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Assets and Liabilities, at Fair Value - Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Millions | Sep. 30, 2023 | Sep. 30, 2022
--- | --- | ---
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Cash and cash equivalents | $ 5.8 | $ 805.7
Securities and other assets segregated under federal and other regulations | 2,426.3 | 3,267.2
Financial instruments owned | 5,044.8 | 4,167.3
Physical commodities inventory | 537.3 | 513.5
Financial instruments sold, not yet purchased, at fair value | 3,085.6 | 2,469.6
Accounts payable and other accrued liabilities | 533.0 | 400.6
Fair Value, Measurements, Recurring |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Cash and cash equivalents | 66.5 | 43.5
Securities and other assets segregated under federal and other regulations | 5.8 | 805.7
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 4,248.3 | 2,817.2
Receivable from clients, net - Derivatives | (7.9) | (0.5)
Financial instruments owned | 5,044.8 | 4,167.3
Total assets at fair value | 9,744.0 | 8,193.0
Payables to clients - Derivatives | 79.8 | (1,392.4)
Total liabilities at fair value | 3,177.1 | 1,133.0
Fair Value, Measurements, 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, Measurements, 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 | 16.1 | 58.0
Fair Value, Measurements, Recurring | Derivatives |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Payable to broker-dealers, clearing organizations and counterparties | (5.9) | (2.2)
Fair Value, Measurements, 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 | 10.2 | 55.8
Fair Value, Measurements, Recurring | Physical commodities inventory |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Physical commodities inventory | 386.5 | 359.8
Fair Value, Measurements, Recurring | Equity securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 334.3 | 379.7
Financial instruments sold, not yet purchased, at fair value | 236.1 | 305.6
Fair Value, Measurements, Recurring | Corporate and municipal bonds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 284.2 | 156.8
Financial instruments sold, not yet purchased, at fair value | 81.6 | 63.2
Fair Value, Measurements, Recurring | U.S. Treasury obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 531.7 | 347.6
Financial instruments sold, not yet purchased, at fair value | 2,409.3 | 1,686.5
Fair Value, Measurements, Recurring | U.S. government agency obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 451.7 | 343.0
Financial instruments sold, not yet purchased, at fair value | 5.1 | 24.3
Fair Value, Measurements, Recurring | Foreign government obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 43.3 | 4.8
Financial instruments sold, not yet purchased, at fair value | 21.5 | 0.5
Fair Value, Measurements, Recurring | Agency mortgage-backed obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 2,865.8 | 2,588.7
Financial instruments sold, not yet purchased, at fair value | 31.7 | 5.4
Fair Value, Measurements, Recurring | Asset-backed obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 138.8 | 70.7
Fair Value, Measurements, Recurring | Derivatives |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 268.5 | 192.6
Financial instruments sold, not yet purchased, at fair value | 261.2 | 313.4
Fair Value, Measurements, Recurring | Commodities leases |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 16.0 | 26.4
Financial instruments sold, not yet purchased, at fair value |  | 0.0
Fair Value, Measurements, Recurring | Commodities warehouse receipts |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 54.7 | 24.9
Fair Value, Measurements, Recurring | Exchange firm common stock |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 12.0 | 10.6
Fair Value, Measurements, Recurring | Mutual funds and other |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 42.1 | 21.5
Fair Value, Measurements, Recurring | Cash flow hedges |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 1.7 |
Financial instruments sold, not yet purchased, at fair value | 27.1 | 70.6
Fair Value, Measurements, Recurring | Other |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments sold, not yet purchased, at fair value | 12.0 |
Fair Value, Measurements, 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 | 41.8 | 116.2
Fair Value, Measurements, 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 | 17.8 | 14.4
Fair Value, Measurements, 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 | 4,023.8 | 4,258.5
Fair Value, Measurements, 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 | 164.9 | (1,571.9)
Fair Value, Measurements, 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 | 5.8 | 19.7
Fair Value, Measurements, Recurring | U.S. Treasury obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Securities and other assets segregated under federal and other regulations |  | 786.0
Fair Value, Measurements, Recurring | Certificates of deposit |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets | 8.7 | 4.0
Fair Value, Measurements, Recurring | Money market mutual funds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets | 57.8 | 39.5
Fair Value, Measurements, 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 | (6,500.2) | (9,839.1)
Receivable from clients, net - Derivatives | (630.9) | (579.3)
Financial instruments owned | (600.2) | (502.4)
Total assets at fair value | (7,731.3) | (10,920.8)
Payables to clients - Derivatives | (5,577.1) | (9,290.3)
Financial instruments sold, not yet purchased, at fair value | (510.4) | (466.3)
Total liabilities at fair value | (7,639.0) | (10,505.0)
Fair Value, Measurements, 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, Measurements, 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 | (31.4) | (96.9)
Fair Value, Measurements, Recurring | Netting | Derivatives |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Payable to broker-dealers, clearing organizations and counterparties | (1,520.1) | (651.5)
Fair Value, Measurements, 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 | (1,551.5) | (748.4)
