and is the primary beneficiary of AmeriGas OLP.
Allocation of Net Income (Loss)	Allocation of Net Income (Loss). Net income (loss) attributable to AmeriGas Partners, L.P. is allocated to the General Partner and the limited partners in accordance with their respective ownership percentages after giving effect to amounts distributed to the General Partner in excess of its 1% general partner interest in AmeriGas Partners based on its incentive distribution rights (“IDRs”) under the Fourth Amended and Restated Agreement of Limited Partnership of AmeriGas Partners, L.P., as amended (“Partnership Agreement”).
Net Income (Loss) Per Unit	Net Income (Loss) Per Unit. Income (loss) per limited partner unit is computed in accordance with GAAP regarding the application of the two-class method for determining income (loss) per unit for master limited partnerships (“MLPs”) when IDRs are present. The two-class method requires that income per limited partner unit be calculated as if all earnings for the period were distributed and requires a separate calculation for each quarter- and year-to-date period. In periods when our net income attributable to AmeriGas Partners exceeds our Available Cash, as defined in the Partnership Agreement, and is above certain levels, the calculation according to the two-class method results in an increased allocation of undistributed earnings to the General Partner. Generally, in periods when our Available Cash in respect of the quarter- or year-to-date periods exceeds our net income (loss) attributable to AmeriGas Partners, the calculation according to the two-class method results in an allocation of earnings to the General Partner greater than its relative ownership interest in the Partnership (or in the case of a net loss attributable to AmeriGas Partners, an allocation of such net loss to the Common Unitholders greater than their relative ownership interest in the Partnership).
Derivative Instruments	Derivative Instruments. Derivative instruments are reported in the condensed consolidated balance sheets at their fair values, unless the derivative instruments qualify for the normal purchase and normal sale (“NPNS”) exception under GAAP. The accounting for changes in fair value depends upon the purpose of the derivative instrument and whether it is designated and qualifies for hedge accounting. Changes in the fair values of these derivative instruments are reflected in “Cost of sales — propane” on the Condensed Consolidated Statements of Operations. Cash flows from derivative instruments are included in cash flows from operating activities.
Use of Estimates	Use of 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, expenses and costs. These estimates are based on management’s knowledge of current events, historical experience and various other assumptions that are believed to be reasonable under the circumstances. Accordingly, actual results may be different from these estimates and assumptions.
Reclassifications	Reclassifications. Certain prior-period amounts have been reclassified to conform to the current-period presentation.
Accounting Standards Not Yet Updated	Accounting Standards Not Yet Adopted Derivatives and Hedging. In August 2017, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2017-12, “Targeted Improvements to Accounting for Hedging Activities.” This ASU amends and simplifies existing guidance to allow companies to more accurately present the economic effects of risk management activities in the financial statements. The amendments in this ASU are effective for interim and annual periods beginning after December 15, 2018 (Fiscal 2020). Early adoption is permitted. For cash flow and net investment hedges as of the adoption date, the guidance requires a modified retrospective approach. The amended presentation and disclosure guidance is required only prospectively. The Partnership is in the process of assessing the impact on its financial statements from the adoption of the new guidance and determining the period in which the new guidance will be adopted. Leases. In February 2016, the FASB issued ASU No. 2016-02, "Leases." This ASU amends existing guidance to require entities that lease assets to recognize the assets and liabilities for the rights and obligations created by those leases on the balance sheet. The new guidance also requires additional disclosures about the amount, timing and uncertainty of cash flows from leases. The amendments in this ASU are effective for annual reporting periods beginning after December 15, 2018 (Fiscal 2020). Early adoption is permitted. Lessees must apply a modified retrospective transition approach for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. The Partnership is in the process of assessing the impact on its financial statements from the adoption of the new guidance but anticipates an increase in the recognition of right-of-use assets and lease liabilities. Revenue Recognition. In May 2014, the FASB issued ASU No. 2014-09, “Revenue from Contracts with Customers” (“ASU 2014-09”). The guidance provided under ASU 2014-09, as amended, supersedes the revenue recognition requirements in ASC No. 605, “Revenue Recognition,” and most industry-specific guidance included in the ASC. ASU 2014-09 requires that an entity recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The new guidance is effective for the Partnership for interim and annual periods beginning after December 15, 2017 (Fiscal 2019) and allows for either full retrospective adoption or modified retrospective adoption. The Partnership is in the process of analyzing the impact of the new guidance using an integrated approach which includes evaluating differences in the amount and timing of revenue recognition from applying the requirements of the new guidance, reviewing its accounting policies and practices, and assessing the need for changes to its processes, accounting systems and design of internal controls. The Partnership has completed the assessment of a significant number of its contracts with customers under the new guidance to determine the effect of the adoption of the new guidance. Although the Partnership has not completed its assessment of the impact of the new guidance, the Partnership does not expect its adoption will have a material impact on its consolidated financial statements. The Partnership currently anticipates that it will adopt the new standard using the modified retrospective transition method effective October 1, 2018. The ultimate decision with respect to the transition method that it will use will depend upon the completion of the Partnership’s analysis including confirming its preliminary conclusion that the adoption of the new guidance will not have a material impact on its consolidated financial statements.