XML 57 R45.htm IDEA: XBRL DOCUMENT
v3.24.2.u1

Assets and Liabilities, at Fair Value - Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Millions | Jun. 30, 2024 | Sep. 30, 2023
--- | --- | ---
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Cash and cash equivalents | $ 48.4 | $ 5.8
Securities and other assets segregated under federal and other regulations | 2,750.4 | 2,426.3
Financial instruments owned | 6,155.4 | 5,044.8
Physical commodities inventory | 587.4 | 537.3
Accounts payable and other accrued liabilities | 544.9 | 533.0
Financial instruments sold, not yet purchased, at fair value | 3,569.8 | 3,085.6
Fair Value, Recurring |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Cash and cash equivalents | 48.0 | 66.5
Securities and other assets segregated under federal and other regulations | 48.4 | 5.8
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 3,740.4 | 4,248.3
Receivables from clients, net - Derivatives | (0.5) | (7.9)
Financial instruments owned | 6,155.4 | 5,044.8
Total assets at fair value | 10,336.2 | 9,744.0
Accounts payable and other accrued liabilities | 1.7 |
Payables to clients - Derivatives | 387.3 | 79.8
Total liabilities at fair value | 3,962.4 | 3,177.1
Fair Value, Recurring | Contingent Consideration |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Accounts payable and other accrued liabilities |  | 1.5
Fair Value, Recurring | TBA and forward settling securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Payable to broker-dealers, clearing organizations and counterparties | 6.0 | 16.1
Fair Value, Recurring | Derivatives |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Payable to broker-dealers, clearing organizations and counterparties | (2.4) | (5.9)
Fair Value, Recurring | Payable to broker-dealers, clearing organizations and counterparties |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Payable to broker-dealers, clearing organizations and counterparties | 3.6 | 10.2
Fair Value, Recurring | Physical commodities inventory |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Physical commodities inventory | 344.5 | 386.5
Fair Value, Recurring | Equity securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 456.7 | 334.3
Financial instruments sold, not yet purchased, at fair value | 277.1 | 236.1
Fair Value, Recurring | Corporate and municipal bonds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 361.1 | 284.2
Financial instruments sold, not yet purchased, at fair value | 141.3 | 81.6
Fair Value, Recurring | U.S. Treasury obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 721.8 | 531.7
Financial instruments sold, not yet purchased, at fair value | 2,662.3 | 2,409.3
Fair Value, Recurring | U.S. government agency obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 373.9 | 451.7
Financial instruments sold, not yet purchased, at fair value | 13.7 | 5.1
Fair Value, Recurring | Foreign government obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 150.5 | 43.3
Financial instruments sold, not yet purchased, at fair value | 130.6 | 21.5
Fair Value, Recurring | Agency mortgage-backed obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 3,469.7 | 2,865.8
Financial instruments sold, not yet purchased, at fair value | 12.1 | 31.7
Fair Value, Recurring | Asset-backed obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 219.4 | 138.8
Financial instruments sold, not yet purchased, at fair value | 4.0 |
Fair Value, Recurring | Derivatives |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 316.7 | 268.5
Financial instruments sold, not yet purchased, at fair value | 325.5 | 261.2
Fair Value, Recurring | Commodities leases |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned |  | 16.0
Fair Value, Recurring | Commodities warehouse receipts |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 43.0 | 54.7
Fair Value, Recurring | Exchange firm common stock |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 11.8 | 12.0
Fair Value, Recurring | Cash flow hedges |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 5.5 | 1.7
Financial instruments sold, not yet purchased, at fair value | 2.1 | 27.1
Fair Value, Recurring | Mutual funds and other |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 25.3 | 42.1
Fair Value, Recurring | Other |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments sold, not yet purchased, at fair value | 1.1 | 12.0
Fair Value, Recurring | TBA and forward settling securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 4.0 | 41.8
Fair Value, Recurring | Foreign government obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 17.3 | 17.8
Fair Value, Recurring | U.S. Treasury obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 3,227.7 | 4,023.8
Fair Value, Recurring | Derivatives |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 491.4 | 164.9
Fair Value, Recurring | Commodities warehouse receipts |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Securities and other assets segregated under federal and other regulations | 48.4 | 5.8
Fair Value, Recurring | Netting |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Cash and cash equivalents | 0.0 | 0.0
Securities and other assets segregated under federal and other regulations | 0.0 | 0.0
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | (5,989.3) | (6,500.2)
