v2.4.0.8
Financial Assets And Financial Liabilities (Netting of Financial Liabilities) (Details) (USD $)
In Millions, unless otherwise specified
Jun. 30, 2014
Dec. 31, 2013
Offsetting Liabilities [Line Items]    
Gross Amounts of Recognized Liabilities $ 4,101.8 $ 4,358.9
Gross Amounts Liabilities Offset in the Consolidated Statement of Financial Condition 0 0
Net Amounts of Liabilities Presented in the Statement of Financial Condition 4,101.8 4,358.9
Gross Amounts of Liabilities Not Offset in the Consolidated Satement of Financial Position (Financial Instruments) (3,965.1) (4,198.6)
Gross Amounts Not Offset in the Consolidated Statement of Financial Position (Cash Collateral Pledged) 0 0
Net Amount of Liabilities 136.7 160.3
Securities Loaned [Member]
    
Offsetting Liabilities [Line Items]    
Gross Amounts of Recognized Liabilities 2,932.4 2,563.7
Gross Amounts Liabilities Offset in the Consolidated Statement of Financial Condition 0 0
Net Amounts of Liabilities Presented in the Statement of Financial Condition 2,932.4 2,563.7
Gross Amounts of Liabilities Not Offset in the Consolidated Satement of Financial Position (Financial Instruments) (2,932.0) (2,544.6)
Gross Amounts Not Offset in the Consolidated Statement of Financial Position (Cash Collateral Pledged) 0 0
Net Amount of Liabilities 0.4 19.1
Options Sold, Not Yet Purchased [Member]
    
Offsetting Liabilities [Line Items]    
Gross Amounts of Recognized Liabilities 1,168.8 1,793.2
Gross Amounts Liabilities Offset in the Consolidated Statement of Financial Condition 0 0
Net Amounts of Liabilities Presented in the Statement of Financial Condition 1,168.8 1,793.2
Gross Amounts of Liabilities Not Offset in the Consolidated Satement of Financial Position (Financial Instruments) (1,032.5) (1,652.8)
Gross Amounts Not Offset in the Consolidated Statement of Financial Position (Cash Collateral Pledged) 0 0
Net Amount of Liabilities 136.3 140.4
Warrants And Discount Certificates Sold, Not Yet Purchased [Member]
    
Offsetting Liabilities [Line Items]    
Gross Amounts of Recognized Liabilities 0.6 1.2
Gross Amounts Liabilities Offset in the Consolidated Statement of Financial Condition 0 0
Net Amounts of Liabilities Presented in the Statement of Financial Condition 0.6 1.2
Gross Amounts of Liabilities Not Offset in the Consolidated Satement of Financial Position (Financial Instruments) (0.6) (1.2)
Gross Amounts Not Offset in the Consolidated Statement of Financial Position (Cash Collateral Pledged) 0 0
Net Amount of Liabilities 0 0
Currency Forward Contracts Sold, Not Yet Purchased [Member]
    
Offsetting Liabilities [Line Items]    
Gross Amounts of Recognized Liabilities 0 0.8
Gross Amounts Liabilities Offset in the Consolidated Statement of Financial Condition 0 0
Net Amounts of Liabilities Presented in the Statement of Financial Condition 0 0.8
Gross Amounts of Liabilities Not Offset in the Consolidated Satement of Financial Position (Financial Instruments) 0 0
Gross Amounts Not Offset in the Consolidated Statement of Financial Position (Cash Collateral Pledged) 0 0
Net Amount of Liabilities $ 0 $ 0.8