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Investments (Available-For-Sale Securities Disclosure) (Details) (USD $) | Dec. 31, 2011 | Dec. 31, 2010
--- | --- | ---
Cost/Amortized Cost | $ 2,910,682,000 |  | $ 2,344,027,000 |
Unrealized Gains | 153,512,000 |  | 83,786,000 |
Unrealized Losses | (9,466,000) |  | (15,435,000) |
Fair Value | 3,054,728,000 |  | 2,412,378,000 |
Corporate securities fully guaranteed by the Federal Deposit Insurance Corporation ("FDIC") | 76,500,000 |  | 121,000,000 |
AFS Fixed Maturity Securities [Member] |  |  |  |
Cost/Amortized Cost | 2,766,856,000 |  | 2,285,988,000 |
Unrealized Gains | 139,895,000 |  | 72,189,000 |
Unrealized Losses | (9,378,000) |  | (15,435,000) |
Fair Value | 2,897,373,000 |  | 2,342,742,000 |
AFS Fixed Maturity Securities [Member] | U.S. Government and Government Agencies [Member] |  |  |  |
Cost/Amortized Cost | 333,504,000 | [1] | 312,384,000 | [1]
Unrealized Gains | 20,292,000 | [1] | 8,292,000 | [1]
Unrealized Losses | 0 | [1] | (147,000) | [1]
Fair Value | 353,796,000 | [1] | 320,529,000 | [1]
AFS Fixed Maturity Securities [Member] | Foreign Government [Member] |  |  |  |
Cost/Amortized Cost | 33,687,000 |  | 19,035,000 |
Unrealized Gains | 1,042,000 |  | 280,000 |
Unrealized Losses | (556,000) |  | (349,000) |
Fair Value | 34,173,000 |  | 18,966,000 |
AFS Fixed Maturity Securities [Member] | Obligations of States and Political Subdivisions [Member] |  |  |  |
Cost/Amortized Cost | 578,214,000 |  | 512,013,000 |
Unrealized Gains | 44,491,000 |  | 22,534,000 |
Unrealized Losses | (46,000) |  | (650,000) |
Fair Value | 622,659,000 |  | 533,897,000 |
AFS Fixed Maturity Securities [Member] | Corporate Securities [Member] |  |  |  |
Cost/Amortized Cost | 1,168,439,000 |  | 973,835,000 |
Unrealized Gains | 50,167,000 |  | 28,674,000 |
Unrealized Losses | (5,296,000) |  | (8,784,000) |
Fair Value | 1,213,310,000 |  | 993,725,000 |
AFS Fixed Maturity Securities [Member] | Asset-backed Securities ("ABS") [Member] |  |  |  |
Cost/Amortized Cost | 77,706,000 |  | 48,558,000 |
Unrealized Gains | 1,289,000 |  | 514,000 |
Unrealized Losses | (46,000) |  | (339,000) |
Fair Value | 78,949,000 |  | 48,733,000 |
AFS Fixed Maturity Securities [Member] | Commercial Mortgage-backed Securities ("CMBS") [Member] |  |  |  |
Cost/Amortized Cost | 107,838,000 | [2] | 103,374,000 | [2]
Unrealized Gains | 6,427,000 | [2] | 4,024,000 | [2]
Unrealized Losses | (1,667,000) | [2] | (2,923,000) | [2]
Fair Value | 112,598,000 | [2] | 104,475,000 | [2]
Government guaranteed agency securities fair value | 72,900,000 |  | 71,900,000 |
AFS Fixed Maturity Securities [Member] | Residential Mortgage Backed Securities ("RMBS") [Member] |  |  |  |
Cost/Amortized Cost | 467,468,000 | [3] | 316,789,000 | [3]
Unrealized Gains | 16,187,000 | [3] | 7,871,000 | [3]
Unrealized Losses | (1,767,000) | [3] | (2,243,000) | [3]
Fair Value | 481,888,000 | [3] | 322,417,000 | [3]
Government guaranteed agency securities fair value | 98,200,000 |  | 91,100,000 |
Equity Securities [Member] |  |  |  |
Cost/Amortized Cost | 143,826,000 |  | 58,039,000 |
Unrealized Gains | 13,617,000 |  | 11,597,000 |
Unrealized Losses | (88,000) |  | 0 |
Fair Value | $ 157,355,000 |  | $ 69,636,000 |
[1] | 1 U.S. government includes corporate securities fully guaranteed by the Federal Deposit Insurance Corporation ("FDIC") with a fair value of $76.5 million at December 31, 2011 and $121.0 million at December 31, 2010.
[2] | 2 CMBS includes government guaranteed agency securities with a fair value of $72.9 million at December 31, 2011 and $71.9 million at December 31, 2010.
[3] | 3 RMBS includes government guaranteed agency securities with a fair value of $98.2 million at December 31, 2011 and $91.1 million at December 31, 2010.

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