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Investments (Net Investment Income) (Details) (USD $) In Thousands, unless otherwise specified | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2014 | Jun. 30, 2013 | Jun. 30, 2014 | Jun. 30, 2013
Net Investment Income [Line Items] |  |  |  |
Net investment income earned | $ 36,774 | $ 34,003 | $ 72,308 | $ 66,873
Fixed Income Securities [Member] |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Net investment income earned | 33,781 | 30,298 | 64,809 | 60,387
Equity Securities [Member] |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Net investment income earned | 1,736 | 1,874 | 3,185 | 3,081
Short-Term Investments [Member] |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Net investment income earned | 14 | 29 | 33 | 81
Other Investments [Member] |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Net investment income earned | 3,553 | 3,869 | 8,771 | 7,471
Investment Expenses [Member] |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Net investment income earned | $ (2,310) | $ (2,067) | $ (4,490) | $ (4,147)

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- Definition The income earned from investments in securities and other investments including dividends, interest, and returns on other investments. This item does not include realized gains (losses). + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration