v3.25.1
Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Gross Derivative Assets and Liabilities by Type and Balance Sheet Location (Details)
contract in Millions, $ in Millions
Mar. 31, 2025
USD ($)
contract
Sep. 30, 2024
USD ($)
contract
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset $ 6,149.0 $ 7,235.9
Derivative liability, fair value, gross liability 5,935.7 7,144.1
Impact of netting and collateral asset (6,006.0) (6,670.6)
Impact of netting and collateral liability $ (5,956.8) $ (6,614.6)
Derivative, number of instruments held | contract 12.8 12.2
Total fair value included in Deposits with and receivables from broker-dealers, clearing organizations, and counterparties, net    
Derivatives, Fair Value [Line Items]    
Derivative, fair value, net $ (72.4) $ 336.0
Total fair value included in Receivable from clients, net    
Derivatives, Fair Value [Line Items]    
Derivative, fair value, net 0.5 (8.4)
Total fair value included in Financial instruments owned, at fair value    
Derivatives, Fair Value [Line Items]    
Derivative, fair value, net 214.9 237.7
Total fair value included in Payables to clients    
Derivatives, Fair Value [Line Items]    
Derivative, fair value, net (215.4) 265.9
Total fair value included in Payables to broker-dealers, clearing organizations and counterparties    
Derivatives, Fair Value [Line Items]    
Derivative, fair value, net (11.2) (1.4)
Total fair value included in Financial instruments sold, not yet purchased, at fair value    
Derivatives, Fair Value [Line Items]    
Derivative, fair value, net 205.5 265.0
Not Designated as Hedging Instrument    
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset 6,139.9 7,226.3
Derivative liability, fair value, gross liability 5,935.5 7,143.9
Designated as Hedging Instrument    
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset 9.1 9.6
Derivative liability, fair value, gross liability 0.2 0.2
Exchange-traded commodity derivatives | Not Designated as Hedging Instrument    
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset 1,588.4 1,383.1
Derivative liability, fair value, gross liability 1,612.9 1,415.7
OTC commodity derivatives | Not Designated as Hedging Instrument    
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset 2,651.9 1,967.9
Derivative liability, fair value, gross liability 2,467.9 1,924.3
Exchange-traded foreign exchange derivatives | Not Designated as Hedging Instrument    
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset 4.2 2.0
Derivative liability, fair value, gross liability 4.2 2.0
OTC foreign exchange derivatives | Not Designated as Hedging Instrument    
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset 453.7 975.2
Derivative liability, fair value, gross liability 437.2 938.2
Exchange-traded interest rate derivatives | Not Designated as Hedging Instrument    
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset 656.6 720.1
Derivative liability, fair value, gross liability 658.7 728.1
OTC interest rate derivatives | Not Designated as Hedging Instrument    
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset 180.1 207.1
Derivative liability, fair value, gross liability 180.1 207.1
OTC interest rate derivatives | Designated as Hedging Instrument    
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset 0.0 0.0
Derivative liability, fair value, gross liability 0.0 0.2
Exchange-traded equity index derivatives | Not Designated as Hedging Instrument    
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset 381.6 1,817.4
Derivative liability, fair value, gross liability 381.6 1,817.4
OTC equity and indices derivatives | Not Designated as Hedging Instrument    
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset 201.4 127.4
Derivative liability, fair value, gross liability 171.2 86.7
TBA and forward settling securities | Not Designated as Hedging Instrument    
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset 22.0 26.1
Derivative liability, fair value, gross liability 21.7 24.4
Foreign currency forward contracts | Designated as Hedging Instrument    
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset 9.1 9.6
Derivative liability, fair value, gross liability $ 0.2 $ 0.0