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Assets and Liabilities, at Fair Value - Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Millions | Dec. 31, 2020 | Sep. 30, 2020 | Dec. 31, 2019 | Sep. 30, 2019
--- | --- | --- | --- | ---
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Assets | $ 1,033.7 | $ 952.6 | $ 338.9 |
Cash and cash equivalents | 2.0 | 2.6 |  |
Cash and securities segregated under federal and other regulation | 2,203.9 | 1,920.2 |  |
Financial instruments owned | 2,852.4 | 2,727.7 |  |
Physical commodities inventory | 439.1 | 281.1 |  |
Accounts payable and other accrued liabilities - contingent liabilities | 244.5 | 272.6 |  |
Payable to broker-dealers, clearing organizations and counterparties | 314.8 | 537.5 |  |
Financial instruments sold, not yet purchased, at fair value | 827.4 | 686.0 |  |
Fair Value, Recurring |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Cash and cash equivalents | 15.4 | 16.0 |  |
Cash and securities segregated under federal and other regulation | 2.0 | 2.6 |  |
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 1,193.9 | 1,775.8 |  |
Receivables from clients - Derivatives | 2.2 |  |  | $ 1.5
Financial instruments owned | 2,852.4 | 2,727.7 |  |
Total assets at fair value | 4,365.4 | 4,739.3 |  |
Payables to clients - Derivatives | (121.3) | (222.7) |  |
Total liabilities at fair value | 738.0 | 479.5 |  |
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 | 30.7 | 10.2 |  |
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 | (0.1) | 4.5 |  |
Fair Value, Recurring | Payables 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 | 30.6 | 14.7 |  |
Fair Value, Recurring | Contingent Consideration |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Accounts payable and other accrued liabilities - contingent liabilities | 1.3 | 1.5 |  |
Fair Value, Recurring | Physical commodities inventory |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Physical commodities inventory | 299.5 | 215.7 |  |
Fair Value, Recurring | Equity securities |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Financial instruments owned | 366.1 | 264.3 |  |
Financial instruments sold, not yet purchased, at fair value | 318.9 | 232.9 |  |
Fair Value, Recurring | Corporate and municipal bonds |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Financial instruments owned | 85.7 | 66.9 |  |
Financial instruments sold, not yet purchased, at fair value | 10.8 | 22.5 |  |
Fair Value, Recurring | U.S. Treasury obligations |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Financial instruments owned | 313.9 | 419.9 |  |
Financial instruments sold, not yet purchased, at fair value | 249.4 | 247.5 |  |
Fair Value, Recurring | U.S. government agency obligations |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Financial instruments owned | 298.3 | 293.4 |  |
Financial instruments sold, not yet purchased, at fair value | 3.5 | 0.1 |  |
Fair Value, Recurring | Foreign government obligations |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Financial instruments owned | 2.6 | 2.5 |  |
Fair Value, Recurring | Agency mortgage-backed obligations |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Financial instruments owned | 1,522.8 | 1,384.6 |  |
Financial instruments sold, not yet purchased, at fair value | 3.1 | 5.1 |  |
Fair Value, Recurring | Asset-backed obligations |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Financial instruments owned | 34.0 | 33.0 |  |
Fair Value, Recurring | Derivatives |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Financial instruments owned | 126.9 | 117.4 |  |
Financial instruments sold, not yet purchased, at fair value | 239.8 | 176.8 |  |
Fair Value, Recurring | Commodities leases |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Financial instruments owned | 27.3 | 24.9 |  |
Financial instruments sold, not yet purchased, at fair value | 1.9 | 1.1 |  |
Fair Value, Recurring | Commodities warehouse receipts |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Financial instruments owned | 55.0 | 103.2 |  |
Fair Value, Recurring | Exchange firm common stock |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Financial instruments owned | 11.0 | 10.1 |  |
Fair Value, Recurring | Mutual funds and other |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Financial instruments owned | 8.8 | 7.5 |  |
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 | 28.1 | 19.2 |  |
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 | 8.7 | 8.0 |  |
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 | 1,197.0 | 1,941.3 |  |
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 | (39.9) | (192.7) |  |
Fair Value, Recurring | Commodities warehouse receipts |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Cash and securities segregated under federal and other regulation | 1.8 | 2.4 |  |
Fair Value, Recurring | U.S. Treasury obligations |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Cash and securities segregated under federal and other regulation | 0.2 | 0.2 |  |
Fair Value, Recurring | Certificates of deposit |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Assets | 3.2 | 3.2 |  |
Fair Value, Recurring | Money market mutual funds |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Assets | 12.2 | 12.8 |  |
