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Assets and Liabilities, at Fair Value - Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Millions | Dec. 31, 2023 | Sep. 30, 2023
--- | --- | ---
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Cash and cash equivalents | $ 3.5 | $ 5.8
Securities and other assets segregated under federal and other regulations | 2,774.6 | 2,426.3
Financial instruments owned | 5,064.4 | 5,044.8
Physical commodities inventory | 518.4 | 537.3
Accounts payable and other accrued liabilities | 446.3 | 533.0
Financial instruments sold, not yet purchased | 2,748.0 | 3,085.6
Fair Value, Recurring |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Cash and cash equivalents | 62.7 | 66.5
Securities and other assets segregated under federal and other regulations | 3.5 | 5.8
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 3,769.3 | 4,248.3
Receivables from clients, net - Derivatives | 1.1 | (7.9)
Financial instruments owned | 5,064.4 | 5,044.8
Total assets at fair value | 9,215.4 | 9,744.0
Accounts payable and other accrued liabilities | 1.6 |
Payables to clients - Derivatives | 453.0 | 79.8
Total liabilities at fair value | 3,254.1 | 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 | To be announced 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 | 51.8 | 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 | (0.3) | (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 | 51.5 | 10.2
Fair Value, Recurring | Physical commodities inventory |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Physical commodities inventory | 314.4 | 386.5
Fair Value, Recurring | Equity securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 432.6 | 334.3
Financial instruments sold, not yet purchased | 323.8 | 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 | 208.4 | 284.2
Financial instruments sold, not yet purchased | 117.0 | 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 | 735.8 | 531.7
Financial instruments sold, not yet purchased | 2,003.5 | 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 | 132.0 | 451.7
Financial instruments sold, not yet purchased | 23.8 | 5.1
Fair Value, Recurring | Foreign government obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 26.0 | 43.3
Financial instruments sold, not yet purchased | 32.6 | 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 | 3,056.8 | 2,865.8
Financial instruments sold, not yet purchased | 0.6 | 31.7
Fair Value, Recurring | Asset-backed obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 107.5 | 138.8
Fair Value, Recurring | Derivatives |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 233.2 | 268.5
Financial instruments sold, not yet purchased | 237.5 | 261.2
Fair Value, Recurring | Commodities leases |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 16.6 | 16.0
Fair Value, Recurring | Commodities warehouse receipts |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 66.3 | 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 | 12.6 | 12.0
Fair Value, Recurring | Cash flow hedges |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 10.2 | 1.7
Financial instruments sold, not yet purchased | 8.0 | 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 | 26.4 | 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 | 1.2 | 12.0
Fair Value, Recurring | To be announced 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 | 6.6 | 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 | 19.1 | 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 | 3,245.0 | 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 | 498.6 | 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 | 3.5 | 5.8
Fair Value, Recurring | Certificates of deposit |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets | 12.3 | 8.7
Fair Value, Recurring | Money market mutual funds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets | 50.4 | 57.8
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 | (5,355.3) | (6,500.2)
Receivables from clients, net - Derivatives | (486.7) | (630.9)
Financial instruments owned | (794.9) | (600.2)
Total assets at fair value | (6,636.9) | (7,731.3)
Accounts payable and other accrued liabilities | 0.0 |
Payables to clients - Derivatives | (4,334.5) | (5,577.1)
Financial instruments sold, not yet purchased | (635.7) | (510.4)
Total liabilities at fair value | (6,477.7) | (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 | To be announced 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 | (19.5) | (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 | (1,488.0) | (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 | (1,507.5) | (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 | 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 | 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 | 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 | 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 | 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 | 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
Fair Value, Recurring | Netting | Derivatives |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | (794.9) | (600.2)
Financial instruments sold, not yet purchased | (635.7) | (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 | 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 | 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 | 0.0 | 0.0
