v2.4.0.6
Derivative Instruments (Consolidated Balance Sheets And Fair Value Of The Principal Derivative Instruments) (Details) (USD $)
Jun. 30, 2012
Dec. 31, 2011
Derivative Assets [Abstract]    
Derivative Asset, Net $ 37,945,000 $ 60,939,000
Derivative Liabilities [Abstract]    
Derivative Liabilities, Net 23,193,000 57,627,000
Other Assets [Member] | Interest Rate Futures [Member]
    
Derivative Assets [Abstract]    
Derivative Asset, Net 2,301,000 612,000
Other Assets [Member] | Foreign Currency Forward Contracts, Underwriting and Non-investment Operations [Member]
    
Derivative Assets [Abstract]    
Derivative Asset, Net 4,278,000 [1] 0 [1]
Other Assets [Member] | Foreign Currency Forward Contracts, Energy And Risk Operations [Member]
    
Derivative Assets [Abstract]    
Derivative Asset, Net 0 [2] 387,000 [2]
Derivative Liabilities [Abstract]    
Derivative Liabilities, Net 175,000 [2] 0 [2]
Other Assets [Member] | Credit Default Swap [Member]
    
Derivative Assets [Abstract]    
Derivative Asset, Net 491,000 0
Other Assets [Member] | Energy And Weather Contracts [Member]
    
Derivative Assets [Abstract]    
Derivative Asset, Net 27,516,000 [3] 52,721,000 [3]
Energy and Weather Contracts [Abstract]    
Derivative asset, gross asset component 56,800,000 104,600,000
Derivative asset, gross liability component 29,300,000 51,900,000
Other Liabilities [Member] | Interest Rate Futures [Member]
    
Derivative Liabilities [Abstract]    
Derivative Liabilities, Net 289,000 339,000
Other Liabilities [Member] | Foreign Currency Forward Contracts, Underwriting and Non-investment Operations [Member]
    
Derivative Liabilities [Abstract]    
Derivative Liabilities, Net 4,987,000 [1] 11,754,000 [1]
Other Liabilities [Member] | Foreign Currency Forward Contracts, Investment Operations [Member]
    
Derivative Assets [Abstract]    
Derivative Asset, Net 3,359,000 [4] 7,219,000 [4]
Derivative Liabilities [Abstract]    
Derivative Liabilities, Net 3,684,000 [4] 1,606,000 [4]
Other Liabilities [Member] | Credit Default Swap [Member]
    
Derivative Liabilities [Abstract]    
Derivative Liabilities, Net 536,000 539,000
Other Liabilities [Member] | Energy And Weather Contracts [Member]
    
Derivative Liabilities [Abstract]    
Derivative Liabilities, Net 13,522,000 [3] 43,389,000 [3]
Energy and Weather Contracts [Abstract]    
Derivative liability, gross asset component 5,200,000 8,800,000
Derivative liability, gross liability component $ 18,700,000 $ 52,200,000
[1] Contracts used to manage foreign currency risks in underwriting and non-investment operations.
[2] Contracts used to manage foreign currency risks in energy and risk operations.
[3] Included in other assets is $56.8 million of derivative assets (December 31, 2011 – $104.6 million) and $29.3 million of derivative liabilities (December 31, 2011 – $51.9 million). Included in other liabilities is $5.2 million of derivative assets (December 31, 2011 – $8.8 million) and $18.7 million of derivative liabilities (December 31, 2011 – $52.2 million).
[4] Contracts used to manage foreign currency risks in investment operations. Included in other liabilities are derivative assets of $3.4 million (December 31, 2011 – $7.2 million) which are netted with derivative liabilities of $3.7 million (December 31, 2011 – $1.6 million) under a master netting arrangements.