Fair Value Measurements (Details) (USD $)
In Thousands, unless otherwise specified
Jun. 30, 2012
Dec. 31, 2011
Categories reported at fair value on a recurring basis    
Securities, Fair Value $ 2,853,434 $ 2,718,831
Percent of total 100.00% 100.00%
US Treasury Securities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 268,454 279,955
Other Policyholder Funds [Member]
   
Categories reported at fair value on a recurring basis    
Liabilities, fair value 278 (187)
U.S. Treasury securities and obligations of U.S. Government [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 135,892 134,437
Federal agencies [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 26,123 25,881
Federal agency issued residential mortgage-backed securities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 106,439 119,637
Corporate obligations [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 2,102,990 1,970,886
Corporate obligations [Member] | Industrial [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 544,941 486,880
Corporate obligations [Member] | Energy [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 193,676 171,711
Corporate obligations [Member] | Communications and Technology [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 219,485 201,393
Corporate obligations [Member] | Financial [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 316,822 318,078
Corporate obligations [Member] | Consumer [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 535,552 496,487
Corporate obligations [Member] | Public Utilities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 292,514 296,337
Corporate private-labeled residential mortgage-backed securities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 151,638 156,902
Municipal securities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 174,148 168,522
Others [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 103,178 94,656
Redeemable preferred stocks [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 15,842 11,221
Fixed maturity securities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 2,816,250 2,682,142
Equity securities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 37,184 36,689
GMWB [Member] | Other Policyholder Funds [Member]
   
Categories reported at fair value on a recurring basis    
Liabilities, fair value 278 (187)
Fixed maturity securities [Member] | US Treasury Securities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 268,454 279,955
Fixed maturity securities [Member] | U.S. Treasury securities and obligations of U.S. Government [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 135,892 134,437
Fixed maturity securities [Member] | Federal agencies [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 26,123 25,881
Fixed maturity securities [Member] | Federal agency issued residential mortgage-backed securities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 106,439 119,637
Fixed maturity securities [Member] | Corporate obligations [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 2,102,990 1,970,886
Fixed maturity securities [Member] | Corporate obligations [Member] | Industrial [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 544,941 486,880
Fixed maturity securities [Member] | Corporate obligations [Member] | Energy [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 193,676 171,711
Fixed maturity securities [Member] | Corporate obligations [Member] | Communications and Technology [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 219,485 201,393
Fixed maturity securities [Member] | Corporate obligations [Member] | Financial [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 316,822 318,078
Fixed maturity securities [Member] | Corporate obligations [Member] | Consumer [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 535,552 496,487
Fixed maturity securities [Member] | Corporate obligations [Member] | Public Utilities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 292,514 296,337
Fixed maturity securities [Member] | Corporate private-labeled residential mortgage-backed securities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 151,638 156,902
Fixed maturity securities [Member] | Municipal securities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 174,148 168,522
Fixed maturity securities [Member] | Others [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 103,178 94,656
Fixed maturity securities [Member] | Redeemable preferred stocks [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 15,842 11,221
Level 1 [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 30,754 26,313
Percent of total 1.00% 1.00%
Level 1 [Member] | Other Policyholder Funds [Member]
   
Categories reported at fair value on a recurring basis    
Liabilities, fair value      
Level 1 [Member] | Fixed maturity securities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 28,623 24,097
Level 1 [Member] | Equity securities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 2,131 2,216
Level 1 [Member] | GMWB [Member] | Other Policyholder Funds [Member]
   
Categories reported at fair value on a recurring basis    
Liabilities, fair value      
Level 1 [Member] | Fixed maturity securities [Member] | US Treasury Securities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 12,781 12,876
Level 1 [Member] | Fixed maturity securities [Member] | U.S. Treasury securities and obligations of U.S. Government [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 12,781 12,876
Level 1 [Member] | Fixed maturity securities [Member] | Federal agencies [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value     
Level 1 [Member] | Fixed maturity securities [Member] | Redeemable preferred stocks [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 15,842 11,221
Level 2 [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 2,776,532 2,647,636
Percent of total 97.00% 97.00%
Level 2 [Member] | Other Policyholder Funds [Member]
   
