v3.26.1
Credit Facilities - Schedule of Debt (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Sep. 30, 2025
Line of Credit Facility [Line Items]    
Lenders under loans $ 660.7 $ 782.0
Uncommitted Credit Facilities 172.7 153.9
Note Payable to Bank 0.0 6.3
Total outstanding borrowings 1,821.6 1,941.0
Committed and Subordinated Credit Facilities    
Line of Credit Facility [Line Items]    
Total Commitment 1,760.0  
Lenders under loans 488.0 621.8
Senior Secured Notes due 2031    
Line of Credit Facility [Line Items]    
Senior secured notes 544.9 544.1
Senior Secured Notes due 2032    
Line of Credit Facility [Line Items]    
Senior secured notes 616.0 614.9
Line of Credit | Senior StoneX Group Inc. Committed Credit Facility - Revolving Line of Credit    
Line of Credit Facility [Line Items]    
Total Commitment 850.0  
Lenders under loans 190.0 317.0
Line of Credit | StoneX Financial Inc. Subordinated Credit Facility    
Line of Credit Facility [Line Items]    
Total Commitment 155.0  
Lenders under loans 60.0 0.0
Line of Credit | StoneX Commodity Solutions LLC    
Line of Credit Facility [Line Items]    
Total Commitment 325.0  
Line of Credit | Revolving commitments | StoneX Financial Inc.    
Line of Credit Facility [Line Items]    
Total Commitment 325.0  
Lenders under loans 75.0 0.0
Line of Credit | Revolving commitments | StoneX Commodity Solutions LLC    
Line of Credit Facility [Line Items]    
Total Commitment 200.0  
Lenders under loans 126.0 104.0
Line of Credit | Revolving commitments | Right Company LLC    
Line of Credit Facility [Line Items]    
Total Commitment 15.0  
Lenders under loans 7.0 0.0
Line of Credit | Revolving commitments | StoneX Financial Ltd.    
Line of Credit Facility [Line Items]    
Total Commitment 200.0  
Lenders under loans 30.0 90.0
Line of Credit | Revolving commitments | StoneX Financial Pte. Ltd.    
Line of Credit Facility [Line Items]    
Total Commitment 15.0  
Lenders under loans 0.0 0.0
Line of Credit | Uncommitted amounts | StoneX Commodity Solutions LLC    
Line of Credit Facility [Line Items]    
Total Commitment 125.0  
Subordinated Debt | R.J. O'Brien & Associates, LLC Subordinated Credit Facility    
Line of Credit Facility [Line Items]    
Total Commitment 0.0  
Lenders under loans 0.0 110.8
Senior Notes | Senior Secured Notes due 2031    
Line of Credit Facility [Line Items]    
Debt instrument, unamortized discount (premium) and debt issuance costs, net 5.0 5.9
Senior Notes | Senior Secured Notes due 2032    
Line of Credit Facility [Line Items]    
Debt instrument, unamortized discount (premium) and debt issuance costs, net $ 9.0 $ 10.1