| Cover Document | Aug. 10, 2023 |
| Cover [Abstract] | |
| Pre-commencement Issuer Tender Offer | false |
| Pre-commencement Tender Offer | false |
| Soliciting Material | false |
| Written Communications | false |
| Title of 12(b) Security | Common Stock, $0.01 par value |
| Document Type | 8-K |
| Document Period End Date | Aug. 10, 2023 |
| Entity Registrant Name | StoneX Group Inc. |
| Entity Address, Address Line One | 230 Park Ave |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 000-23554 |
| Entity Tax Identification Number | 59-2921318 |
| Entity Address, Address Line Two | 10th Floor |
| Entity Address, City or Town | New York |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 10169 |
| City Area Code | (212) |
| Local Phone Number | 485-3500 |
| Trading Symbol | SNEX |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000913760 |
| Amendment Flag | false |
| Current Fiscal Year End Date | --09-30 |