Receivables from clients, net - Derivatives | (692.0) | (630.9)
Financial instruments owned | (416.2) | (600.2)
Total assets at fair value | (7,097.5) | (7,731.3)
Accounts payable and other accrued liabilities | 0.0 |
Payables to clients - Derivatives | (4,323.7) | (5,577.1)
Financial instruments sold, not yet purchased, at fair value | (340.1) | (510.4)
Total liabilities at fair value | (7,021.8) | (7,639.0)
Fair Value, Recurring | Netting | Contingent Consideration |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Accounts payable and other accrued liabilities |  | 0.0
Fair Value, Recurring | Netting | TBA and forward settling securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Payable to broker-dealers, clearing organizations and counterparties | (20.2) | (31.4)
Fair Value, Recurring | Netting | Derivatives |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Payable to broker-dealers, clearing organizations and counterparties | (2,337.8) | (1,520.1)
Fair Value, Recurring | Netting | Payable to broker-dealers, clearing organizations and counterparties |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Payable to broker-dealers, clearing organizations and counterparties | (2,358.0) | (1,551.5)
Fair Value, Recurring | Netting | Physical commodities inventory |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Physical commodities inventory | 0.0 | 0.0
Fair Value, Recurring | Netting | Equity securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0
Fair Value, Recurring | Netting | Corporate and municipal bonds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0
Fair Value, Recurring | Netting | U.S. Treasury obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0
Fair Value, Recurring | Netting | U.S. government agency obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0
Fair Value, Recurring | Netting | Foreign government obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0
Fair Value, Recurring | Netting | Agency mortgage-backed obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0
Fair Value, Recurring | Netting | Asset-backed obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Financial instruments sold, not yet purchased, at fair value | 0.0 |
Fair Value, Recurring | Netting | Derivatives |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | (416.2) | (600.2)
Financial instruments sold, not yet purchased, at fair value | (340.1) | (510.4)
Fair Value, Recurring | Netting | Commodities leases |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned |  | 0.0
Fair Value, Recurring | Netting | Commodities warehouse receipts |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Fair Value, Recurring | Netting | Exchange firm common stock |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Fair Value, Recurring | Netting | Cash flow hedges |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0
Fair Value, Recurring | Netting | Mutual funds and other |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Fair Value, Recurring | Netting | Other |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0
Fair Value, Recurring | Netting | TBA and forward settling securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | (21.4) | (31.7)
Fair Value, Recurring | Netting | Foreign government obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 0.0 | 0.0
Fair Value, Recurring | Netting | U.S. Treasury obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 0.0 | 0.0
Fair Value, Recurring | Netting | Derivatives |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | (5,967.9) | (6,468.5)
Fair Value, Recurring | Netting | Commodities warehouse receipts |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Securities and other assets segregated under federal and other regulations | 0.0 | 0.0
Level 1 | Fair Value, Recurring |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Cash and cash equivalents | 48.0 | 66.5
Securities and other assets segregated under federal and other regulations | 48.4 | 5.8
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 7,955.5 | 9,539.1
Receivables from clients, net - Derivatives | 76.7 | 61.7
Financial instruments owned | 1,390.0 | 1,005.6
Total assets at fair value | 9,712.4 | 10,919.0
Accounts payable and other accrued liabilities | 0.0 |
Payables to clients - Derivatives | 4,418.5 | 5,430.7
Financial instruments sold, not yet purchased, at fair value | 3,070.7 | 2,663.8
Total liabilities at fair value | 7,860.8 | 8,206.7
Level 1 | Fair Value, Recurring | Contingent Consideration |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Accounts payable and other accrued liabilities |  | 0.0
Level 1 | Fair Value, Recurring | TBA and forward settling securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Payable to broker-dealers, clearing organizations and counterparties | 0.0 | 0.0
Level 1 | Fair Value, Recurring | Derivatives |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Payable to broker-dealers, clearing organizations and counterparties | 371.6 | 112.2
Level 1 | Fair Value, Recurring | Payable to broker-dealers, clearing organizations and counterparties |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Payable to broker-dealers, clearing organizations and counterparties | 371.6 | 112.2
