Assets and Liabilities, at Fair Value - Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Millions | Jun. 30, 2015 | Sep. 30, 2014 |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash and Securities Segregated under Federal and Other Regulations | $ 865 | $ 448 |
Receivables from Clearing Organizations | 1,153.3 | 1,731.4 |
Receivables from Brokers-Dealers and Clearing Organizations | 144.3 | 123 |
Financial Instruments, Owned, at Fair Value | 1,310 | 197.9 |
Physical commodities inventory | 46.1 | 40 |
Assets, Fair Value Disclosure | 2,824.3 | 1,469 |
Accounts Payable and Other Accrued Liabilities | 115.7 | 114.1 |
Payables to Broker-Dealers and Clearing Organizations | 61.8 | 11.9 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 523.1 | 264 |
Fair Value, Measurements, Recurring [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash and Securities Segregated under Federal and Other Regulations | 511.8 | 15.3 |
Receivables from Clearing Organizations | 1,002.8 | 1,255.4 |
Receivables from Brokers-Dealers and Clearing Organizations | (16.2) | |
Financial Instruments, Owned, at Fair Value | 1,310 | 197.9 |
Assets, Fair Value Disclosure | 2,824.3 | 1,469 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 523.1 | |
Liabilities, Fair Value Disclosure | 526.4 | 269.5 |
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 |
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 | 3.3 | 5.5 |
Fair Value, Measurements, Recurring [Member] | Physical commodities inventory - precious metals [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Physical commodities inventory | 14 | |
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 | 24.1 | 82.5 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 24.5 | 95.4 |
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 | 72.3 | 27.2 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 69.4 | 5.8 |
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 | 22.4 | 19.7 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 321.7 | 2.8 |
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 | 479.6 | 0.3 |
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 | 10.5 | 10.7 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.3 | |
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 | 40.1 | 44.3 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 52.6 | 84.4 |
Fair Value, Measurements, Recurring [Member] | Commodities leases [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Financial Instruments, Owned, at Fair Value | 1.2 | 2.1 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 54.4 | 75.6 |
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 | | 3.6 |
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 | 5.6 | 4.8 |
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 | 1.9 | 2.7 |
Fair Value, Measurements, Recurring [Member] | Collateralized Mortgage Backed Securities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Financial Instruments, Owned, at Fair Value | 652.3 | |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.2 | |
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 | 1.3 | |
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 | (17.5) | (1.1) |
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Receivables from Clearing Organizations | 289.7 | 826.8 |
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 Clearing Organizations | 478.2 | 702.5 |
Fair Value, Measurements, Recurring [Member] | Derivative [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Receivables from Clearing Organizations | 234.9 | (273.9) |
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 | 18.9 | 14.8 |
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 | 492.9 | 0.5 |
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 | 1.9 | 1.5 |
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 Securities Segregated under Federal and Other Regulations | 18.9 | 14.8 |
Receivables from Clearing Organizations | 3,352.9 | 4,223.9 |
Receivables from Brokers-Dealers and Clearing Organizations | 304.6 | |
Financial Instruments, Owned, at Fair Value | 478 | 444.6 |
Assets, Fair Value Disclosure | 4,170.3 | 5,233.8 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 442.7 | 428.4 |
Liabilities, Fair Value Disclosure | 4,054.6 | 3,898.2 |
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 | 3,611.9 | 3,469.8 |
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 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Physical commodities inventory - precious metals [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Physical commodities inventory | 14 | |
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 | 22.1 | 66.8 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 24.1 | 92.8 |
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 | 67.3 | 27.2 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 60.9 | 5.8 |
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 | 16 | 7.1 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0 | 2.8 |
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 | 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 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 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 | 365.1 | 332.4 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 357.7 | 327 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Commodities leases [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] | Commodities warehouse receipts [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Financial Instruments, Owned, at Fair Value | | 3.6 |
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 | 5.6 | 4.8 |
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 | 1.9 | 2.7 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Collateralized Mortgage Backed Securities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Financial Instruments, Owned, at Fair Value | 0 | |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 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] | | |
Receivables from Brokers-Dealers and Clearing Organizations | 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 | 304.6 | 549 |
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 Clearing Organizations | 289.7 | 826.8 |
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 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 Clearing Organizations | 3,063.2 | 3,397.1 |
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 | 18.9 | 14.8 |
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 | 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 | 1.9 | 1.5 |
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 Securities Segregated under Federal and Other Regulations | 492.9 | 0.5 |
Receivables from Clearing Organizations | 478.2 | 702.5 |
Receivables from Brokers-Dealers and Clearing Organizations | 2.8 | |
Financial Instruments, Owned, at Fair Value | 2,349.1 | 2,423.4 |
Assets, Fair Value Disclosure | 3,323 | 3,126.4 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 1,652.2 | 2,436.3 |
Liabilities, Fair Value Disclosure | 1,653.6 | 2,436.3 |
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 | 1.4 | 0 |
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 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Physical commodities inventory - precious metals [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Physical commodities inventory | 0 | |
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 | 1.5 | 15 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.4 | 2.6 |
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 | 5 | 0 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 8.5 | 0 |
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 | 2.9 | 9 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 321.7 | 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 | 479.6 | 0.3 |
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 | 10.5 | 10.7 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.3 | |
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 | 1,103.4 | 2,328.3 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 1,192.9 | 2,257.7 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Commodities leases [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Financial Instruments, Owned, at Fair Value | 93.9 | 60.1 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 128.2 | 176 |
