v3.25.1
Revenue from Contracts with Clients - Revenue from Contracts with Clients (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Mar. 31, 2025
Mar. 31, 2024
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer $ 820.4 $ 509.2 $ 1,483.5 $ 1,136.6
Principal gains, net 300.5 281.8 609.4 575.6
Interest income 389.0 326.0 767.2 616.1
Total revenues 36,890.7 22,106.1 64,826.0 41,679.1
Total operating revenues 956.0 818.2 1,900.3 1,602.4
United States        
Disaggregation of Revenue [Line Items]        
Total revenues 1,880.0 1,407.7 3,664.4 3,011.2
Total operating revenues 728.6 590.0 1,364.0 1,158.0
Europe        
Disaggregation of Revenue [Line Items]        
Total revenues 840.2 560.2 1,546.0 1,218.6
Total operating revenues 102.7 161.1 308.9 296.7
South America        
Disaggregation of Revenue [Line Items]        
Total revenues 141.7 105.0 305.0 233.0
Total operating revenues 53.8 25.2 85.0 66.4
Middle East and Asia        
Disaggregation of Revenue [Line Items]        
Total revenues 34,024.2 20,025.1 59,314.9 37,200.7
Total operating revenues 59.6 33.7 120.9 65.7
Other        
Disaggregation of Revenue [Line Items]        
Total revenues 4.6 8.1 (4.3) 15.6
Total operating revenues 11.3 8.2 21.5 15.6
Point-in-time        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 777.9 469.7 1,398.6 1,059.4
Time elapsed        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 42.5 39.5 84.9 77.2
Exchange-traded futures and options        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 71.0 55.8 134.2 107.2
OTC derivative brokerage        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 2.5 3.0 5.3 5.8
Equities and fixed income        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 15.0 14.5 30.1 31.0
Mutual funds        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 0.8 0.9 1.6 1.6
Insurance and annuity products        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 3.3 3.7 6.5 5.7
Other        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 0.4 0.2 0.8 0.1
Total sales-based commission        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 93.0 78.1 178.5 151.4
Mutual funds        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 3.5 3.2 6.9 6.2
Insurance and annuity products        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 4.0 3.7 8.0 7.4
Total trailing commission        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 7.5 6.9 14.9 13.6
Clearing fees        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 48.0 45.4 92.1 88.7
Trade conversion fees        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 3.4 3.5 5.6 7.5
Other        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 12.4 2.3 22.5 4.7
Total commission and clearing fees        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 164.3 136.2 313.6 265.9
Total revenues 164.3 136.2 313.6 265.9
Underwriting fees        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 0.2 0.1 0.5 0.1
Asset management fees        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 14.4 12.3 29.2 23.7
Advisory and consulting fees        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 9.2 9.0 17.8 17.2
Sweep program fees        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 11.4 11.3 23.0 22.7
Client account fees        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 6.5 4.3 12.7 8.5
Other        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 2.6 3.2 8.9 6.5
Total consulting, management, and account fees        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 44.3 40.2 92.1 78.7
Total revenues 44.3 40.2 92.1 78.7
Precious metals sales under ASC Topic 606        
Disaggregation of Revenue [Line Items]        
Revenue from contract with customer 611.8 332.8 1,077.8 792.0
Physical precious metals under ASC Topic 815        
Disaggregation of Revenue [Line Items]        
Sales of physical commodities 34,233.2 20,067.0 59,755.6 37,229.5
Physical agricultural and energy products        
Disaggregation of Revenue [Line Items]        
Sales of physical commodities $ 1,147.6 $ 922.1 $ 2,210.3 $ 2,121.3
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 2.20% 2.30% 2.30% 2.70%