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 |  |
Cash and securities segregated under federal and other regulation | 0.0 | 0.0 |  |
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | (2,232.2) | (2,549.3) |  |
Receivables from clients - Derivatives | (349.7) |  |  | (234.1)
Financial instruments owned | (471.2) | (535.6) |  |
Total assets at fair value | (3,053.1) | (3,319.0) |  |
Payables to clients - Derivatives | (2,368.0) | (2,399.9) |  |
Financial instruments sold, not yet purchased, at fair value | (181.9) | (386.8) |  |
Total liabilities at fair value | (2,767.4) | (3,100.7) |  |
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 | (0.1) | (11.8) |  |
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 | (217.4) | (302.2) |  |
Fair Value, Recurring | Netting | Payables 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 | (217.5) | (314.0) |  |
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 - contingent liabilities | 0.0 | 0.0 |  |
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 |  |
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 |  |
Fair Value, Recurring | Netting | Derivatives |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Financial instruments owned | (471.2) | (535.6) |  |
Financial instruments sold, not yet purchased, at fair value | (181.9) | (386.8) |  |
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 |  |
Financial instruments sold, not yet purchased, at fair value | 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 | 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 | 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 | (0.1) | (11.8) |  |
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 | (2,232.1) | (2,537.5) |  |
Fair Value, Recurring | Netting | Commodities warehouse receipts |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Cash and securities segregated under federal and other regulation | 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] |  |  |  |
Cash and securities segregated under federal and other regulation | 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 | 15.4 | 16.0 |  |
Cash and securities segregated under federal and other regulation | 2.0 | 2.6 |  |
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 2,971.6 | 3,898.3 |  |
Receivables from clients - Derivatives | 0.0 |  |  | 0.0
Financial instruments owned | 747.9 | 798.8 |  |
Total assets at fair value | 3,758.0 | 4,742.5 |  |
Payables to clients - Derivatives | 1,759.8 | 2,000.8 |  |
Financial instruments sold, not yet purchased, at fair value | 566.6 | 465.5 |  |
Total liabilities at fair value | 2,326.4 | 2,466.3 |  |
Fair Value, Recurring | Level 1 | 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 |  |
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 | 0.0 | 0.0 |  |
Fair Value, Recurring | Level 1 | Payables 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 1 | Contingent Consideration |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Accounts payable and other accrued liabilities - contingent liabilities | 0.0 | 0.0 |  |
Fair Value, Recurring | Level 1 | Physical commodities inventory |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Physical commodities inventory | 21.1 | 26.8 |  |
Fair Value, Recurring | Level 1 | Equity securities |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Financial instruments owned | 356.0 | 254.9 |  |
Financial instruments sold, not yet purchased, at fair value | 317.2 | 218.0 |  |
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, at fair value | 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 | 313.9 | 419.9 |  |
Financial instruments sold, not yet purchased, at fair value | 249.4 | 247.5 |  |
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, at fair value | 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 | 2.6 | 2.5 |  |
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, at fair value | 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 | 0.6 | 0.7 |  |
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0 |  |
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 |  |
Financial instruments sold, not yet purchased, at fair value | 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 | 55.0 | 103.2 |  |
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 | 11.0 | 10.1 |  |
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 | 8.8 | 7.5 |  |
Fair Value, Recurring | Level 1 | 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 |  |
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 | 8.7 | 8.0 |  |
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 | 1,197.0 | 1,941.3 |  |
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 | 1,765.9 | 1,949.0 |  |
Fair Value, Recurring | Level 1 | Commodities warehouse receipts |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Cash and securities segregated under federal and other regulation | 1.8 | 2.4 |  |
Fair Value, Recurring | Level 1 | U.S. Treasury obligations |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Cash and securities segregated under federal and other regulation | 0.2 | 0.2 |  |
Fair Value, Recurring | Level 1 | Certificates of deposit |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Assets | 3.2 | 3.2 |  |
