v2.4.0.6
Fair Value Measurements (Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Level 3 Inputs) (Details) (USD $)
In Thousands, unless otherwise specified
3 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Other investments $ 652,802   $ 644,711
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Balance at beginning of the period 434,799 452,813  
Total unrealized gains (losses)      
Included in net investment income 13,291 29,184  
Included in other income (loss) 9,776 18,563  
Total realized gains (losses)      
Included in other income (loss) 6,108 (55,308)  
Total foreign exchange gains (losses) (861) 353  
Purchases 10,785 21,970  
Sales (424) (13,431)  
Settlements (21,873) 40,376  
Reclassified from other assets to other investments 0    
Net transfers into Level 3 0 0  
Balance at end of the period 451,601 494,520  
Change in unrealized gains for the period included in earnings for assets held at the end of the period included in net investment income (loss) 13,291 29,184  
Change in unrealized losses for the period included in earnings for assets held at the end of the period included in other (loss) income 11,893 10,513  
Assets and (liabilities) at fair value 22,958   29,085
Fixed maturity investments [Member]
     
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Balance at beginning of the period 27,792 27,761  
Total unrealized gains (losses)      
Included in net investment income 275 77  
Included in other income (loss) 0 0  
Total realized gains (losses)      
Included in other income (loss) 0 0  
Total foreign exchange gains (losses) 0 0  
Purchases 0 0  
Sales 0 0  
Settlements 0 0  
Reclassified from other assets to other investments 0    
Net transfers into Level 3 0 0  
Balance at end of the period 28,067 27,838  
Change in unrealized gains for the period included in earnings for assets held at the end of the period included in net investment income (loss) 275 77  
Change in unrealized losses for the period included in earnings for assets held at the end of the period included in other (loss) income 0 0  
Other Investments [Member]
     
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Balance at beginning of the period 381,067 396,526  
Total unrealized gains (losses)      
Included in net investment income 13,016 29,107  
Included in other income (loss) 0 0  
Total realized gains (losses)      
Included in other income (loss) 0 0  
Total foreign exchange gains (losses) (781) 730  
Purchases 10,785 12,689  
Sales (424) 0  
Settlements (19,699) (20,515)  
Reclassified from other assets to other investments 18,242    
Net transfers into Level 3 0 0  
Balance at end of the period 402,206 418,537  
Change in unrealized gains for the period included in earnings for assets held at the end of the period included in net investment income (loss) 13,016 29,107  
Change in unrealized losses for the period included in earnings for assets held at the end of the period included in other (loss) income 0 0  
Other Assets and (Liabilities) [Member]
     
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Balance at beginning of the period 25,940 28,526  
Total unrealized gains (losses)      
Included in net investment income 0 0  
Included in other income (loss) 9,776 18,563  
Total realized gains (losses)      
Included in other income (loss) 6,108 (55,308)  
Total foreign exchange gains (losses) (80) (377)  
Purchases 0 9,281  
Sales 0 (13,431)  
Settlements (2,174) 60,891  
Reclassified from other assets to other investments (18,242)    
Net transfers into Level 3 0 0  
Balance at end of the period 21,328 48,145  
Change in unrealized gains for the period included in earnings for assets held at the end of the period included in net investment income (loss) 0 0  
Change in unrealized losses for the period included in earnings for assets held at the end of the period included in other (loss) income 11,893 10,513  
Fair Value, Inputs, Level 3 [Member]
     
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Assets, Fair Value Disclosure, Recurring 451,601    
Other investments 402,206   381,067
Total realized gains (losses)      
Assets (Liabilities), Fair Value Disclosure, Recurring 21,328    
Assets and (liabilities) at fair value 21,328   25,940
Fair Value, Inputs, Level 3 [Member] | Fixed maturity investments [Member]
     
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Assets, Fair Value Disclosure, Recurring 28,067    
Fair Value, Inputs, Level 3 [Member] | Other Investments [Member]
     
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Assets, Fair Value Disclosure, Recurring 402,206    
Fair Value, Inputs, Level 3 [Member] | Discounted Cash Flow Valuation Technique [Member] | Corporate [Member]
     
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Assets, Fair Value Disclosure, Recurring 17,813    
Fair Value, Inputs, Level 3 [Member] | Internal Valuation Model Valuation Technique [Member] | Corporate [Member]
     
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Assets, Fair Value Disclosure, Recurring 10,254    
Fair Value, Inputs, Level 3 [Member] | Internal Valuation Model Valuation Technique [Member] | Assumed And Ceded Re Insurance Contracts Member
     
