v2.4.0.6
Derivative Instruments (Consolidated Balance Sheets And Fair Value Of The Principal Derivative Instruments) (Details) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2013
Dec. 31, 2012
Derivative Assets    
Gross Amounts of Recognized Assets $ 85,752 $ 54,382
Gross Amounts Offset in the Balance Sheet 32,073 16,001
Net Amounts of Assets Presented in the Balance Sheet 53,679 38,381
Collateral 248 3,596
Net Amount 53,431 34,785
Derivative Liabilities    
Gross Amounts of Recognized Liabilities 50,162 38,471
Derivative Liability, Collateral, Right to Reclaim Cash, Offset 20,146 19,213
Net Amounts of Liabilities Presented in the Balance Sheet 30,016 19,258
Collateral 1,546 41
Net Amount 28,470 19,217
Other Assets [Member] | Interest Rate Futures [Member]
    
Derivative Assets    
Gross Amounts of Recognized Assets 429 441
Gross Amounts Offset in the Balance Sheet 0 0
Net Amounts of Assets Presented in the Balance Sheet 429 441
Collateral 0 0
Net Amount 429 441
Other Assets [Member] | Foreign Currency Forward Contracts, Underwriting and Non-investment Operations [Member]
    
Derivative Assets    
Gross Amounts of Recognized Assets 8,070 [1] 7,191 [1]
Gross Amounts Offset in the Balance Sheet 0 [1] 0 [1]
Net Amounts of Assets Presented in the Balance Sheet 8,070 [1] 7,191 [1]
Collateral 0 [1] 0 [1]
Net Amount 8,070 [1] 7,191 [1]
Other Assets [Member] | Foreign Currency Forward Contracts, Investment Operations [Member]
    
Derivative Assets    
Gross Amounts of Recognized Assets 6,541 [2] 2,534 [2]
Gross Amounts Offset in the Balance Sheet 5,880 [2] 2,296 [2]
Net Amounts of Assets Presented in the Balance Sheet 661 [2] 238 [2]
Collateral 0 [2] 0 [2]
Net Amount 661 [2] 238 [2]
Other Assets [Member] | Credit Default Swap [Member]
    
Derivative Assets    
Gross Amounts of Recognized Assets 547 784
Gross Amounts Offset in the Balance Sheet 299 333
Net Amounts of Assets Presented in the Balance Sheet 248 451
Collateral 248 310
Net Amount 0 141
Other Assets [Member] | Energy And Weather Contracts [Member]
    
Derivative Assets    
Gross Amounts of Recognized Assets 70,165 43,432
Gross Amounts Offset in the Balance Sheet 25,894 13,372
Net Amounts of Assets Presented in the Balance Sheet 44,271 30,060
Collateral 0 3,286
Net Amount 44,271 26,774
Other Liabilities [Member] | Interest Rate Futures [Member]
    
Derivative Liabilities    
Gross Amounts of Recognized Liabilities 30 41
Derivative Liability, Collateral, Right to Reclaim Cash, Offset 0 0
Net Amounts of Liabilities Presented in the Balance Sheet 30 41
Collateral 30 41
Net Amount 0 0
Other Liabilities [Member] | Foreign Currency Forward Contracts, Underwriting and Non-investment Operations [Member]
    
Derivative Liabilities    
Gross Amounts of Recognized Liabilities 4,227 [1] 4,173 [1]
Derivative Liability, Collateral, Right to Reclaim Cash, Offset 0 [1] 0 [1]
Net Amounts of Liabilities Presented in the Balance Sheet 4,227 [1] 4,173 [1]
Collateral 0 [1] 0 [1]
Net Amount 4,227 [1] 4,173 [1]
Other Liabilities [Member] | Foreign Currency Forward Contracts, Energy And Risk Operations [Member]
    
Derivative Liabilities    
Gross Amounts of Recognized Liabilities 211 [3] 579 [3]
Derivative Liability, Collateral, Right to Reclaim Cash, Offset 58 [3] 53 [3]
Net Amounts of Liabilities Presented in the Balance Sheet 153 [3] 526 [3]
Collateral 153 [3] 0 [3]
Net Amount 0 [3] 526 [3]
Other Liabilities [Member] | Energy And Weather Contracts [Member]
    
Derivative Liabilities    
Gross Amounts of Recognized Liabilities 45,694 33,678
Derivative Liability, Collateral, Right to Reclaim Cash, Offset 20,088 19,160
Net Amounts of Liabilities Presented in the Balance Sheet 25,606 14,518
Collateral 1,363 0
Net Amount $ 24,243 $ 14,518
[1] Contracts used to manage foreign currency risks in underwriting and non-investment operations.
[2] Contracts used to manage foreign currency risks in investment operations.
[3] Contracts used to manage foreign currency risks in energy and risk operations.