v3.26.1
Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Schedule of Gross Derivative Assets and Liabilities (Details)
contract in Millions, $ in Millions
Jun. 30, 2026
USD ($)
contract
Sep. 30, 2025
USD ($)
contract
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset $ 8,962.5 $ 7,987.4
Derivative liability, fair value, gross liability 9,553.6 8,461.7
Impact of netting and collateral asset (8,095.1) (7,621.7)
Impact of netting and collateral liability $ (8,051.6) $ (7,594.3)
Derivative, number of instruments held | contract 16.8 19.2
Balance Sheet Location [Axis]: srt:PayablesToBrokerDealersAndClearingOrganizations    
Derivatives, Fair Value [Line Items]    
Derivative, fair value, net $ 27.0 $ 38.4
Balance Sheet Location [Axis]: srt:PayablesToCustomers    
Derivatives, Fair Value [Line Items]    
Derivative, fair value, net 1,033.2 530.7
Balance Sheet Location [Axis]: us-gaap:FinancialInstrumentsOwnedAtFairValue    
Derivatives, Fair Value [Line Items]    
Derivative, fair value, net (236.4) (199.9)
Balance Sheet Location [Axis]: us-gaap:FinancialInstrumentsSoldNotYetPurchasedAtFairValue    
Derivatives, Fair Value [Line Items]    
Derivative, fair value, net 441.8 298.3
Balance Sheet Location [Axis]: us-gaap:ReceivablesFromBrokersDealersAndClearingOrganizations    
Derivatives, Fair Value [Line Items]    
Derivative, fair value, net (560.7) (107.7)
Balance Sheet Location [Axis]: us-gaap:ReceivablesFromCustomers    
Derivatives, Fair Value [Line Items]    
Derivative, fair value, net (70.3) (58.1)
Derivative contracts not accounted for as hedges    
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset 8,961.2 7,977.9
Derivative liability, fair value, gross liability 9,531.8 8,460.7
Derivative contracts designated as hedging instruments    
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset 1.3 9.5
Derivative liability, fair value, gross liability 21.8 1.0
Commodity derivatives | Exchange-traded | Derivative contracts not accounted for as hedges    
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset 4,221.1 2,487.3
Derivative liability, fair value, gross liability 4,105.0 2,528.6
Commodity derivatives | OTC | Derivative contracts not accounted for as hedges    
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset 2,589.5 3,580.7
Derivative liability, fair value, gross liability 3,333.7 3,517.4
Foreign exchange derivatives | Exchange-traded | Derivative contracts not accounted for as hedges    
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset 5.5 7.5
Derivative liability, fair value, gross liability 5.5 7.5
Foreign exchange derivatives | OTC | Derivative contracts not accounted for as hedges    
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset 349.0 749.5
Derivative liability, fair value, gross liability 308.3 1,264.0
Interest rate derivatives | Derivative contracts designated as hedging instruments    
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset 0.0 0.0
Derivative liability, fair value, gross liability 20.1 0.0
Interest rate derivatives | Exchange-traded | Derivative contracts not accounted for as hedges    
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset 870.1 361.2
Derivative liability, fair value, gross liability 873.2 367.4
Interest rate derivatives | OTC | Derivative contracts not accounted for as hedges    
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset 94.5 148.3
Derivative liability, fair value, gross liability 100.7 148.3
Equity index derivatives | Derivative contracts not accounted for as hedges    
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset 237.6 195.1
Derivative liability, fair value, gross liability 186.9 138.1
Equity index derivatives | Exchange-traded | Derivative contracts not accounted for as hedges    
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset 546.2 413.4
Derivative liability, fair value, gross liability 546.2 413.4
To be announced (“TBA”) and forward settling securities | Derivative contracts not accounted for as hedges    
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset 47.7 34.9
Derivative liability, fair value, gross liability 72.3 76.0
Foreign currency forward contracts | Derivative contracts designated as hedging instruments    
Derivatives, Fair Value [Line Items]    
Derivative asset, fair value, gross asset 1.3 9.5
Derivative liability, fair value, gross liability $ 1.7 $ 1.0