SCHEDULE I-SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	$ 4,188,734
Fair Value	4,230,275
Amount at which shown in the balance sheet	4,230,275
Equity Securities, Common Stocks [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	2,797
Fair Value	2,936
Amount at which shown in the balance sheet	2,936
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	2,797
Fair Value	2,936
Amount at which shown in the balance sheet	2,936
Fixed Maturities, Bonds [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	4,185,937
Fair Value	4,227,339
Amount at which shown in the balance sheet	4,227,339
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	863,282
Fair Value	866,251
Amount at which shown in the balance sheet	866,251
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	795,935
Fair Value	812,394
Amount at which shown in the balance sheet	812,394
Fixed Maturities, Bonds [Member] | Foreign Governments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	132,490
Fair Value	142,066
Amount at which shown in the balance sheet	142,066
Fixed Maturities, Bonds [Member] | Public Utilities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	115,561
Fair Value	116,988
Amount at which shown in the balance sheet	116,988
Fixed Maturities, Bonds [Member] | Mortgage Backed Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	601,584
Fair Value	601,251
Amount at which shown in the balance sheet	601,251
Fixed Maturities, Bonds [Member] | All Other Corporate Bonds [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	1,677,085
Fair Value	1,688,389
Amount at which shown in the balance sheet	$ 1,688,389