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Losses And Loss Adjustment Expenses (Narrative) (Details) (USD $) | 12 Months Ended
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Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010
Extraordinary Item [Line Items] |  |  |
Increase in provision for insured events of prior years in 2012 | $ 42,332,000 | $ 18,494,000 | $ (13,058,000)
Increase in provision for insured events |  | 18,000,000 |
Decrease in provision for insured events |  |  | 13,000,000
Unfavorable development |  |  | 3,000,000
Catastrophe [Member] |  |  |
Extraordinary Item [Line Items] |  |  |
Pre-tax catastrophe losses | $ 39,000,000 | $ 18,000,000 | $ 25,000,000

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