Fair Value, Recurring | Netting | To be announced 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 | (19.5) | (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 | (5,335.8) | (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
Fair Value, Recurring | Netting | Certificates of deposit |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets | 0.0 | 0.0
Fair Value, Recurring | Netting | Money market mutual funds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets | 0.0 | 0.0
Fair Value, Recurring | Level 1 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Cash and cash equivalents | 62.7 | 66.5
Securities and other assets segregated under federal and other regulations | 3.5 | 5.8
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 7,939.4 | 9,539.1
Receivables from clients, net - Derivatives | 71.9 | 61.7
Financial instruments owned | 1,286.9 | 1,005.6
Total assets at fair value | 9,539.0 | 10,919.0
Accounts payable and other accrued liabilities | 0.0 |
Payables to clients - Derivatives | 4,640.3 | 5,430.7
Financial instruments sold, not yet purchased | 2,361.3 | 2,663.8
Total liabilities at fair value | 7,094.2 | 8,206.7
Fair Value, Recurring | Level 1 | 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 | Level 1 | To be announced 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
Fair Value, Recurring | Level 1 | Derivatives |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Payable to broker-dealers, clearing organizations and counterparties | 92.6 | 112.2
Fair Value, Recurring | Level 1 | 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 | 92.6 | 112.2
Fair Value, Recurring | Level 1 | Physical commodities inventory |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Physical commodities inventory | 174.6 | 240.3
Fair Value, Recurring | Level 1 | Equity securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 422.1 | 324.0
Financial instruments sold, not yet purchased | 318.7 | 230.6
Fair Value, Recurring | Level 1 | 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 | 0.0 | 0.0
Fair Value, Recurring | Level 1 | U.S. Treasury obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 735.8 | 531.7
Financial instruments sold, not yet purchased | 2,003.5 | 2,409.3
Fair Value, Recurring | Level 1 | 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 | 0.0 | 0.0
Fair Value, Recurring | Level 1 | Foreign government obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 26.0 | 43.3
Financial instruments sold, not yet purchased | 32.6 | 21.5
Fair Value, Recurring | Level 1 | 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 | 0.0 | 0.0
Fair Value, Recurring | Level 1 | Asset-backed obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Fair Value, Recurring | Level 1 | Derivatives |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.5 | 0.6
Financial instruments sold, not yet purchased | 6.5 | 2.4
Fair Value, Recurring | Level 1 | Commodities leases |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Fair Value, Recurring | Level 1 | Commodities warehouse receipts |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 66.3 | 54.7
Fair Value, Recurring | Level 1 | Exchange firm common stock |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 12.6 | 12.0
Fair Value, Recurring | Level 1 | 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 | 0.0 | 0.0
Fair Value, Recurring | Level 1 | Mutual funds and other |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 23.6 | 39.3
Fair Value, Recurring | Level 1 | Other |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments sold, not yet purchased | 0.0 | 0.0
Fair Value, Recurring | Level 1 | To be announced 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
Fair Value, Recurring | Level 1 | 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 | 19.1 | 17.8
Fair Value, Recurring | Level 1 | 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 | 3,245.0 | 4,023.8
Fair Value, Recurring | Level 1 | 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 | 4,675.3 | 5,497.5
Fair Value, Recurring | Level 1 | 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 | 3.5 | 5.8
Fair Value, Recurring | Level 1 | Certificates of deposit |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets | 12.3 | 8.7
Fair Value, Recurring | Level 1 | Money market mutual funds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets | 50.4 | 57.8
Fair Value, Recurring | Level 2 |  |
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 | 1,185.2 | 1,209.4
Receivables from clients, net - Derivatives | 415.9 | 561.3
Financial instruments owned | 4,569.6 | 4,636.6
Total assets at fair value | 6,310.5 | 6,553.5
Accounts payable and other accrued liabilities | 0.0 |
Payables to clients - Derivatives | 147.2 | 226.2
Financial instruments sold, not yet purchased | 1,021.2 | 931.1
Total liabilities at fair value | 2,634.8 | 2,606.8
Fair Value, Recurring | Level 2 | 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 | Level 2 | To be announced 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 | 71.3 | 47.5
Fair Value, Recurring | Level 2 | Derivatives |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Payable to broker-dealers, clearing organizations and counterparties | 1,395.1 | 1,402.0
Fair Value, Recurring | Level 2 | 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 | 1,466.4 | 1,449.5
Fair Value, Recurring | Level 2 | Physical commodities inventory |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Physical commodities inventory | 139.8 | 146.2
