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Assets and Liabilities, at Fair Value - Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Millions | Sep. 30, 2017 | Sep. 30, 2016 | Sep. 30, 2015
--- | --- | --- | ---
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Cash and Securities Segregated under Federal and Other Regulations | $ 518.8 | $ 1,136.3 |
Receivables from Brokers-Dealers and Clearing Organizations | 2,625.1 | 1,761.4 |
Financial instruments owned, at fair value | 1,731.8 | 1,606.1 |
Assets, Fair Value Disclosure | 2,068.0 |  |
Accounts payable and other accrued liabilities | 135.6 | 161.3 |
Payables to Broker-Dealers and Clearing Organizations | (125.7) | (260.1) |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 717.6 | 839.4 |
Fair Value, Measurements, Recurring [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Cash and Cash Equivalents, Fair Value Disclosure |  | 7.1 |
Cash and Securities Segregated under Federal and Other Regulations | 54.5 | 618.8 |
Receivables from Exchange Clearing Organizations |  | 853.3 |
Receivables from Brokers-Dealers and Clearing Organizations | 204.7 |  |
Financial instruments owned, at fair value | 1,731.8 | 1,606.1 |
Assets, Fair Value Disclosure | 2,068.0 | 3,156.5 |
Payables to Broker-Dealers and Clearing Organizations | (4.8) |  |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 717.6 | 839.4 |
Liabilities, Fair Value Disclosure | 723.4 | 843.7 |
Fair Value, Measurements, Recurring [Member] | TBA and forward settling securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Payables to Broker-Dealers and Clearing Organizations | (4.8) | (3.5) |
Fair Value, Measurements, Recurring [Member] | Derivative [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Payables to Broker-Dealers and Clearing Organizations | 0.0 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Contingent Consideration [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Accounts payable and other accrued liabilities | 1.0 | 0.8 |
Fair Value, Measurements, Recurring [Member] | Physical commodities inventory[Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Physical Commodities Inventory | 73.2 | 71.2 |
Fair Value, Measurements, Recurring [Member] | Asset-backed Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 47.3 |  |
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 368.9 |  |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 27.9 |  |
Fair Value, Measurements, Recurring [Member] | Common stock and American Depositary Receipts (ADRs) [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 34.7 | 36.5 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 34.4 | 23.9 |
Fair Value, Measurements, Recurring [Member] | Exchangeable foreign ordinary equities and ADRs [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 10.4 | 25.7 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 10.5 | 25.8 |
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 29.1 | 40.8 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.3 | 6.9 |
Fair Value, Measurements, Recurring [Member] | US Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 60.0 | 514.9 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 285.9 | 509.8 |
Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 10.2 | 14.6 |
Financial Instruments Sold, Not yet Purchased, at Fair Value |  | 0.0 |
Fair Value, Measurements, Recurring [Member] | Mortgage Backed Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 920.9 | 747.5 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.1 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Derivative [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 162.1 | 193.9 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 317.0 | 210.9 |
Fair Value, Measurements, Recurring [Member] | Commodities leases and unpriced positions [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 35.4 | 8.1 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 41.5 | 62.1 |
Fair Value, Measurements, Recurring [Member] | Commodities warehouse receipts [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 38.5 | 8.9 |
Fair Value, Measurements, Recurring [Member] | Exchange firm common stock [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 8.3 |  |
Fair Value, Measurements, Recurring [Member] | Mutual funds and other [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 6.0 | 8.8 |
Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Brokers-Dealers and Clearing Organizations | 6.4 |  |
Fair Value, Measurements, Recurring [Member] | US Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Brokers-Dealers and Clearing Organizations | 244.7 |  |
Fair Value, Measurements, Recurring [Member] | TBA and forward settling securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Brokers-Dealers and Clearing Organizations | 8.8 |  |
Fair Value, Measurements, Recurring [Member] | Derivative [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Payables to Broker-Dealers and Clearing Organizations | (55.2) |  |
Fair Value, Measurements, Recurring [Member] | Mortgage Backed Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Exchange Clearing Organizations |  | 0.3 |
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Exchange Clearing Organizations |  | 512.7 |
Fair Value, Measurements, Recurring [Member] | US Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Exchange Clearing Organizations |  | 472.1 |
Fair Value, Measurements, Recurring [Member] | Derivative [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Payables to Broker-Dealers and Clearing Organizations |  | (131.8) |
Fair Value, Measurements, Recurring [Member] | Commodities warehouse receipts [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Cash and Securities Segregated under Federal and Other Regulations | 21.0 | 23.3 |
Fair Value, Measurements, Recurring [Member] | US Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Cash and Securities Segregated under Federal and Other Regulations | 33.5 | 595.5 |
Fair Value, Measurements, Recurring [Member] | Certificates of Deposit [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Cash and Cash Equivalents, Fair Value Disclosure | 3.8 |  | $ 3.8
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Cash and Cash Equivalents, Fair Value Disclosure |  | 7.1 |
Cash and Securities Segregated under Federal and Other Regulations | 54.5 | 23.3 |
Receivables from Exchange Clearing Organizations |  | 2,662.6 |
Receivables from Brokers-Dealers and Clearing Organizations | 2,853.3 |  |
Financial instruments owned, at fair value | 182.7 | 327.7 |
Assets, Fair Value Disclosure | 3,167.5 | 3,091.9 |
Payables to Broker-Dealers and Clearing Organizations | (2,476.2) |  |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 330.2 | 255.1 |
