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Fair Value Measurements Fair Value Measurements (Quantitative Information Used As Level 3 Inputs) (Details) (USD $)
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3 Months Ended | ||
|---|---|---|---|
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Mar. 31, 2012
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Mar. 31, 2011
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Dec. 31, 2011
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| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Net premiums written | $ 492,575,000 | $ 452,575,000 | |
| Net reserve for claims and claim expenses | 1,858,203,000 | 1,992,354,000 | |
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Senior secured bank loan funds [Member]
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| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Investment in closed end fund | 21,000,000 | ||
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Significant Unobservable Inputs (Level 3) [Member]
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|||
| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Assets, fair value | 494,520,000 | ||
| Other assets and (liabilities). fair value | 48,145,000 | ||
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Significant Unobservable Inputs (Level 3) [Member] | Corporate [Member] | Discounted Cash Flow Valuation Technique [Member]
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| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Assets, fair value | 17,584,000 | ||
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Significant Unobservable Inputs (Level 3) [Member] | Corporate [Member] | Discounted Cash Flow Valuation Technique [Member] | Weighted Average or Actual [Member]
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| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Credit spread | 4.10% | ||
| Illiquidity premium | 1.00% | ||
| Risk-free rate | 0.20% | ||
| Dividend rate | 5.90% | ||
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Significant Unobservable Inputs (Level 3) [Member] | Corporate [Member] | Internal Valuation Model Valuation Technique [Member]
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| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Assets, fair value | 10,254,000 | ||
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Significant Unobservable Inputs (Level 3) [Member] | Fixed Maturity Investments [Member]
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| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Assets, fair value | 27,838,000 | ||
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Significant Unobservable Inputs (Level 3) [Member] | Private Equity Funds [Member] | Net Asset Valuation Technique [Member]
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|||
| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Assets, fair value | 389,451,000 | ||
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Significant Unobservable Inputs (Level 3) [Member] | Private Equity Funds [Member] | Net Asset Valuation Technique [Member] | Minimum [Member]
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| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Estimated performance | (6.00%) | ||
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Significant Unobservable Inputs (Level 3) [Member] | Private Equity Funds [Member] | Net Asset Valuation Technique [Member] | Maximum [Member]
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| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Estimated performance | 64.40% | ||
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Significant Unobservable Inputs (Level 3) [Member] | Private Equity Funds [Member] | Net Asset Valuation Technique [Member] | Weighted Average or Actual [Member]
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| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Estimated performance | 8.40% | ||
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Significant Unobservable Inputs (Level 3) [Member] | Senior secured bank loan funds [Member] | Net Asset Valuation Technique [Member]
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|||
| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Assets, fair value | 21,000,000 | ||
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Significant Unobservable Inputs (Level 3) [Member] | Senior secured bank loan funds [Member] | Net Asset Valuation Technique [Member] | Weighted Average or Actual [Member]
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| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Estimated performance | 2.10% | ||
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Significant Unobservable Inputs (Level 3) [Member] | Hedge funds [Member] | Net Asset Valuation Technique [Member]
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| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Assets, fair value | 6,746,000 | ||
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Significant Unobservable Inputs (Level 3) [Member] | Hedge funds [Member] | Net Asset Valuation Technique [Member] | Minimum [Member]
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| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Estimated performance | 0.00% | ||
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Significant Unobservable Inputs (Level 3) [Member] | Hedge funds [Member] | Net Asset Valuation Technique [Member] | Maximum [Member]
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| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Estimated performance | 0.70% | ||
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Significant Unobservable Inputs (Level 3) [Member] | Hedge funds [Member] | Net Asset Valuation Technique [Member] | Weighted Average or Actual [Member]
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| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Estimated performance | 0.20% | ||
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Significant Unobservable Inputs (Level 3) [Member] | Miscellaneous other investments [Member] | Discounted Cash Flow Valuation Technique [Member]
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| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Assets, fair value | 1,340,000 | ||
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Significant Unobservable Inputs (Level 3) [Member] | Miscellaneous other investments [Member] | Discounted Cash Flow Valuation Technique [Member] | Weighted Average or Actual [Member]
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| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Credit spread | 7.50% | ||
| Illiquidity premium | 1.00% | ||
| Risk-free rate | 0.50% | ||
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Significant Unobservable Inputs (Level 3) [Member] | Other Investments [Member]
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| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Assets, fair value | 418,537,000 | ||
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Significant Unobservable Inputs (Level 3) [Member] | Assumed And Ceded Re Insurance Contracts Member | Internal Valuation Model Valuation Technique [Member]
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| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Other assets and (liabilities). fair value | 6,163,000 | ||
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Significant Unobservable Inputs (Level 3) [Member] | Assumed And Ceded Re Insurance Contracts Member | Internal Valuation Model Valuation Technique [Member] | Minimum [Member]
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| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Net premiums written | 0 | ||
| Contract period | 183 days | ||
| Net reserve for claims and claim expenses | 0 | ||
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Significant Unobservable Inputs (Level 3) [Member] | Assumed And Ceded Re Insurance Contracts Member | Internal Valuation Model Valuation Technique [Member] | Maximum [Member]
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| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Net premiums written | 6,000,000 | ||
| Contract period | 365 days | ||
| Net reserve for claims and claim expenses | 0 | ||
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Significant Unobservable Inputs (Level 3) [Member] | Energy And Weather Contracts [Member] | Spread Option, Quanto, Black Scholes and Simulation Valuation Techniques [Member]
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| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Other assets and (liabilities). fair value | 26,565,000 | ||
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Significant Unobservable Inputs (Level 3) [Member] | Energy And Weather Contracts [Member] | Spread Option, Quanto, Black Scholes and Simulation Valuation Techniques [Member] | Minimum [Member]
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| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Correlation | 0.00% | ||
| Volatility | 7.00% | ||
| Commodity curve | 1.77 | ||
| Weather curve | 19,000 | ||
| Counterparty default risk | 0.00% | ||
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Significant Unobservable Inputs (Level 3) [Member] | Energy And Weather Contracts [Member] | Spread Option, Quanto, Black Scholes and Simulation Valuation Techniques [Member] | Maximum [Member]
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| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Correlation | 100.00% | ||
| Volatility | 350.00% | ||
| Commodity curve | 66 | ||
| Weather curve | 5,000,000 | ||
| Counterparty default risk | 22.50% | ||
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Significant Unobservable Inputs (Level 3) [Member] | Other [Member] | Internal Valuation Model Valuation Technique [Member]
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| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Other assets and (liabilities). fair value | 1,250,000 | ||
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Significant Unobservable Inputs (Level 3) [Member] | Other [Member] | Net Asset Valuation Technique [Member]
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| Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] | |||
| Other assets and (liabilities). fair value | $ 14,167,000 | ||