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Investments (Available-For-Sale Securities Disclosure) (Details) (USD $) | Dec. 31, 2013 | Dec. 31, 2012
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Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Cost/Amortized Cost | $ 3,831,327,000 |  | $ 3,263,124,000 |
Unrealized Gains | 128,951,000 |  | 187,105,000 |
Unrealized Losses | (51,971,000) |  | (2,834,000) |
Fair Value | 3,908,307,000 |  | 3,447,395,000 |
AFS Fixed Maturity Securities [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Cost/Amortized Cost | 3,675,977,000 |  | 3,130,683,000 |
Unrealized Gains | 91,434,000 |  | 167,705,000 |
Unrealized Losses | (51,875,000) |  | (2,375,000) |
Fair Value | 3,715,536,000 |  | 3,296,013,000 |
AFS Fixed Maturity Securities [Member] | U.S. Government and Government Agencies [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Cost/Amortized Cost | 163,218,000 |  | 241,874,000 |
Unrealized Gains | 10,661,000 |  | 17,219,000 |
Unrealized Losses | (504,000) |  | (1,000) |
Fair Value | 173,375,000 |  | 259,092,000 |
AFS Fixed Maturity Securities [Member] | Foreign Government [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Cost/Amortized Cost | 29,781,000 |  | 28,813,000 |
Unrealized Gains | 906,000 |  | 1,540,000 |
Unrealized Losses | (72,000) |  | (124,000) |
Fair Value | 30,615,000 |  | 30,229,000 |
AFS Fixed Maturity Securities [Member] | Obligations of States and Political Subdivisions [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Cost/Amortized Cost | 946,455,000 |  | 773,953,000 |
Unrealized Gains | 25,194,000 |  | 44,398,000 |
Unrealized Losses | (20,025,000) |  | (327,000) |
Fair Value | 951,624,000 |  | 818,024,000 |
AFS Fixed Maturity Securities [Member] | Corporate Securities [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Cost/Amortized Cost | 1,707,928,000 |  | 1,368,954,000 |
Unrealized Gains | 44,004,000 |  | 81,696,000 |
Unrealized Losses | (17,049,000) |  | (402,000) |
Fair Value | 1,734,883,000 |  | 1,450,248,000 |
AFS Fixed Maturity Securities [Member] | Asset-backed Securities [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Cost/Amortized Cost | 140,430,000 |  | 126,330,000 |
Unrealized Gains | 934,000 |  | 2,319,000 |
Unrealized Losses | (468,000) |  | (9,000) |
Fair Value | 140,896,000 |  | 128,640,000 |
AFS Fixed Maturity Securities [Member] | Commercial Mortgage Backed Securities [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Cost/Amortized Cost | 172,288,000 | [1] | 133,763,000 | [1]
Unrealized Gains | 2,462,000 | [1] | 4,572,000 | [1]
Unrealized Losses | (3,466,000) | [1] | (1,216,000) | [1]
Fair Value | 171,284,000 | [1] | 137,119,000 | [1]
Government guaranteed agency securities fair value | 30,000,000 |  | 48,900,000 |
AFS Fixed Maturity Securities [Member] | Residential Mortgage Backed Securities [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Cost/Amortized Cost | 515,877,000 | [2] | 456,996,000 | [2]
Unrealized Gains | 7,273,000 | [2] | 15,961,000 | [2]
Unrealized Losses | (10,291,000) | [2] | (296,000) | [2]
Fair Value | 512,859,000 | [2] | 472,661,000 | [2]
Government guaranteed agency securities fair value | 55,200,000 |  | 91,000,000 |
Equity Securities [Member] |  |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |  |
Cost/Amortized Cost | 155,350,000 |  | 132,441,000 |
Unrealized Gains | 37,517,000 |  | 19,400,000 |
Unrealized Losses | (96,000) |  | (459,000) |
Fair Value | $ 192,771,000 |  | $ 151,382,000 |
[1] | CMBS includes government guaranteed agency securities with a fair value of $30.0 million at December 31, 2013 and $48.9 million at December 31, 2012
[2] | RMBS includes government guaranteed agency securities with a fair value of $55.2 million at December 31, 2013 and $91.0 million at December 31, 2012.

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