| Cover | Sep. 24, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Sep. 24, 2021 |
| Entity Registrant Name | STAR GROUP, L.P. |
| Entity Central Index Key | 0001002590 |
| Entity Emerging Growth Company | false |
| Entity File Number | 001-14129 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 06-1437793 |
| 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 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Units |
| Trading Symbol | SGU |
| Security Exchange Name | NYSE |
