v2.4.0.8
Financial Assets And Financial Liabilities (Fair Value Table) (Details) (USD $)
In Thousands, unless otherwise specified
Jun. 30, 2014
Dec. 31, 2013
Jun. 30, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Securities segregated for regulatory purposes $ 3,427,880 $ 1,300,016  
Financial instruments owned 2,398,625 3,285,313  
Financial instruments owned and pledged as collateral 839,467 1,163,531  
Total financial instruments owned 3,238,092 4,448,844  
Other fair value investments, included in other assets 34,961 130,750  
Total Financial Assets at Fair Value 6,700,933 5,879,610  
Financial instruments sold but not yet purchased, at fair value 2,630,785 3,153,673  
Other fair value liabilities, included in accounts payable, accrued expenses and other liabilities 132,036    
Total Financial Liabilities at Fair Value 2,762,821    
Common Stock [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial instruments owned 1,151,627 1,243,971  
Financial instruments owned and pledged as collateral 759,705 1,097,734  
Other fair value investments, included in other assets   26,124  
Financial instruments sold but not yet purchased, at fair value 1,370,907 1,266,432  
Stocks and options [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Other fair value investments, included in other assets 33,265    
Other fair value liabilities, included in accounts payable, accrued expenses and other liabilities 132,036    
Options [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial instruments owned 1,072,980 1,880,481  
Financial instruments sold but not yet purchased, at fair value 1,168,783 1,793,248  
Warrants And Discount Certificates [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial instruments owned 34,345 57,144  
Financial instruments sold but not yet purchased, at fair value 603 1,215  
Warrants [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial instruments owned and pledged as collateral 273 233  
U.S. And Foreign Government Securities [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial instruments owned 19,915 6,743  
Financial instruments owned and pledged as collateral 78,012 64,439  
Financial instruments sold but not yet purchased, at fair value 2,889 4,412  
Corporate And Municipal Bonds [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial instruments owned 111,163 91,226  
Financial instruments owned and pledged as collateral 1,477 1,125  
Other fair value investments, included in other assets 1,696 49,672  
Financial instruments sold but not yet purchased, at fair value 87,603 87,564  
Mortgage Backed Securities [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Other fair value investments, included in other assets   26,892  
Other Asset Backed Securities [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Other fair value investments, included in other assets   22,734  
Currency Forward Contracts [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial instruments owned 8,595 5,748  
Financial instruments sold but not yet purchased, at fair value   802  
Other Assets - Investments [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Other fair value investments, included in other assets   5,328  
Level 1
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Securities segregated for regulatory purposes 3,427,880 1,300,016  
Financial instruments owned 2,365,984 3,258,930  
Financial instruments owned and pledged as collateral 839,467 1,163,531  
Total financial instruments owned 3,205,451 4,422,461  
Other fair value investments, included in other assets 33,159 27,380  
Total Financial Assets at Fair Value 6,666,490 5,749,857  
Financial instruments sold but not yet purchased, at fair value 2,619,103 3,138,828  
Other fair value liabilities, included in accounts payable, accrued expenses and other liabilities 132,036    
Total Financial Liabilities at Fair Value 2,751,139    
Level 1 | Common Stock [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial instruments owned 1,151,367 1,243,914  
Financial instruments owned and pledged as collateral 759,705 1,097,734  
Other fair value investments, included in other assets   25,604  
Financial instruments sold but not yet purchased, at fair value 1,370,830 1,266,429  
Level 1 | Stocks and options [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Other fair value investments, included in other assets 33,159    
Other fair value liabilities, included in accounts payable, accrued expenses and other liabilities 132,036    
Level 1 | Options [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial instruments owned 1,072,980 1,880,481  
Financial instruments sold but not yet purchased, at fair value 1,168,783 1,793,248  
Level 1 | Warrants And Discount Certificates [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial instruments owned 34,345 57,144  
Financial instruments sold but not yet purchased, at fair value 603 1,215  
Level 1 | Warrants [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial instruments owned and pledged as collateral 273 233  
Level 1 | U.S. And Foreign Government Securities [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial instruments owned 16,049 4,641  
Financial instruments owned and pledged as collateral 78,012 64,439  
Financial instruments sold but not yet purchased, at fair value 1,840    
Level 1 | Corporate And Municipal Bonds [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial instruments owned 91,243 72,750  
Financial instruments owned and pledged as collateral 1,477 1,125  
Other fair value investments, included in other assets   1,776  
Financial instruments sold but not yet purchased, at fair value 77,047 77,936  
Level 2
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial instruments owned 32,381 26,326  
Total financial instruments owned 32,381 26,326  
Other fair value investments, included in other assets 1,696 103,269  
Total Financial Assets at Fair Value 34,077 129,595  
Financial instruments sold but not yet purchased, at fair value 11,605 14,842  
Total Financial Liabilities at Fair Value 11,605    
Level 2 | Common Stock [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Other fair value investments, included in other assets   419  
Level 2 | U.S. And Foreign Government Securities [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial instruments owned 3,866 2,102  
Financial instruments sold but not yet purchased, at fair value 1,049 4,412  
Level 2 | Corporate And Municipal Bonds [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial instruments owned 19,920 18,476  
Other fair value investments, included in other assets 1,696 47,896  
Financial instruments sold but not yet purchased, at fair value 10,556 9,628  
Level 2 | Mortgage Backed Securities [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Other fair value investments, included in other assets   26,892  
Level 2 | Other Asset Backed Securities [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Other fair value investments, included in other assets   22,734  
Level 2 | Currency Forward Contracts [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial instruments owned 8,595 5,748  
Financial instruments sold but not yet purchased, at fair value   802  
Level 2 | Other Assets - Investments [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Other fair value investments, included in other assets   5,328  
Level 3
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial instruments owned 260 57  
Total financial instruments owned 260 57  
Other fair value investments, included in other assets 106 101  
Total Financial Assets at Fair Value 366 158 0
Financial instruments sold but not yet purchased, at fair value 77 3 0
Total Financial Liabilities at Fair Value 77    
Level 3 | Common Stock [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Financial instruments owned 260 57  
Other fair value investments, included in other assets   101  
Financial instruments sold but not yet purchased, at fair value 77 3  
Level 3 | Stocks and options [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Other fair value investments, included in other assets $ 106