Liabilities, Fair Value Disclosure | 2,806.4 | 2,216.8 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | TBA and forward settling securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Payables to Broker-Dealers and Clearing Organizations | 0.0 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Derivative [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Payables to Broker-Dealers and Clearing Organizations | (2,476.2) | (1,961.7) |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Contingent Consideration [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Accounts payable and other accrued liabilities | 0.0 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Physical commodities inventory[Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Physical Commodities Inventory | 73.2 | 71.2 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Asset-backed Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 |  |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Government Agencies Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 |  |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.0 |  |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Common stock and American Depositary Receipts (ADRs) [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 31.2 | 34.6 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 33.7 | 23.5 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Exchangeable foreign ordinary equities and ADRs [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 9.2 | 25.2 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 10.3 | 25.3 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 28.2 | 36.9 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.3 | 6.9 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 60.0 | 0.0 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 285.9 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Foreign Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 | 0.0 |
Financial Instruments Sold, Not yet Purchased, at Fair Value |  | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Mortgage Backed Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 | 0.0 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.0 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Derivative [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 1.3 | 206.9 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.0 | 199.4 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Commodities leases and unpriced positions [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 | 0.0 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.0 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Commodities warehouse receipts [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 38.5 | 8.9 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Exchange firm common stock [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 8.3 | 6.4 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Mutual funds and other [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 6.0 | 8.8 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Foreign Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Brokers-Dealers and Clearing Organizations | 0.0 |  |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Brokers-Dealers and Clearing Organizations | 244.7 |  |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | TBA and forward settling securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Brokers-Dealers and Clearing Organizations | 0.0 |  |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Derivative [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Brokers-Dealers and Clearing Organizations | 2,608.6 |  |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Mortgage Backed Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Exchange Clearing Organizations |  | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Exchange Clearing Organizations |  | 512.7 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Exchange Clearing Organizations |  | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Derivative [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Exchange Clearing Organizations |  | 2,149.9 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Commodities warehouse receipts [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Cash and Securities Segregated under Federal and Other Regulations | 21.0 | 23.3 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Cash and Securities Segregated under Federal and Other Regulations | 33.5 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Certificates of Deposit [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Cash and Cash Equivalents, Fair Value Disclosure | 3.8 |  | 3.8
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Cash and Cash Equivalents, Fair Value Disclosure |  | 0.0 |
Cash and Securities Segregated under Federal and Other Regulations | 0.0 | 595.5 |
Receivables from Exchange Clearing Organizations |  | 480.4 |
Receivables from Brokers-Dealers and Clearing Organizations | 304.3 |  |
Financial instruments owned, at fair value | 2,940.3 | 2,768.1 |
Assets, Fair Value Disclosure | 3,244.6 | 3,844.0 |
Payables to Broker-Dealers and Clearing Organizations | (297.7) |  |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 1,647.2 | 2,037.8 |
Liabilities, Fair Value Disclosure | 1,944.9 | 2,137.9 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | TBA and forward settling securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Payables to Broker-Dealers and Clearing Organizations | (4.9) | (2.6) |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Derivative [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Payables to Broker-Dealers and Clearing Organizations | (292.8) | (97.5) |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Contingent Consideration [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Accounts payable and other accrued liabilities | 0.0 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Physical commodities inventory[Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Physical Commodities Inventory | 0.0 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Asset-backed Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 47.3 |  |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Government Agencies Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 368.9 |  |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 27.9 |  |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Common stock and American Depositary Receipts (ADRs) [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 3.4 | 1.7 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.7 | 0.4 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Exchangeable foreign ordinary equities and ADRs [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 1.2 | 0.5 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.2 | 0.5 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.9 | 0.9 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.0 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 | 514.9 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.0 | 509.8 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Foreign Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 10.2 | 14.6 |
