SCHEDULE I-SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	$ 5,703,560
Fair Value	5,823,647
Amount at which shown in the balance sheet	5,823,647
Equity Securities, Common Stocks [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	2,666
Fair Value	2,747
Amount at which shown in the balance sheet	2,747
Equity Securities, Common Stocks [Member] | Industrial, Miscellaneous, and All Others [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	2,666
Fair Value	2,747
Amount at which shown in the balance sheet	2,747
Fixed Maturities, Bonds [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	5,700,894
Fair Value	5,820,900
Amount at which shown in the balance sheet	5,820,900
Fixed Maturities, Bonds [Member] | US Government and Government Agencies and Authorities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	592,108
Fair Value	597,037
Amount at which shown in the balance sheet	597,037
Fixed Maturities, Bonds [Member] | States, Municipalities and Political Subdivisions [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	2,255,192
Fair Value	2,323,471
Amount at which shown in the balance sheet	2,323,471
Fixed Maturities, Bonds [Member] | Foreign Governments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	146,755
Fair Value	157,190
Amount at which shown in the balance sheet	157,190
Fixed Maturities, Bonds [Member] | Public Utilities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	317,977
Fair Value	323,982
Amount at which shown in the balance sheet	323,982
Fixed Maturities, Bonds [Member] | Mortgage Backed Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	699,119
Fair Value	710,351
Amount at which shown in the balance sheet	710,351
Fixed Maturities, Bonds [Member] | All Other Corporate Bonds [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	1,689,743
Fair Value	1,708,869
Amount at which shown in the balance sheet	$ 1,708,869