<?xml version="1.0" encoding="utf-8"?>
<xbrl
  xmlns="http://www.xbrl.org/2003/instance"
  xmlns:dei="http://xbrl.sec.gov/dei/2024"
  xmlns:iso4217="http://www.xbrl.org/2003/iso4217"
  xmlns:link="http://www.xbrl.org/2003/linkbase"
  xmlns:xlink="http://www.w3.org/1999/xlink">
    <link:schemaRef xlink:href="sgu-20240930.xsd" xlink:type="simple"/>
    <context id="C_105e7c1f-e4ea-42ac-9e59-49b80cd1d6ae">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001002590</identifier>
        </entity>
        <period>
            <instant>2024-11-30</instant>
        </period>
    </context>
    <context id="C_5b780d4d-50df-44ee-b99a-a22cb6a16f24">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001002590</identifier>
        </entity>
        <period>
            <instant>2024-03-31</instant>
        </period>
    </context>
    <context id="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa">
        <entity>
            <identifier scheme="http://www.sec.gov/CIK">0001002590</identifier>
        </entity>
        <period>
            <startDate>2023-10-01</startDate>
            <endDate>2024-09-30</endDate>
        </period>
    </context>
    <unit id="U_shares">
        <measure>shares</measure>
    </unit>
    <unit id="U_USD">
        <measure>iso4217:USD</measure>
    </unit>
    <dei:DocumentFiscalPeriodFocus
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_a997818a-bf6c-4f0b-8a1e-82851c0b4d54">FY</dei:DocumentFiscalPeriodFocus>
    <dei:EntityCentralIndexKey
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_7d124a6d-99d5-4769-85f2-6ddae9f8530e">0001002590</dei:EntityCentralIndexKey>
    <dei:CurrentFiscalYearEndDate
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_7332c88e-3a2c-44f6-bb9d-2992525dbdd1">--09-30</dei:CurrentFiscalYearEndDate>
    <dei:AmendmentFlag
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_d055727e-396d-44bb-8f3e-78b4b6fe6d8c">true</dei:AmendmentFlag>
    <dei:DocumentType
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_f07acc99-b64f-425d-8562-e4a8dee64f47">10-K/A</dei:DocumentType>
    <dei:DocumentAnnualReport
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_60106dc1-c084-4e76-8fb3-e357e781a035">true</dei:DocumentAnnualReport>
    <dei:DocumentPeriodEndDate
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_dd8fc9e5-ed3f-450d-99e5-7f9f111ac5dc">2024-09-30</dei:DocumentPeriodEndDate>
    <dei:DocumentFiscalYearFocus
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_e29906f4-d768-4075-8fee-056f17904978">2024</dei:DocumentFiscalYearFocus>
    <dei:DocumentTransitionReport
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_cc43462a-c66d-4e8c-878a-def02c8cc4b4">false</dei:DocumentTransitionReport>
    <dei:EntityFileNumber
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_6374b282-c6b7-4fd3-b327-ba0e6dbc8d1c">001-14129</dei:EntityFileNumber>
    <dei:EntityRegistrantName
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_d8fdd2dc-eef3-42ff-b3e0-bd56dcccd5ae">STAR GROUP, L.P.</dei:EntityRegistrantName>
    <dei:EntityIncorporationStateCountryCode
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_9cd4e1d4-fc3f-4690-a504-d0f0f2547b17">DE</dei:EntityIncorporationStateCountryCode>
    <dei:EntityTaxIdentificationNumber
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_89d7da51-51b7-416b-ae24-3f7b61094286">06-1437793</dei:EntityTaxIdentificationNumber>
    <dei:EntityAddressAddressLine1
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_39be3a5f-530a-4ac2-91e7-29e0662a8c06">9 West Broad Street</dei:EntityAddressAddressLine1>
    <dei:EntityAddressAddressLine2
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_f83e8768-03a4-4f93-8834-f7d5bf07f888">Suite 310</dei:EntityAddressAddressLine2>
    <dei:EntityAddressCityOrTown
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_c0733dba-324f-4cb5-a7d6-fe42c5795422">Stamford</dei:EntityAddressCityOrTown>
    <dei:EntityAddressStateOrProvince
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_22028768-3530-4c8f-a224-f9d9983eb9a4">CT</dei:EntityAddressStateOrProvince>
    <dei:EntityAddressPostalZipCode
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_e9cfeece-23dc-4bb0-9402-bebb3f52f39c">06902</dei:EntityAddressPostalZipCode>
    <dei:CityAreaCode
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_4760c346-37e9-4129-b6ed-c0fc260a533e">(203)</dei:CityAreaCode>
    <dei:LocalPhoneNumber