Level 1 | Fair Value, Recurring | Physical commodities inventory |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Physical commodities inventory | 193.8 | 240.3
Level 1 | Fair Value, Recurring | Equity securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 440.3 | 324.0
Financial instruments sold, not yet purchased, at fair value | 272.0 | 230.6
Level 1 | Fair Value, Recurring | Corporate and municipal bonds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0
Level 1 | Fair Value, Recurring | U.S. Treasury obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 721.8 | 531.7
Financial instruments sold, not yet purchased, at fair value | 2,662.3 | 2,409.3
Level 1 | Fair Value, Recurring | U.S. government agency obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0
Level 1 | Fair Value, Recurring | Foreign government obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 150.5 | 43.3
Financial instruments sold, not yet purchased, at fair value | 130.6 | 21.5
Level 1 | Fair Value, Recurring | Agency mortgage-backed obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0
Level 1 | Fair Value, Recurring | Asset-backed obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Financial instruments sold, not yet purchased, at fair value | 0.0 |
Level 1 | Fair Value, Recurring | Derivatives |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.1 | 0.6
Financial instruments sold, not yet purchased, at fair value | 5.8 | 2.4
Level 1 | Fair Value, Recurring | Commodities leases |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned |  | 0.0
Level 1 | Fair Value, Recurring | Commodities warehouse receipts |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 43.0 | 54.7
Level 1 | Fair Value, Recurring | Exchange firm common stock |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 11.8 | 12.0
Level 1 | Fair Value, Recurring | Cash flow hedges |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0
Level 1 | Fair Value, Recurring | Mutual funds and other |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 22.5 | 39.3
Level 1 | Fair Value, Recurring | Other |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0
Level 1 | Fair Value, Recurring | TBA and forward settling securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 0.0 | 0.0
Level 1 | Fair Value, Recurring | Foreign government obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 17.3 | 17.8
Level 1 | Fair Value, Recurring | U.S. Treasury obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 3,227.7 | 4,023.8
Level 1 | Fair Value, Recurring | Derivatives |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 4,710.5 | 5,497.5
Level 1 | Fair Value, Recurring | Commodities warehouse receipts |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Securities and other assets segregated under federal and other regulations | 48.4 | 5.8
Level 2 | Fair Value, Recurring |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Cash and cash equivalents | 0.0 | 0.0
Securities and other assets segregated under federal and other regulations | 0.0 | 0.0
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 1,774.2 | 1,209.4
Receivables from clients, net - Derivatives | 614.8 | 561.3
Financial instruments owned | 5,178.8 | 4,636.6
Total assets at fair value | 7,718.5 | 6,553.5
Accounts payable and other accrued liabilities | 0.0 |
Payables to clients - Derivatives | 292.5 | 226.2
Financial instruments sold, not yet purchased, at fair value | 838.1 | 931.1
Total liabilities at fair value | 3,120.6 | 2,606.8
Level 2 | Fair Value, Recurring | Contingent Consideration |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Accounts payable and other accrued liabilities |  | 0.0
Level 2 | Fair Value, Recurring | TBA and forward settling securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Payable to broker-dealers, clearing organizations and counterparties | 26.2 | 47.5
Level 2 | Fair Value, Recurring | Derivatives |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Payable to broker-dealers, clearing organizations and counterparties | 1,963.8 | 1,402.0
Level 2 | Fair Value, Recurring | Payable to broker-dealers, clearing organizations and counterparties |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Payable to broker-dealers, clearing organizations and counterparties | 1,990.0 | 1,449.5
Level 2 | Fair Value, Recurring | Physical commodities inventory |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Physical commodities inventory | 150.7 | 146.2
Level 2 | Fair Value, Recurring | Equity securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 16.4 | 10.3
Financial instruments sold, not yet purchased, at fair value | 5.1 | 5.5
Level 2 | Fair Value, Recurring | Corporate and municipal bonds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 361.1 | 284.2
Financial instruments sold, not yet purchased, at fair value | 141.3 | 81.6
Level 2 | Fair Value, Recurring | U.S. Treasury obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0
Level 2 | Fair Value, Recurring | U.S. government agency obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 373.9 | 451.7
Financial instruments sold, not yet purchased, at fair value | 13.7 | 5.1
Level 2 | Fair Value, Recurring | Foreign government obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0