Fair Value, Measurements, 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, Measurements, 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, Measurements, 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, Measurements, 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, Measurements, 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, Measurements, 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, Measurements, 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, Measurements, 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, Measurements, Recurring | Netting | Derivatives |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | (600.2) | (502.4)
Financial instruments sold, not yet purchased, at fair value | (510.4) | (466.3)
Fair Value, Measurements, 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
Fair Value, Measurements, 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, Measurements, 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, Measurements, 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, Measurements, Recurring | Netting | Cash flow hedges |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 |
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0
Fair Value, Measurements, 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 |
Fair Value, Measurements, 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 | (31.7) | (91.4)
Fair Value, Measurements, 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, Measurements, 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, Measurements, 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 | (6,468.5) | (9,747.7)
Fair Value, Measurements, 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, Measurements, Recurring | Netting | U.S. Treasury obligations |  |
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
Fair Value, Measurements, 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, Measurements, 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, Measurements, Recurring | Level 1 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Cash and cash equivalents | 66.5 | 43.5
Securities and other assets segregated under federal and other regulations | 5.8 | 805.7
Deposits with and receivables from broker-dealers, clearing organizations and counterparties, net | 9,539.1 | 11,987.3
Receivable from clients, net - Derivatives | 61.7 | 67.2
Financial instruments owned | 1,005.6 | 773.9
Total assets at fair value | 10,919.0 | 13,813.9
Payables to clients - Derivatives | 5,430.7 | 7,722.5
Financial instruments sold, not yet purchased, at fair value | 2,663.8 | 1,986.9
Total liabilities at fair value | 8,206.7 | 9,768.1
Fair Value, Measurements, 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, Measurements, 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, Measurements, 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 | 112.2 | 58.7
Fair Value, Measurements, 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 | 112.2 | 58.7
Fair Value, Measurements, Recurring | Level 1 | Physical commodities inventory |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Physical commodities inventory | 240.3 | 136.3
Fair Value, Measurements, Recurring | Level 1 | Equity securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 324.0 | 367.9
Financial instruments sold, not yet purchased, at fair value | 230.6 | 299.9
Fair Value, Measurements, 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, Measurements, Recurring | Level 1 | U.S. Treasury obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 531.7 | 347.6
Financial instruments sold, not yet purchased, at fair value | 2,409.3 | 1,686.5
Fair Value, Measurements, 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, Measurements, Recurring | Level 1 | Foreign government obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 43.3 | 4.8
Financial instruments sold, not yet purchased, at fair value | 21.5 | 0.5
Fair Value, Measurements, 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, Measurements, 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, Measurements, 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 | 2.4 | 0.0
Fair Value, Measurements, 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
Fair Value, Measurements, Recurring | Level 1 | Commodities warehouse receipts |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 54.7 | 24.9
Fair Value, Measurements, Recurring | Level 1 | Exchange firm common stock |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 12.0 | 10.6
Fair Value, Measurements, Recurring | Level 1 | Mutual funds and other |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 39.3 | 17.4
Fair Value, Measurements, Recurring | Level 1 | Cash flow hedges |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 |
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0
Fair Value, Measurements, Recurring | Level 1 | 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 |
Fair Value, Measurements, 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, Measurements, 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 | 17.8 | 14.4
Fair Value, Measurements, 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 | 4,023.8 | 4,258.5
Fair Value, Measurements, 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 | 5,497.5 | 7,714.4
Fair Value, Measurements, 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 | 5.8 | 19.7
Fair Value, Measurements, Recurring | Level 1 | U.S. Treasury obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Securities and other assets segregated under federal and other regulations |  | 786.0
Fair Value, Measurements, Recurring | Level 1 | Certificates of deposit |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets | 8.7 | 4.0
Fair Value, Measurements, Recurring | Level 1 | Money market mutual funds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Assets | 57.8 | 39.5
Fair Value, Measurements, 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 | 1,209.4 | 669.0
Receivable from clients, net - Derivatives | 561.3 | 511.6
Financial instruments owned | 4,636.6 | 3,895.8
Total assets at fair value | 6,553.5 | 5,299.9
