Fair Value (Fair Value Measurement Levels For All Assets, Recorded At Fair And Market Value) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	$ 5,531,410	$ 5,107,028
Fixed maturities - available for sale, at fair value	41,470	113,606
Equity securities - available for sale, at market value	13	10
Equity securities - available for sale, at fair value	1,199,848	1,207,053
Other invested assets, at fair value	1,068,711	817,352
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities - available for sale, at market value	13	10
Equity securities - available for sale, at fair value	1,059,288	1,090,959
Other invested assets, at fair value	1,068,711	817,352
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	5,485,737	5,088,439
Fixed maturities - available for sale, at fair value	41,470	113,606
Equity securities - available for sale, at fair value	140,560	116,094
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	45,673	18,589
U.S. Treasury Securities And Obligations Of U.S. Government Agencies And Corporations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	78,190	79,539
U.S. Treasury Securities And Obligations Of U.S. Government Agencies And Corporations [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	78,190	79,539
States, Municipalities And Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	1,291,963	1,660,905
States, Municipalities And Political Subdivisions [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	1,291,963	1,660,905
Corporate Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	1,564,852	1,228,235
Corporate Debt Securities [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	1,564,852	1,228,235
Asset-backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	46,487	45,103
Asset-backed Securities [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	41,638	29,057
Asset-backed Securities [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	4,849	16,046
Mortgage-Backed Securities Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	52,624	47,874
Mortgage-Backed Securities Commercial [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	52,624	47,874
Agency Residential [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	683,722	543,393
Agency Residential [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	654,324	543,393
Agency Residential [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	29,398
Non-agency Residential [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	2,329	24,289
Non-agency Residential [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	2,324	24,282
Non-agency Residential [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	5	7
Foreign Government Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	780,003	788,649
Foreign Government Securities [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	780,003	788,649
Foreign Corporate Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	1,031,240	689,041
Foreign Corporate Securities [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	1,019,819	686,505
Foreign Corporate Securities [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	$ 11,421	$ 2,536

Amount of debt securities categorized neither as held-to-maturity nor trading.

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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Reference 9: http://www.xbrl.org/2003/role/presentationRef

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+ Details

- Definition

Amount of equity securities categorized neither as held-to-maturity nor as trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 3

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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+ Details