Level 2 | Fair Value, Recurring | Agency mortgage-backed obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 3,469.7 | 2,865.8
Financial instruments sold, not yet purchased, at fair value | 12.1 | 31.7
Level 2 | Fair Value, Recurring | Asset-backed obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 219.4 | 138.8
Financial instruments sold, not yet purchased, at fair value | 4.0 |
Level 2 | Fair Value, Recurring | Derivatives |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 732.8 | 868.1
Financial instruments sold, not yet purchased, at fair value | 659.8 | 769.2
Level 2 | Fair Value, Recurring | Commodities leases |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned |  | 16.0
Level 2 | Fair Value, Recurring | Commodities warehouse receipts |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Level 2 | Fair Value, Recurring | Exchange firm common stock |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Level 2 | Fair Value, Recurring | Cash flow hedges |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 5.5 | 1.7
Financial instruments sold, not yet purchased, at fair value | 2.1 | 27.1
Level 2 | Fair Value, Recurring | Mutual funds and other |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Level 2 | Fair Value, Recurring | Other |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments sold, not yet purchased, at fair value | 0.0 | 10.9
Level 2 | Fair Value, Recurring | TBA and forward settling securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 25.4 | 73.5
Level 2 | Fair Value, Recurring | Foreign government obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 0.0 | 0.0
Level 2 | Fair Value, Recurring | U.S. Treasury obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 0.0 | 0.0
Level 2 | Fair Value, Recurring | Derivatives |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 1,748.8 | 1,135.9
Level 2 | Fair Value, Recurring | Commodities warehouse receipts |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Securities and other assets segregated under federal and other regulations | 0.0 | 0.0
Level 3 | Fair Value, Recurring |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Cash and cash equivalents | 0.0 | 0.0
Securities and other assets segregated under federal and other regulations | 0.0 | 0.0
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 0.0 | 0.0
Receivables from clients, net - Derivatives | 0.0 |
Financial instruments owned | 2.8 | 2.8
Total assets at fair value | 2.8 | 2.8
Accounts payable and other accrued liabilities | 1.7 |
Payables to clients - Derivatives | 0.0 |
Financial instruments sold, not yet purchased, at fair value | 1.1 | 1.1
Total liabilities at fair value | 2.8 | 2.6
Level 3 | Fair Value, Recurring | Contingent Consideration |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Accounts payable and other accrued liabilities |  | 1.5
Level 3 | Fair Value, Recurring | TBA and forward settling securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Payable to broker-dealers, clearing organizations and counterparties | 0.0 | 0.0
Level 3 | Fair Value, Recurring | Derivatives |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Payable to broker-dealers, clearing organizations and counterparties | 0.0 | 0.0
Level 3 | Fair Value, Recurring | Payable to broker-dealers, clearing organizations and counterparties |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Payable to broker-dealers, clearing organizations and counterparties | 0.0 | 0.0
Level 3 | Fair Value, Recurring | Physical commodities inventory |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Physical commodities inventory | 0.0 | 0.0
Level 3 | Fair Value, Recurring | Equity securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0
Level 3 | Fair Value, Recurring | Corporate and municipal bonds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0
Level 3 | Fair Value, Recurring | U.S. Treasury obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0
Level 3 | Fair Value, Recurring | U.S. government agency obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0
Level 3 | Fair Value, Recurring | Foreign government obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0
Level 3 | Fair Value, Recurring | Agency mortgage-backed obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0
Level 3 | Fair Value, Recurring | Asset-backed obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Financial instruments sold, not yet purchased, at fair value | 0.0 |
Level 3 | Fair Value, Recurring | Derivatives |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0
Level 3 | Fair Value, Recurring | Commodities leases |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned |  | 0.0
Level 3 | Fair Value, Recurring | Commodities warehouse receipts |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Level 3 | Fair Value, Recurring | Exchange firm common stock |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Level 3 | Fair Value, Recurring | Cash flow hedges |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0
Level 3 | Fair Value, Recurring | Mutual funds and other |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 2.8 | 2.8
Level 3 | Fair Value, Recurring | Other |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments sold, not yet purchased, at fair value | 1.1 | 1.1