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_4e8c5627-d38c-4759-a195-1aabdadbc748">328-7310</dei:LocalPhoneNumber>
    <dei:Security12bTitle
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_62b2a695-0822-45b7-aba9-833312e54aee">Common Units</dei:Security12bTitle>
    <dei:TradingSymbol
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_4353c0dd-83bc-48dc-955e-f816fab457ff">SGU</dei:TradingSymbol>
    <dei:SecurityExchangeName
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_f032ee83-6d5c-46c1-af60-18580082b238">NYSE</dei:SecurityExchangeName>
    <dei:EntityWellKnownSeasonedIssuer
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_73f6cf2d-a79e-4ff3-a38c-7e5b0610ddf6">No</dei:EntityWellKnownSeasonedIssuer>
    <dei:EntityVoluntaryFilers
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_a445a410-b22a-41ff-b0bc-48b9e3ab04c6">No</dei:EntityVoluntaryFilers>
    <dei:EntityCurrentReportingStatus
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_d179003e-e415-48be-813c-71f30e205fe7">Yes</dei:EntityCurrentReportingStatus>
    <dei:EntityInteractiveDataCurrent
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_f05e7c65-7b35-47aa-85b1-90c47d557bfe">Yes</dei:EntityInteractiveDataCurrent>
    <dei:EntityFilerCategory
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_d224fa29-613f-48c6-9ce0-4708acfcbff5">Accelerated Filer</dei:EntityFilerCategory>
    <dei:EntitySmallBusiness
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_907987d8-2080-4f26-aff9-c3e252c6f179">false</dei:EntitySmallBusiness>
    <dei:EntityEmergingGrowthCompany
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_34525056-945e-4698-815c-7daa9b8f92fa">false</dei:EntityEmergingGrowthCompany>
    <dei:IcfrAuditorAttestationFlag
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_89d051fe-3d83-46bd-bc14-eca2ecc25b2c">true</dei:IcfrAuditorAttestationFlag>
    <dei:DocumentFinStmtErrorCorrectionFlag
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_0d8c0d0c-4e86-4b2d-978c-bd709861fd7b">false</dei:DocumentFinStmtErrorCorrectionFlag>
    <dei:EntityShellCompany
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_ddf56ebf-c64d-4725-b0f9-dc2d66a5247d">false</dei:EntityShellCompany>
    <dei:EntityPublicFloat
      contextRef="C_5b780d4d-50df-44ee-b99a-a22cb6a16f24"
      decimals="0"
      id="F_d219bbd6-3366-4953-98c2-ae61f1f4eaaf"
      unitRef="U_USD">313349949</dei:EntityPublicFloat>
    <dei:EntityCommonStockSharesOutstanding
      contextRef="C_105e7c1f-e4ea-42ac-9e59-49b80cd1d6ae"
      decimals="INF"
      id="F_f29a7225-11c1-4bad-8573-313c28f09d7b"
      unitRef="U_shares">34577855</dei:EntityCommonStockSharesOutstanding>
    <dei:AmendmentDescription
      contextRef="C_5fff0d49-98fd-4a3d-aabc-2aa510883afa"
      id="F_08e378e4-a3eb-4183-8f19-0cd3eaeed550">This Amendment No. 2 on Form 10-K/A (this &#x201c;Amendment&#x201d;) amends our Annual Report on Form 10-K for the fiscal year ended September 30, 2024 of Star Group, L.P. as filed with the Securities and Exchange Commission (the &#x201c;SEC&#x201d;) on December 4, 2024, as amended by Amendment No. 1 to Form 10-K as filed with the SEC on February 25, 2025 (the &#x201c;Original Filing&#x201d;).  This Amendment is being filed solely to incorporate by reference previously-filed  Exhibit 3.4 and Exhibit 4.1 that were inadvertently omitted from the Index to Exhibits in the Original Filing. No other changes have been made to the Original Form 10-K.This Amendment does not amend or update any other information set forth in the Original Filing and we have not updated disclosures contained therein to reflect any events that occurred at a date subsequent to date of the Original Filing.Pursuant to Rule 12b-15 of the Securities Exchange Act of 1934, as amended (the &#x201c;Exchange Act&#x201d;), currently dated certifications are filed herewith as exhibits to this Amendment pursuant to Rule 13a-14(a) or 15d-14(a) of the Exchange Act under Item 15 of Part IV hereof. Because no financial statements have been included in this Amendment and this Amendment does not contain any disclosure with respect to Items 307 and 308 of Regulation S-K, paragraphs 3, 4, and 5 of the certifications have been omitted. Similarly, because no financial statements have been included in this Amendment, certifications pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 have been omitted.</dei:AmendmentDescription>
</xbrl>
