Document and Entity Information - USD ($)	12 Months Ended
	Sep. 30, 2024	Nov. 30, 2024	Mar. 31, 2024
Cover [Abstract]
Document Type	10-K/A
Amendment Flag	true
Document Period End Date	Sep. 30, 2024
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	FY
Trading Symbol	SGU
Title of 12(b) Security	Common Units
Security Exchange Name	NYSE
Entity Registrant Name	STAR GROUP, L.P.
Entity Central Index Key	0001002590
Entity Tax Identification Number	06-1437793
Current Fiscal Year End Date	--09-30
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Interactive Data Current	Yes
Entity Incorporation, State or Country Code	DE
Document Annual Report	true
Document Transition Report	false
Entity File Number	001-14129
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		34,577,855
Entity Public Float			$ 313,349,949
Entity Address, Address Line One	9 West Broad Street
Entity Address, Address Line Two	Suite 310
Entity Address, City or Town	Stamford
Entity Address, State or Province	CT
Entity Address, Postal Zip Code	06902
City Area Code	(203)
Local Phone Number	328-7310
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Amendment Description	This Amendment No. 1 on Form 10-K/A (this “Amendment”) amends Item 10. (Directors, Executive Officers and Corporate Governance) in 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 on December 4, 2024 (the “Original Filing”). The purpose of this Amendment is to (i) furnish the information required by Item 408(b) of Regulation S-K and (ii) supplement the Exhibits contained in Item 15(a)(3) of Part IV of the Original Filing to include Exhibit 19, Insider Trading Policy. These items were inadvertently omitted in the Original Filing.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 “Exchange Act”), 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.