Level 3 | Fair Value, Recurring | TBA and forward settling securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 0.0 | 0.0
Level 3 | Fair Value, Recurring | Foreign government obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 0.0 | 0.0
Level 3 | Fair Value, Recurring | U.S. Treasury obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 0.0 | 0.0
Level 3 | Fair Value, Recurring | Derivatives |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 0.0 | 0.0
Level 3 | Fair Value, Recurring | Commodities warehouse receipts |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Securities and other assets segregated under federal and other regulations | 0.0 | 0.0
Certificates of deposit | Fair Value, Recurring |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets | 12.4 | 8.7
Certificates of deposit | Fair Value, Recurring | Netting |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets | 0.0 | 0.0
Certificates of deposit | Level 1 | Fair Value, Recurring |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets | 12.4 | 8.7
Certificates of deposit | Level 2 | Fair Value, Recurring |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets | 0.0 | 0.0
Certificates of deposit | Level 3 | Fair Value, Recurring |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets | 0.0 | 0.0
Money market mutual funds | Fair Value, Recurring |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets | 35.6 | 57.8
Money market mutual funds | Fair Value, Recurring | Netting |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets | 0.0 | 0.0
Money market mutual funds | Level 1 | Fair Value, Recurring |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets | 35.6 | 57.8
Money market mutual funds | Level 2 | Fair Value, Recurring |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets | 0.0 | 0.0
Money market mutual funds | Level 3 | Fair Value, Recurring |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets | $ 0.0 | $ 0.0

X
- Definition Accounts Payable Including Netting Adjustment, Fair Value Disclosure + References No definition available. + Details
Name: | intl_AccountsPayableIncludingNettingAdjustmentFairValueDisclosure
Namespace Prefix: | intl_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Accounts Receivable Including Netting Adjustment, Fair Value Disclosure + References No definition available. + Details
Name: | intl_AccountsReceivableIncludingNettingAdjustmentFairValueDisclosure
Namespace Prefix: | intl_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Broker-Dealer, Payable to Other Broker-Dealer and Clearing Organization Including Netting Adjustment + References No definition available. + Details
Name: | intl_BrokerDealerPayableToOtherBrokerDealerAndClearingOrganizationIncludingNettingAdjustment
Namespace Prefix: | intl_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Receivables from Clearing Organizations Including Netting Adjustment + References No definition available. + Details
Name: | intl_ReceivablesFromClearingOrganizationsIncludingNettingAdjustment
Namespace Prefix: | intl_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of liabilities incurred and payable to vendors for goods and services received, and accrued liabilities classified as other. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-04(10)(d)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479170/946-210-S99-1 + Details
Name: | us-gaap_AccountsPayableAndOtherAccruedLiabilities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Fair value portion of asset recognized for present right to economic benefit. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 100 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482078/820-10-55-100 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 + Details
Name: | us-gaap_AssetsFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Excludes cash and cash equivalents within disposal group and discontinued operation. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 852 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 10 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481372/852-10-55-10 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 946 -SubTopic 830 -Name Accounting Standards Codification -Section 55 -Paragraph 12 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479168/946-830-55-12 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(2)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-04(4)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479170/946-210-S99-1 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section 45 -Paragraph 21 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477796/946-210-45-21 Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(1)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Name Accounting Standards Codification -Section 45 -Paragraph 20 -SubTopic 210 -Topic 946 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477796/946-210-45-20 + Details
Name: | us-gaap_Cash
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 + Details
Name: | us-gaap_CashAndCashEquivalentsFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of cash subject to withdrawal restrictions, restricted deposits held as compensating balances, and cash and securities segregated in compliance with regulations (such as cash deposited in a special reserve account for the exclusive benefit of customers). + References No definition available. + Details
