Schedule 1 Summary of Investments (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	$ 5,716,347
Amount shown in Balance Sheet	6,049,750
Fixed Maturities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	5,546,534
Fair Value	5,881,970
Amount shown in Balance Sheet	5,879,936
Available For Sale Fixed Maturities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	5,385,432
Fair Value	5,718,834
Amount shown in Balance Sheet	5,718,834
US Government Agencies Debt Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	285,166
Fair Value	295,679
Amount shown in Balance Sheet	295,679
US States and Political Subdivisions Debt Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	999,940
Fair Value	1,085,341
Amount shown in Balance Sheet	1,085,341
Special Purpose Revenue Bonds Of States Municipalities And Political Subdivisions [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	1,741,297
Fair Value	1,863,888
Amount shown in Balance Sheet	1,863,888
Corporate Debt Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	817,886
Fair Value	846,333
Amount shown in Balance Sheet	846,333
Residential Mortgage Backed Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	1,036,436
Fair Value	1,100,086
Amount shown in Balance Sheet	1,100,086
Commercial Mortgage Backed Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	244,535
Fair Value	256,124
Amount shown in Balance Sheet	256,124
Asset-backed Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	34,655
Fair Value	34,746
Amount shown in Balance Sheet	34,746
Foreign Government Debt Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	225,517
Fair Value	236,637
Amount shown in Balance Sheet	236,637
Held To Maturity Fixed Maturities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	161,102
Fair Value	163,136
Amount shown in Balance Sheet	161,102
Held To Maturity Us Government Agencies Debt Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	6,998
Fair Value	7,067
Amount shown in Balance Sheet	6,998
Held To Maturity Corporate Debt Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	110,284
Fair Value	111,643
Amount shown in Balance Sheet	110,284
Held To Maturity Foreign Government Debt Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	43,820
Fair Value	44,426
Amount shown in Balance Sheet	43,820
Equity Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	38,053
Fair Value	35,720
Amount shown in Balance Sheet	35,720
Banks, Trust and Insurance, Equities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	38,037
Fair Value	35,703
Amount shown in Balance Sheet	35,703
Industrial, Miscellaneous, and All Others [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	16
Fair Value	17
Amount shown in Balance Sheet	17
Short Term Investments Schedule One [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	133,917
Amount shown in Balance Sheet	133,917
Other Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	35,880
Amount shown in Balance Sheet	$ 35,880