v3.26.1
Revenue from Contracts with Clients - Schedule of Revenue from Contracts with Clients (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer $ 815.1 $ 851.2 $ 3,398.3 $ 2,334.7
Principal gains, net 404.8 334.0 1,253.0 943.4
Interest income 614.3 442.7 1,773.3 1,209.9
Total revenues 40,193.0 34,828.8 124,983.8 99,654.8
Total operating revenues 1,468.0 1,024.3 4,473.0 2,924.6
United States        
Disaggregation of Revenue [Line Items]        
Total revenues 2,700.3 1,930.5 7,734.9 5,594.9
Total operating revenues 1,068.4 733.1 3,168.5 2,097.1
Europe        
Disaggregation of Revenue [Line Items]        
Total revenues 894.8 900.2 3,507.7 2,446.2
Total operating revenues 258.4 175.4 828.1 484.3
South America        
Disaggregation of Revenue [Line Items]        
Total revenues 191.6 106.5 570.8 411.5
Total operating revenues 50.1 46.2 138.0 131.2
Middle East and Asia        
Disaggregation of Revenue [Line Items]        
Total revenues 36,390.5 31,877.0 113,138.9 91,191.9
Total operating revenues 75.3 55.0 306.8 175.9
Other        
Disaggregation of Revenue [Line Items]        
Total revenues 15.8 14.6 31.5 10.3
Total operating revenues 15.8 14.6 31.6 36.1
Point-in-time        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 773.9 808.4 3,266.4 2,207.0
Time elapsed        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 41.2 42.8 131.9 127.7
Exchange-traded futures and options        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 178.1 72.8 539.2 207.0
OTC derivative brokerage        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 3.5 2.9 8.3 8.2
Equities and fixed income        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 46.7 16.5 121.0 46.6
Mutual funds        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 0.8 0.7 2.6 2.3
Insurance and annuity products        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 2.6 2.8 10.1 9.3
Other        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 0.8 0.3 1.7 1.1
Total sales-based commission        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 232.5 96.0 682.9 274.5
Mutual funds        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 3.6 3.3 10.8 10.2
Insurance and annuity products        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 4.0 3.9 12.3 11.9
Total trailing commission        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 7.6 7.2 23.1 22.1
Clearing fees        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 86.7 49.1 263.5 141.2
Trade conversion fees        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 4.7 2.5 10.8 8.1
Other        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 0.5 11.2 4.2 33.7
Total commission and clearing fees        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 332.0 166.0 984.5 479.6
Total revenues 332.0 166.0 984.5 479.6
Underwriting fees        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 15.8 0.3 36.3 0.8
Asset management fees        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 15.2 17.1 47.3 46.3
Advisory and consulting fees        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 8.8 7.8 31.7 25.6
Sweep program fees        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 9.6 10.7 29.8 33.7
Client account fees        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 14.9 7.4 54.6 20.1
Other        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 5.3 2.9 15.0 11.8
Total consulting, management, and account fees        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 69.6 46.2 214.7 138.3
Total revenues 69.6 46.2 214.7 138.3
Precious metals sales under ASC Topic 606        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 413.5 639.0 2,199.1 1,716.8
Physical precious metals under ASC Topic 815        
Disaggregation of Revenue [Line Items]        
Sales of physical commodities 36,646.7 32,102.3 114,278.5 91,857.9
Physical agricultural and energy products        
Disaggregation of Revenue [Line Items]        
Sales of physical commodities $ 1,712.1 $ 1,098.6 $ 4,280.7 $ 3,308.9
Revenue from Contract with Customer Benchmark | Customer Concentration Risk | Clients        
Disaggregation of Revenue [Line Items]        
Revenues from contracts with clients as a percentage of total revenues 2.00% 2.40% 2.70% 2.30%