Name: | us-gaap_CashAndSecuritiesSegregatedUnderFederalAndOtherRegulations
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 100 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482078/820-10-55-100 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-3 + Details
Name: | us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The aggregate fair value as of the balance sheet date of financial instruments and other positions owned by the entity including: (1) mortgages, mortgage-backed and asset backed securities; (2) US government and agency obligations; (3) state and municipal government obligations; (4) other sovereign government debt; (5) corporate obligations; (6) corporate equities; (7) principal investments; (8) derivative contracts; and (9) physical commodities. Includes both pledged and unpledged holdings. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 940 -SubTopic 320 -Name Accounting Standards Codification -Section 45 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479035/940-320-45-2 + Details
Name: | us-gaap_FinancialInstrumentsOwnedAtFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of obligations incurred from short sales. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2E -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2E Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 940 -SubTopic 320 -Name Accounting Standards Codification -Section 45 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479035/940-320-45-2 + Details
Name: | us-gaap_FinancialInstrumentsSoldNotYetPurchasedAtFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Gross amount, as of the balance sheet date, of merchandise, goods, commodities, or supplies held for future sale or to be used in manufacturing, servicing or production process. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(6)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 + Details
Name: | us-gaap_InventoryGross
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of financial and nonfinancial obligations. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 + Details
Name: | us-gaap_LiabilitiesFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | intl_AccountsPayableAndOtherAccruedLiabilitiesIncludingContingentLiabilitiesAxis=intl_ContingentConsiderationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | intl_PayablesToBrokerDealersClearingOrganizationsAndCounterpartiesAxis=intl_TBAAndForwardSettlingSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | intl_PayablesToBrokerDealersClearingOrganizationsAndCounterpartiesAxis=us-gaap_DerivativeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | intl_PayablesToBrokerDealersClearingOrganizationsAndCounterpartiesAxis=intl_PayablesToBrokerDealersClearingOrganizationsAndCounterpartiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | intl_PhysicalCommoditiesInventoryAxis=intl_PhysicalCommoditiesInventoryPreciousMetalsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueAxis=us-gaap_EquitySecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueAxis=us-gaap_DebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueAxis=us-gaap_USGovernmentDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueAxis=us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueAxis=us-gaap_ForeignGovernmentDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueAxis=us-gaap_MortgageBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueAxis=us-gaap_DerivativeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueAxis=intl_CommoditiesLeasesAndUnpricedPositionsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueAxis=intl_CommoditiesWarehouseReceiptsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueAxis=intl_ExchangeFirmCommonStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueAxis=intl_CashFlowHedgesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueAxis=intl_MutualFundsAndOtherMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SecurityOwnedAndSoldNotYetPurchasedAtFairValueAxis=intl_OtherMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | intl_DepositsAndReceivablesFromBrokerDealersClearingOrganizationsAndCounterpartiesAxis=intl_TBAAndForwardSettlingSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | intl_DepositsAndReceivablesFromBrokerDealersClearingOrganizationsAndCounterpartiesAxis=us-gaap_ForeignGovernmentDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | intl_DepositsAndReceivablesFromExchangeClearingOrganizationsAxis=us-gaap_USGovernmentDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | intl_DepositsAndReceivablesFromExchangeClearingOrganizationsAxis=us-gaap_DerivativeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | intl_SecuritiesAndOtherAssetsSegregatedUnderFederalAndOtherRegulationsAxis=intl_CommoditiesWarehouseReceiptsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | intl_DerivativeNettingAdjustmentAxis=intl_CounterpartyAndCashCollateralNettingAdjustmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CashAndCashEquivalentsAxis=us-gaap_CertificatesOfDepositMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CashAndCashEquivalentsAxis=us-gaap_MoneyMarketFundsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |