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Investments (Held-To-Maturity Securities Disclosure) (Details) (USD $) | 12 Months Ended
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Dec. 31, 2011 years securities | Dec. 31, 2010 | Dec. 31, 2009
Amortized Cost | $ 706,782,000 | $ 1,199,801,000 |  |
Net Unrealized Gains (Losses) | 5,566,000 | 14,523,000 |  |
Carrying Value | 712,348,000 | 1,214,324,000 |  |
Unrecognized Holding Gains | 45,946,000 | 43,998,000 |  |
Unrecognized Holding Losses | (251,000) | (2,028,000) |  |
Fair Value | 758,043,000 | 1,256,294,000 |  |
Held To Maturity securities average duration | 2.9 |  |  |
Number of held to maturity securities transferred to available-for-sale | 105 |  |  |
Securities reclassified from the HTM category to AFS carrying value | 323,100,000 |  |  |
Securities reclassified from the HTM category to AFS net unrecognized gain | 18,700,000 |  |  |
Redemption and maturities of fixed maturity securities, held-to-maturity | 177,350,000 | 319,835,000 |  | 282,310,000
U.S. Government and Government Agencies [Member] |  |  |  |
Amortized Cost |  | 93,411,000 |  |
Net Unrealized Gains (Losses) |  | 4,695,000 |  |
Carrying Value |  | 98,106,000 |  |
Unrecognized Holding Gains |  | 5,023,000 |  |
Unrecognized Holding Losses |  | 0 |  |
Fair Value |  | 103,129,000 |  |
Foreign Government [Member] |  |  |  |
Amortized Cost | 5,292,000 | 5,292,000 |  |
Net Unrealized Gains (Losses) | 292,000 | 368,000 |  |
Carrying Value | 5,584,000 | 5,660,000 |  |
Unrecognized Holding Gains | 0 | 0 |  |
Unrecognized Holding Losses | (88,000) | (30,000) |  |
Fair Value | 5,496,000 | 5,630,000 |  |
Obligations of States and Political Subdivisions [Member] |  |  |  |
Amortized Cost | 614,118,000 | 874,388,000 |  |
Net Unrealized Gains (Losses) | 11,894,000 | 22,183,000 |  |
Carrying Value | 626,012,000 | 896,571,000 |  |
Unrecognized Holding Gains | 31,529,000 | 16,845,000 |  |
Unrecognized Holding Losses | (156,000) | (1,132,000) |  |
Fair Value | 657,385,000 | 912,284,000 |  |
Corporate Securities [Member] |  |  |  |
Amortized Cost | 64,840,000 | 76,663,000 |  |
Net Unrealized Gains (Losses) | (2,189,000) | (3,990,000) |  |
Carrying Value | 62,651,000 | 72,673,000 |  |
Unrecognized Holding Gains | 6,887,000 | 9,705,000 |  |
Unrecognized Holding Losses | 0 | (313,000) |  |
Fair Value | 69,538,000 | 82,065,000 |  |
Asset-backed Securities ("ABS") [Member] |  |  |  |
Amortized Cost | 8,077,000 | 12,947,000 |  |
Net Unrealized Gains (Losses) | (1,469,000) | (2,422,000) |  |
Carrying Value | 6,608,000 | 10,525,000 |  |
Unrecognized Holding Gains | 1,353,000 | 1,847,000 |  |
Unrecognized Holding Losses | (7,000) | (444,000) |  |
Fair Value | 7,954,000 | 11,928,000 |  |
Commercial Mortgage-backed Securities ("CMBS") [Member] |  |  |  |
Amortized Cost | 14,455,000 | 54,909,000 | [1] |
Net Unrealized Gains (Losses) | (2,962,000) | (7,354,000) | [1] |
Carrying Value | 11,493,000 | 47,555,000 | [1] |
Unrecognized Holding Gains | 6,177,000 | 7,483,000 | [1] |
Unrecognized Holding Losses | 0 | (109,000) | [1] |
Fair Value | 17,670,000 | 54,929,000 | [1] |
Government Guaranteed Agency Securities Carrying Value |  | 8,900,000 |  |
Residential Mortgage Backed Securities ("RMBS") [Member] |  |  |  |
Amortized Cost |  | 82,191,000 | [2] |
Net Unrealized Gains (Losses) |  | 1,043,000 | [2] |
Carrying Value |  | 83,234,000 | [2] |
Unrecognized Holding Gains |  | 3,095,000 | [2] |
Unrecognized Holding Losses |  | 0 | [2] |
Fair Value |  | 86,329,000 | [2] |
Government Guaranteed Agency Securities Carrying Value |  | $ 4,000,000 |  |
[1] | 1 CMBS includes government guaranteed agency securities with a carrying value $8.9 million at December 31, 2010.
[2] | 2 RMBS includes government guaranteed agency securities with a carrying value $4.0 million at December 31, 2010.

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