Investments (Components Of Net Investment Income) (Details) (USD $) In Thousands | 3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2011 | Sep. 30, 2010 | Sep. 30, 2011 | Sep. 30, 2010 | |
| Investment income before investment expenses | $ (25,414) | $ 62,398 | $ 73,567 | $ 159,296 |
| Investment expenses | (2,526) | (2,828) | (7,898) | (7,844) |
| Net investment (loss) income | (27,940) | 59,570 | 65,669 | 151,452 |
Fixed Maturity Investments [Member] | ||||
| Components Of Net Investment Income | 11,435 | 35,219 | 63,774 | 92,108 |
Short-Term Investments [Member] | ||||
| Components Of Net Investment Income | 281 | 635 | 1,309 | 1,803 |
Equity Securities [Member] | ||||
| Components Of Net Investment Income | 171 | 297 | ||
Other Investments, Other [Member] | ||||
| Components Of Net Investment Income | (11,665) | 18,979 | 2,000 | 32,013 |
Cash And Cash Equivalents [Member] | ||||
| Components Of Net Investment Income | 66 | 74 | 152 | 157 |
Other Investments Hedge Funds And Private Equity Investments [Member] | ||||
| Components Of Net Investment Income | $ (25,702) | $ 7,491 | $ 6,035 | $ 33,215 |