Financial Instruments Sold, Not yet Purchased, at Fair Value |  | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Mortgage Backed Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 920.9 | 747.5 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.1 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Derivative [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 1,413.4 | 1,350.8 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 1,427.2 | 1,319.3 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Commodities leases and unpriced positions [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 174.1 | 137.2 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 191.1 | 207.8 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Commodities warehouse receipts [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Exchange firm common stock [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Mutual funds and other [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Foreign Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Brokers-Dealers and Clearing Organizations | 6.4 |  |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Brokers-Dealers and Clearing Organizations | 0.0 |  |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | TBA and forward settling securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Brokers-Dealers and Clearing Organizations | 8.8 |  |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Derivative [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Brokers-Dealers and Clearing Organizations | 289.1 |  |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Mortgage Backed Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Exchange Clearing Organizations |  | 0.3 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Exchange Clearing Organizations |  | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Exchange Clearing Organizations |  | 472.1 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Derivative [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Exchange Clearing Organizations |  | 8.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Commodities warehouse receipts [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Cash and Securities Segregated under Federal and Other Regulations | 0.0 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Cash and Securities Segregated under Federal and Other Regulations | 0.0 | 595.5 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Certificates of Deposit [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Cash and Cash Equivalents, Fair Value Disclosure | 0.0 |  | 0.0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Cash and Cash Equivalents, Fair Value Disclosure |  | 0.0 |
Cash and Securities Segregated under Federal and Other Regulations | 0.0 | 0.0 |
Receivables from Exchange Clearing Organizations |  | 0.0 |
Receivables from Brokers-Dealers and Clearing Organizations | 0.0 |  |
Financial instruments owned, at fair value | 0.1 | 3.2 |
Assets, Fair Value Disclosure | 0.1 | 3.2 |
Payables to Broker-Dealers and Clearing Organizations | 0.0 |  |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.0 | 0.0 |
Liabilities, Fair Value Disclosure | 1.0 | 0.8 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | TBA and forward settling securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Payables to Broker-Dealers and Clearing Organizations | 0.0 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Payables to Broker-Dealers and Clearing Organizations | 0.0 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Contingent Consideration [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Accounts payable and other accrued liabilities | 1.0 | 0.8 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Physical commodities inventory[Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Physical Commodities Inventory | 0.0 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Asset-backed Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 |  |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Government Agencies Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 |  |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.0 |  |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Common stock and American Depositary Receipts (ADRs) [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.1 | 0.2 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.0 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Exchangeable foreign ordinary equities and ADRs [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 | 0.0 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.0 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 | 3.0 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.0 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 | 0.0 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.0 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Foreign Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 | 0.0 |
Financial Instruments Sold, Not yet Purchased, at Fair Value |  | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Mortgage Backed Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 | 0.0 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.0 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 | 0.0 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.0 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Commodities leases and unpriced positions [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 | 0.0 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.0 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Commodities warehouse receipts [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Exchange firm common stock [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Mutual funds and other [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Foreign Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Brokers-Dealers and Clearing Organizations | 0.0 |  |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Brokers-Dealers and Clearing Organizations | 0.0 |  |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | TBA and forward settling securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Brokers-Dealers and Clearing Organizations | 0.0 |  |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Brokers-Dealers and Clearing Organizations | 0.0 |  |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Mortgage Backed Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Exchange Clearing Organizations |  | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Exchange Clearing Organizations |  | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Exchange Clearing Organizations |  | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Exchange Clearing Organizations |  | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Commodities warehouse receipts [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Cash and Securities Segregated under Federal and Other Regulations | 0.0 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Cash and Securities Segregated under Federal and Other Regulations | 0.0 | 0.0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Certificates of Deposit [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Cash and Cash Equivalents, Fair Value Disclosure | 0.0 |  | 0.0
Derivative [Member] | Fair Value, Measurements, Recurring [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Payables to Broker-Dealers and Clearing Organizations |  | (3.5) |
Derivative [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Payables to Broker-Dealers and Clearing Organizations |  | (1,961.7) |