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 |
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 |
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 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Collateralized Mortgage Backed Securities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Financial Instruments, Owned, at Fair Value | 652.3 | |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0.2 | |
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 | 1.3 | |
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 | 1.5 | 0 |
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 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 Clearing Organizations | 478.2 | 702.5 |
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 Clearing Organizations | 0 | 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 |
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 | 492.9 | 0.5 |
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 |
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 Securities Segregated under Federal and Other Regulations | 0 | 0 |
Receivables from Clearing Organizations | 0 | 0 |
Receivables from Brokers-Dealers and Clearing Organizations | 0 | |
Financial Instruments, Owned, at Fair Value | 4 | 4.3 |
Assets, Fair Value Disclosure | 4 | 4.3 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0 | 0 |
Liabilities, Fair Value Disclosure | 3.3 | 5.5 |
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 |
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 | 3.3 | 5.5 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Physical commodities inventory - precious metals [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Physical commodities inventory | 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 | 0.5 | 0.7 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 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 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 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 | 3.5 | 3.6 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 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 |
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 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 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 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Commodities leases [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] | Commodities warehouse receipts [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Financial Instruments, Owned, at Fair Value | | 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 |
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 |
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Collateralized Mortgage Backed Securities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Financial Instruments, Owned, at Fair Value | 0 | |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 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 | |
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] | Money Market Funds [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Receivables from 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 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 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 |
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 |
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 |
Fair Value, Measurements, Recurring [Member] | Cash collateral and counterparty netting [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 |
Receivables from Clearing Organizations | (2,828.3) | (3,671) |
Receivables from Brokers-Dealers and Clearing Organizations | (323.6) | |
Financial Instruments, Owned, at Fair Value | (1,521.1) | (2,674.4) |
Assets, Fair Value Disclosure | (4,673) | (6,895.5) |
Financial Instruments Sold, Not yet Purchased, at Fair Value | (1,571.8) | (2,600.7) |
Liabilities, Fair Value Disclosure | (5,185.1) | (6,070.5) |
Fair Value, Measurements, Recurring [Member] | Cash collateral and counterparty netting [Member] | Derivative [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Payables to Broker-Dealers and Clearing Organizations | (3,613.3) | (3,469.8) |
Fair Value, Measurements, Recurring [Member] | Cash collateral and counterparty netting [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 |
Fair Value, Measurements, Recurring [Member] | Cash collateral and counterparty netting [Member] | Physical commodities inventory - precious metals [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Physical commodities inventory | 0 | |
Fair Value, Measurements, Recurring [Member] | Cash collateral and counterparty netting [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 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Cash collateral and counterparty netting [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 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Cash collateral and counterparty netting [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 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Cash collateral and counterparty netting [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 |
Fair Value, Measurements, Recurring [Member] | Cash collateral and counterparty netting [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 |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0 | |
Fair Value, Measurements, Recurring [Member] | Cash collateral and counterparty netting [Member] | Derivative [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Financial Instruments, Owned, at Fair Value | (1,428.4) | (2,616.4) |
Financial Instruments Sold, Not yet Purchased, at Fair Value | (1,498) | (2,500.3) |
Fair Value, Measurements, Recurring [Member] | Cash collateral and counterparty netting [Member] | Commodities leases [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Financial Instruments, Owned, at Fair Value | (92.7) | (58) |
Financial Instruments Sold, Not yet Purchased, at Fair Value | (73.8) | (100.4) |
Fair Value, Measurements, Recurring [Member] | Cash collateral and counterparty netting [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 |
Fair Value, Measurements, Recurring [Member] | Cash collateral and counterparty netting [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 |
Fair Value, Measurements, Recurring [Member] | Cash collateral and counterparty netting [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 |
Fair Value, Measurements, Recurring [Member] | Cash collateral and counterparty netting [Member] | Collateralized Mortgage Backed Securities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Financial Instruments, Owned, at Fair Value | 0 | |
Financial Instruments Sold, Not yet Purchased, at Fair Value | 0 | |
Fair Value, Measurements, Recurring [Member] | Cash collateral and counterparty netting [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 | |
Fair Value, Measurements, Recurring [Member] | Cash collateral and counterparty netting [Member] | Derivative [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Receivables from Brokers-Dealers and Clearing Organizations | (323.6) | (550.1) |
Fair Value, Measurements, Recurring [Member] | Cash collateral and counterparty netting [Member] | Money Market Funds [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Receivables from Clearing Organizations | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Cash collateral and counterparty netting [Member] | US Government Debt Securities [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Receivables from Clearing Organizations | 0 | 0 |
Fair Value, Measurements, Recurring [Member] | Cash collateral and counterparty netting [Member] | Derivative [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Receivables from Clearing Organizations | (2,828.3) | (3,671) |
Fair Value, Measurements, Recurring [Member] | Cash collateral and counterparty netting [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 |
Fair Value, Measurements, Recurring [Member] | Cash collateral and counterparty netting [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 |
Fair Value, Measurements, Recurring [Member] | Cash collateral and counterparty netting [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 |