Fair Value, Recurring | Level 1 | Money market mutual funds |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Assets | 12.2 | 12.8 |  |
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 |  |
Cash and securities segregated under federal and other regulation | 0.0 | 0.0 |  |
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 454.5 | 426.8 |  |
Receivables from clients - Derivatives | 351.9 |  |  | 235.6
Financial instruments owned | 2,575.7 | 2,464.5 |  |
Total assets at fair value | 3,660.5 | 3,315.8 |  |
Payables to clients - Derivatives | 486.9 | 176.4 |  |
Financial instruments sold, not yet purchased, at fair value | 442.7 | 607.3 |  |
Total liabilities at fair value | 1,177.7 | 1,112.4 |  |
Fair Value, Recurring | Level 2 | 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 | 30.8 | 22.0 |  |
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 | 217.3 | 306.7 |  |
Fair Value, Recurring | Level 2 | Payables 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 | 248.1 | 328.7 |  |
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 - contingent liabilities | 0.0 | 0.0 |  |
Fair Value, Recurring | Level 2 | Physical commodities inventory |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Physical commodities inventory | 278.4 | 188.9 |  |
Fair Value, Recurring | Level 2 | Equity securities |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Financial instruments owned | 10.1 | 9.4 |  |
Financial instruments sold, not yet purchased, at fair value | 1.7 | 14.9 |  |
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 | 85.7 | 66.9 |  |
Financial instruments sold, not yet purchased, at fair value | 10.8 | 22.5 |  |
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, at fair value | 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 | 298.3 | 293.4 |  |
Financial instruments sold, not yet purchased, at fair value | 3.5 | 0.1 |  |
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 |  |
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 | 1,522.8 | 1,384.6 |  |
Financial instruments sold, not yet purchased, at fair value | 3.1 | 5.1 |  |
Fair Value, Recurring | Level 2 | Asset-backed obligations |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Financial instruments owned | 34.0 | 33.0 |  |
Fair Value, Recurring | Level 2 | Derivatives |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Financial instruments owned | 597.5 | 652.3 |  |
Financial instruments sold, not yet purchased, at fair value | 421.7 | 563.6 |  |
Fair Value, Recurring | Level 2 | Commodities leases |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Financial instruments owned | 27.3 | 24.9 |  |
Financial instruments sold, not yet purchased, at fair value | 1.9 | 1.1 |  |
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 | 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 | 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 | 28.2 | 31.0 |  |
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 | 426.3 | 395.8 |  |
Fair Value, Recurring | Level 2 | Commodities warehouse receipts |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Cash and securities segregated under federal and other regulation | 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] |  |  |  |
Cash and securities segregated under federal and other regulation | 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 |  |
Cash and securities segregated under federal and other regulation | 0.0 | 0.0 |  |
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 0.0 | 0.0 |  |
Receivables from clients - Derivatives |  |  |  |
Financial instruments owned | 0.0 | 0.0 |  |
Total assets at fair value | 0.0 | 0.0 |  |
Payables to clients - Derivatives |  |  |  |
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0 |  |
Total liabilities at fair value | 1.3 | 1.5 |  |
Fair Value, Recurring | Level 3 | 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 |  |
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 | Payables 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 | Contingent Consideration |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Accounts payable and other accrued liabilities - contingent liabilities | 1.3 | 1.5 |  |
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, at fair value | 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, at fair value | 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, at fair value | 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, at fair value | 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 |  |
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, at fair value | 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, at fair value | 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 |  |
Financial instruments sold, not yet purchased, at fair value | 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 | 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 3 | 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 |  |
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] |  |  |  |
Cash and securities segregated under federal and other regulation | 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] |  |  |  |
Cash and securities segregated under federal and other regulation | 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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