Derivative [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Payables to Broker-Dealers and Clearing Organizations |  | (100.1) |
Derivative [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Payables to Broker-Dealers and Clearing Organizations |  | 0.0 |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Cash and Cash Equivalents, Fair Value Disclosure |  | 0.0 |
Cash and Securities Segregated under Federal and Other Regulations | 0.0 | 0.0 |
Receivables from Exchange Clearing Organizations |  | (2,289.7) |
Receivables from Brokers-Dealers and Clearing Organizations | (2,952.9) |  |
Financial instruments owned, at fair value | (1,391.3) | (1,492.9) |
Assets, Fair Value Disclosure | (4,344.2) | (3,782.6) |
Payables to Broker-Dealers and Clearing Organizations | 2,769.1 |  |
Financial Instruments Sold, Not yet Purchased, at Fair Value | (1,259.8) | (1,453.5) |
Liabilities, Fair Value Disclosure | (4,028.9) | (3,511.8) |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | TBA and forward settling securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Payables to Broker-Dealers and Clearing Organizations | 0.1 | (0.9) |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Derivative [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Payables to Broker-Dealers and Clearing Organizations | 2,769.0 | 2,059.2 |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Contingent Consideration [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Accounts payable and other accrued liabilities | 0.0 | 0.0 |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Physical commodities inventory[Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Physical Commodities Inventory | 0.0 | 0.0 |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Asset-backed Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 |  |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 |  |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.0 |  |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Common stock and American Depositary Receipts (ADRs) [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 | 0.0 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.0 | 0.0 |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Exchangeable foreign ordinary equities and ADRs [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 | 0.0 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.0 | 0.0 |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 | 0.0 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.0 | 0.0 |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | US Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 | 0.0 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.0 | 0.0 |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 | 0.0 |
Financial Instruments Sold, Not yet Purchased, at Fair Value |  | 0.0 |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Mortgage Backed Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 | 0.0 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.0 | 0.0 |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Derivative [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | (1,252.6) | (1,363.8) |
Financial Instruments Sold, Not yet Purchased, at Fair Value | (1,110.2) | (1,307.8) |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Commodities leases and unpriced positions [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | (138.7) | (129.1) |
Financial Instruments Sold, Not yet Purchased, at Fair Value | (149.6) | (145.7) |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Commodities warehouse receipts [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 | 0.0 |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Exchange firm common stock [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 | 0.0 |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Mutual funds and other [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Financial instruments owned, at fair value | 0.0 | 0.0 |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Brokers-Dealers and Clearing Organizations | 0.0 |  |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | US Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Brokers-Dealers and Clearing Organizations | 0.0 |  |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | TBA and forward settling securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Brokers-Dealers and Clearing Organizations | 0.0 |  |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Derivative [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Brokers-Dealers and Clearing Organizations | (2,952.9) |  |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Mortgage Backed Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Exchange Clearing Organizations |  | 0.0 |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Exchange Clearing Organizations |  | 0.0 |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | US Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Exchange Clearing Organizations |  | 0.0 |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Derivative [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Receivables from Exchange Clearing Organizations |  | (2,289.7) |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Commodities warehouse receipts [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Cash and Securities Segregated under Federal and Other Regulations | 0.0 | 0.0 |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | US Government Debt Securities [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Cash and Securities Segregated under Federal and Other Regulations | 0.0 | 0.0 |
Counterparty And Cash Collateral Netting Adjustment [Member] | Fair Value, Measurements, Recurring [Member] | Certificates of Deposit [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Cash and Cash Equivalents, Fair Value Disclosure | $ 0.0 |  | $ 0.0
Counterparty And Cash Collateral Netting Adjustment [Member] | Derivative [Member] | Fair Value, Measurements, Recurring [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Payables to Broker-Dealers and Clearing Organizations |  | $ 2,058.3 |

X
- Definition Amount of liabilities incurred and payable to vendors for goods and services received, and accrued liabilities classified as other. + References No definition available. + Details
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- Definition Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
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- Definition Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. + References No definition available. + Details
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- Definition Amount of cash subject to withdrawal restrictions, restricted deposits held as compensating balances, and cash and securities segregated in compliance with regulations (such as cash deposited in a special reserve account for the exclusive benefit of customers). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 305 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6478312&loc=d3e61473-112792 + Details
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