Categories reported at fair value on a recurring basis    
Liabilities, fair value      
Level 2 [Member] | Fixed maturity securities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 2,742,628 2,614,286
Level 2 [Member] | Equity securities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 33,904 33,350
Level 2 [Member] | GMWB [Member] | Other Policyholder Funds [Member]
   
Categories reported at fair value on a recurring basis    
Liabilities, fair value      
Level 2 [Member] | Fixed maturity securities [Member] | US Treasury Securities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 252,553 263,648
Level 2 [Member] | Fixed maturity securities [Member] | U.S. Treasury securities and obligations of U.S. Government [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 119,991 118,130
Level 2 [Member] | Fixed maturity securities [Member] | Federal agencies [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 26,123 25,881
Level 2 [Member] | Fixed maturity securities [Member] | Federal agency issued residential mortgage-backed securities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 106,439 119,637
Level 2 [Member] | Fixed maturity securities [Member] | Corporate obligations [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 2,065,475 1,935,469
Level 2 [Member] | Fixed maturity securities [Member] | Corporate obligations [Member] | Industrial [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 542,488 486,380
Level 2 [Member] | Fixed maturity securities [Member] | Corporate obligations [Member] | Energy [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 191,293 169,342
Level 2 [Member] | Fixed maturity securities [Member] | Corporate obligations [Member] | Communications and Technology [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 219,485 201,393
Level 2 [Member] | Fixed maturity securities [Member] | Corporate obligations [Member] | Financial [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 305,180 307,464
Level 2 [Member] | Fixed maturity securities [Member] | Corporate obligations [Member] | Consumer [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 514,515 474,553
Level 2 [Member] | Fixed maturity securities [Member] | Corporate obligations [Member] | Public Utilities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 292,514 296,337
Level 2 [Member] | Fixed maturity securities [Member] | Corporate private-labeled residential mortgage-backed securities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 151,638 156,902
Level 2 [Member] | Fixed maturity securities [Member] | Municipal securities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 169,784 163,611
Level 2 [Member] | Fixed maturity securities [Member] | Others [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 103,178 94,656
Level 2 [Member] | Fixed maturity securities [Member] | Redeemable preferred stocks [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value      
Level 3 [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 46,148 44,882
Percent of total 2.00% 2.00%
Level 3 [Member] | Other Policyholder Funds [Member]
   
Categories reported at fair value on a recurring basis    
Liabilities, fair value 278 (187)
Level 3 [Member] | Fixed maturity securities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 44,999 43,759
Level 3 [Member] | Equity securities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 1,149 1,123
Level 3 [Member] | GMWB [Member] | Other Policyholder Funds [Member]
   
Categories reported at fair value on a recurring basis    
Liabilities, fair value 278 (187)
Level 3 [Member] | Fixed maturity securities [Member] | US Treasury Securities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 3,120 3,431
Level 3 [Member] | Fixed maturity securities [Member] | U.S. Treasury securities and obligations of U.S. Government [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 3,120 3,431
Level 3 [Member] | Fixed maturity securities [Member] | Federal agencies [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value     
Level 3 [Member] | Fixed maturity securities [Member] | Corporate obligations [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 37,515 35,417
Level 3 [Member] | Fixed maturity securities [Member] | Corporate obligations [Member] | Industrial [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 2,453 500
Level 3 [Member] | Fixed maturity securities [Member] | Corporate obligations [Member] | Energy [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 2,383 2,369
Level 3 [Member] | Fixed maturity securities [Member] | Corporate obligations [Member] | Communications and Technology [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value      
Level 3 [Member] | Fixed maturity securities [Member] | Corporate obligations [Member] | Financial [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 11,642 10,614
Level 3 [Member] | Fixed maturity securities [Member] | Corporate obligations [Member] | Consumer [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 21,037 21,934
Level 3 [Member] | Fixed maturity securities [Member] | Corporate obligations [Member] | Public Utilities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value      
Level 3 [Member] | Fixed maturity securities [Member] | Corporate private-labeled residential mortgage-backed securities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value      
Level 3 [Member] | Fixed maturity securities [Member] | Municipal securities [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value 4,364 4,911
Level 3 [Member] | Fixed maturity securities [Member] | Others [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value      
Level 3 [Member] | Fixed maturity securities [Member] | Redeemable preferred stocks [Member]
   
Categories reported at fair value on a recurring basis    
Securities, Fair Value