Payables to clients - Derivatives | 226.2 | 175.4
Financial instruments sold, not yet purchased, at fair value | 931.1 | 949.0
Total liabilities at fair value | 2,606.8 | 1,869.9
Fair Value, Measurements, 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, Measurements, 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 | 47.5 | 154.9
Fair Value, Measurements, 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 | 1,402.0 | 590.6
Fair Value, Measurements, 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 | 1,449.5 | 745.5
Fair Value, Measurements, Recurring | Level 2 | Physical commodities inventory |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Physical commodities inventory | 146.2 | 223.5
Fair Value, Measurements, Recurring | Level 2 | Equity securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 10.3 | 11.8
Financial instruments sold, not yet purchased, at fair value | 5.5 | 5.7
Fair Value, Measurements, Recurring | Level 2 | Corporate and municipal bonds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 284.2 | 156.8
Financial instruments sold, not yet purchased, at fair value | 81.6 | 63.2
Fair Value, Measurements, 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, Measurements, Recurring | Level 2 | U.S. government agency obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 451.7 | 343.0
Financial instruments sold, not yet purchased, at fair value | 5.1 | 24.3
Fair Value, Measurements, 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, at fair value | 0.0 | 0.0
Fair Value, Measurements, Recurring | Level 2 | Agency mortgage-backed obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 2,865.8 | 2,588.7
Financial instruments sold, not yet purchased, at fair value | 31.7 | 5.4
Fair Value, Measurements, Recurring | Level 2 | Asset-backed obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 138.8 | 70.7
Fair Value, Measurements, Recurring | Level 2 | Derivatives |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 868.1 | 694.3
Financial instruments sold, not yet purchased, at fair value | 769.2 | 779.7
Fair Value, Measurements, Recurring | Level 2 | Commodities leases |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 16.0 | 26.4
Financial instruments sold, not yet purchased, at fair value |  | 0.0
Fair Value, Measurements, 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, Measurements, 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, Measurements, 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 | 4.1
Fair Value, Measurements, Recurring | Level 2 | Cash flow hedges |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 1.7 |
Financial instruments sold, not yet purchased, at fair value | 27.1 | 70.6
Fair Value, Measurements, Recurring | Level 2 | Other |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments sold, not yet purchased, at fair value | 10.9 |
Fair Value, Measurements, 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 | 73.5 | 207.6
Fair Value, Measurements, 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, Measurements, 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, Measurements, 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 | 1,135.9 | 461.4
Fair Value, Measurements, 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, Measurements, Recurring | Level 2 | U.S. Treasury obligations |  |
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
Fair Value, Measurements, 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, Measurements, 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, Measurements, 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
Receivable from clients, net - Derivatives |  |
Financial instruments owned | 2.8 | 0.0
Total assets at fair value | 2.8 | 0.0
Payables to clients - Derivatives | 0.0 | 0.0
Financial instruments sold, not yet purchased, at fair value | 1.1 | 0.0
Total liabilities at fair value | 2.6 | 0.0
Fair Value, Measurements, 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, Measurements, 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, Measurements, 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, Measurements, 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, Measurements, 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, Measurements, 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, Measurements, 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, Measurements, 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, Measurements, 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, Measurements, 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, at fair value | 0.0 | 0.0
Fair Value, Measurements, 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, Measurements, 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, Measurements, 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, Measurements, 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
Fair Value, Measurements, 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, Measurements, 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, Measurements, 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 | 0.0
Fair Value, Measurements, Recurring | Level 3 | Cash flow hedges |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Financial instruments owned | 0.0 |
Financial instruments sold, not yet purchased, at fair value | 0.0 | 0.0
Fair Value, Measurements, Recurring | Level 3 | 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 |
Fair Value, Measurements, 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, Measurements, 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, Measurements, 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, Measurements, 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, Measurements, 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, Measurements, Recurring | Level 3 | U.S. Treasury obligations |  |
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
Fair Value, Measurements, 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, Measurements, 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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