Fair Value, Recurring | Level 2 | Equity securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 10.5 | 10.3
Financial instruments sold, not yet purchased | 5.1 | 5.5
Fair Value, Recurring | Level 2 | Corporate and municipal bonds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 208.4 | 284.2
Financial instruments sold, not yet purchased | 117.0 | 81.6
Fair Value, Recurring | Level 2 | 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 | 0.0 | 0.0
Fair Value, Recurring | Level 2 | U.S. government agency obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 132.0 | 451.7
Financial instruments sold, not yet purchased | 23.8 | 5.1
Fair Value, Recurring | Level 2 | 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 | 0.0 | 0.0
Fair Value, Recurring | Level 2 | Agency mortgage-backed obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 3,056.8 | 2,865.8
Financial instruments sold, not yet purchased | 0.6 | 31.7
Fair Value, Recurring | Level 2 | Asset-backed obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 107.5 | 138.8
Fair Value, Recurring | Level 2 | Derivatives |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 1,027.6 | 868.1
Financial instruments sold, not yet purchased | 866.7 | 769.2
Fair Value, Recurring | Level 2 | Commodities leases |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 16.6 | 16.0
Fair Value, Recurring | Level 2 | 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 | Level 2 | 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 | Level 2 | Cash flow hedges |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 10.2 | 1.7
Financial instruments sold, not yet purchased | 8.0 | 27.1
Fair Value, Recurring | Level 2 | 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 | Level 2 | Other |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments sold, not yet purchased | 0.0 | 10.9
Fair Value, Recurring | Level 2 | To be announced 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 | 26.1 | 73.5
Fair Value, Recurring | Level 2 | 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 | Level 2 | 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 | Level 2 | 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 | 1,159.1 | 1,135.9
Fair Value, Recurring | Level 2 | 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
Fair Value, Recurring | Level 2 | Certificates of deposit |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets | 0.0 | 0.0
Fair Value, Recurring | Level 2 | Money market mutual funds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets | 0.0 | 0.0
Fair Value, Recurring | Level 3 |  |
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 | 1.6 |
Payables to clients - Derivatives | 0.0 |
Financial instruments sold, not yet purchased | 1.2 | 1.1
Total liabilities at fair value | 2.8 | 2.6
Fair Value, Recurring | Level 3 | 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 | Level 3 | To be announced 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
Fair Value, Recurring | Level 3 | 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
Fair Value, Recurring | Level 3 | 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
Fair Value, Recurring | Level 3 | 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 | Level 3 | 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 | 0.0 | 0.0
Fair Value, Recurring | Level 3 | 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 | 0.0 | 0.0
Fair Value, Recurring | Level 3 | 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 | 0.0 | 0.0
Fair Value, Recurring | Level 3 | 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 | 0.0 | 0.0
Fair Value, Recurring | Level 3 | 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 | 0.0 | 0.0
Fair Value, Recurring | Level 3 | 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 | 0.0 | 0.0
Fair Value, Recurring | Level 3 | Asset-backed obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Fair Value, Recurring | Level 3 | 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 | 0.0 | 0.0
Fair Value, Recurring | Level 3 | Commodities leases |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 | 0.0
Fair Value, Recurring | Level 3 | 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 | Level 3 | 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 | Level 3 | 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 | 0.0 | 0.0
Fair Value, Recurring | Level 3 | Mutual funds and other |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 2.8 | 2.8
Fair Value, Recurring | Level 3 | Other |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments sold, not yet purchased | 1.2 | 1.1
Fair Value, Recurring | Level 3 | To be announced 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
Fair Value, Recurring | Level 3 | 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 | Level 3 | 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 | Level 3 | 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
Fair Value, Recurring | Level 3 | 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
Fair Value, Recurring | Level 3 | Certificates of deposit |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets | 0.0 | 0.0
Fair Value, Recurring | Level 3 | Money market mutual funds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets | $ 0.0 | $ 0.0

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