Total realized gains (losses)      
Assets (Liabilities), Fair Value Disclosure, Recurring 676    
Assets and (liabilities) at fair value 676    
Fair Value, Inputs, Level 3 [Member] | Internal Valuation Model Valuation Technique [Member] | Other [Member]
     
Total realized gains (losses)      
Assets (Liabilities), Fair Value Disclosure, Recurring 625    
Fair Value, Inputs, Level 3 [Member] | Net Asset Valuation Technique [Member] | Private Equity Funds [Member]
     
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Assets, Fair Value Disclosure, Recurring 345,666    
Other investments 345,666    
Fair Value, Inputs, Level 3 [Member] | Net Asset Valuation Technique [Member] | Senior secured bank loan funds [Member]
     
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Assets, Fair Value Disclosure, Recurring 28,537    
Other investments 28,537    
Fair Value, Inputs, Level 3 [Member] | Net Asset Valuation Technique [Member] | Hedge funds [Member]
     
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Assets, Fair Value Disclosure, Recurring 5,219    
Other investments 5,219    
Fair Value, Inputs, Level 3 [Member] | Net Asset Valuation Technique [Member] | Other [Member]
     
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Assets, Fair Value Disclosure, Recurring 22,784    
Total realized gains (losses)      
Assets (Liabilities), Fair Value Disclosure, Recurring 22,784    
Weighted Average or Actual [Member] | Fair Value, Inputs, Level 3 [Member] | Discounted Cash Flow Valuation Technique [Member] | Corporate [Member]
     
Total realized gains (losses)      
Credit spread 2.40%    
Liquidity premium 1.00%    
Risk-free rate 0.10%    
Dividend rate 5.90%    
Weighted Average or Actual [Member] | Fair Value, Inputs, Level 3 [Member] | Net Asset Valuation Technique [Member] | Private Equity Funds [Member]
     
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Fair Value Inputs, Estimated Performance 4.90%    
Weighted Average or Actual [Member] | Fair Value, Inputs, Level 3 [Member] | Net Asset Valuation Technique [Member] | Senior secured bank loan funds [Member]
     
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Fair Value Inputs, Estimated Performance 1.30%    
Weighted Average or Actual [Member] | Fair Value, Inputs, Level 3 [Member] | Net Asset Valuation Technique [Member] | Hedge funds [Member]
     
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Fair Value Inputs, Estimated Performance 0.00%    
Weighted Average or Actual [Member] | Fair Value, Inputs, Level 3 [Member] | Net Asset Valuation Technique [Member] | Other [Member]
     
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Fair Value Inputs, Estimated Performance 0.90%    
Minimum [Member] | Fair Value, Inputs, Level 3 [Member] | Net Asset Valuation Technique [Member] | Private Equity Funds [Member]
     
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Fair Value Inputs, Estimated Performance (12.00%)    
Minimum [Member] | Fair Value, Inputs, Level 3 [Member] | Net Asset Valuation Technique [Member] | Senior secured bank loan funds [Member]
     
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Fair Value Inputs, Estimated Performance 0.80%    
Minimum [Member] | Fair Value, Inputs, Level 3 [Member] | Net Asset Valuation Technique [Member] | Hedge funds [Member]
     
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Fair Value Inputs, Estimated Performance 0.00%    
Maximum [Member] | Fair Value, Inputs, Level 3 [Member] | Net Asset Valuation Technique [Member] | Private Equity Funds [Member]
     
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Fair Value Inputs, Estimated Performance 120.00%    
Maximum [Member] | Fair Value, Inputs, Level 3 [Member] | Net Asset Valuation Technique [Member] | Senior secured bank loan funds [Member]
     
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Fair Value Inputs, Estimated Performance 2.10%    
Maximum [Member] | Fair Value, Inputs, Level 3 [Member] | Net Asset Valuation Technique [Member] | Hedge funds [Member]
     
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Fair Value Inputs, Estimated Performance 0.00%    
Derivatives Assets (Liabilities) Member
     
Total realized gains (losses)      
Assets and (liabilities) at fair value 23,663 [1]   19,123 [1]
Derivatives Assets (Liabilities) Member | Fair Value, Inputs, Level 3 [Member]
     
Total realized gains (losses)      
Assets and (liabilities) at fair value $ 20,027 [1]   $ 4,427 [1]
[1] See "Note 11. Derivative Instruments" for additional information related to the fair value by type of contract, of derivatives entered into by the Company.