v2.3.0.15
Fair Value Measurements (Balances Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) (USD $)
In Thousands
Sep. 30, 2011
Dec. 31, 2010
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities$ 5,576,584$ 5,431,226
Total equity securities1,609,1991,721,971
Short-term investments491,756325,340
Total investments available-for-sale7,677,5397,478,537
Derivative contracts27,91525,228
Residential Mortgage-Backed Securities [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities417,954425,563
Residential Mortgage-Backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities00
Residential Mortgage-Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities417,954425,563
Residential Mortgage-Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities00
U.S. Treasury Securities And Obligations Of U.S. Government Agencies [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities308,159321,338
U.S. Treasury Securities And Obligations Of U.S. Government Agencies [Member] | Fair Value, Inputs, Level 1 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities00
U.S. Treasury Securities And Obligations Of U.S. Government Agencies [Member] | Fair Value, Inputs, Level 2 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities308,159321,338
U.S. Treasury Securities And Obligations Of U.S. Government Agencies [Member] | Fair Value, Inputs, Level 3 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities00
Obligations Of States, Municipalities And Political Subdivisions [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities2,918,1632,799,339
Obligations Of States, Municipalities And Political Subdivisions [Member] | Fair Value, Inputs, Level 1 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities00
Obligations Of States, Municipalities And Political Subdivisions [Member] | Fair Value, Inputs, Level 2 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities2,918,1632,799,339
Obligations Of States, Municipalities And Political Subdivisions [Member] | Fair Value, Inputs, Level 3 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities00
Asset-Backed Securities [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities17,55222,756
Asset-Backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities00
Asset-Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities17,55222,756
Asset-Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities00
Convertible Bonds [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities 16,725
Convertible Bonds [Member] | Fair Value, Inputs, Level 1 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities 0
Convertible Bonds [Member] | Fair Value, Inputs, Level 2 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities 16,725
Convertible Bonds [Member] | Fair Value, Inputs, Level 3 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities 0
Public Utilities [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities76,107102,444
Public Utilities [Member] | Fair Value, Inputs, Level 1 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities00
Public Utilities [Member] | Fair Value, Inputs, Level 2 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities76,107102,444
Public Utilities [Member] | Fair Value, Inputs, Level 3 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities00
Insurance Companies, Banks And Trusts [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total equity securities612,395710,986
Insurance Companies, Banks And Trusts [Member] | Fair Value, Inputs, Level 1 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total equity securities612,395710,986
Insurance Companies, Banks And Trusts [Member] | Fair Value, Inputs, Level 2 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total equity securities00
Insurance Companies, Banks And Trusts [Member] | Fair Value, Inputs, Level 3 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total equity securities00
Industrial, Consumer And All Other [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total equity securities996,8041,010,985
Industrial, Consumer And All Other [Member] | Fair Value, Inputs, Level 1 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total equity securities996,8041,010,985
Industrial, Consumer And All Other [Member] | Fair Value, Inputs, Level 2 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total equity securities00
Industrial, Consumer And All Other [Member] | Fair Value, Inputs, Level 3 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total equity securities00
Foreign Governments [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities740,363572,818
Foreign Governments [Member] | Fair Value, Inputs, Level 1 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities00
Foreign Governments [Member] | Fair Value, Inputs, Level 2 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities740,363572,818
Foreign Governments [Member] | Fair Value, Inputs, Level 3 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities00
All Other Corporate Bonds [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities1,098,2861,170,243
All Other Corporate Bonds [Member] | Fair Value, Inputs, Level 1 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities00
All Other Corporate Bonds [Member] | Fair Value, Inputs, Level 2 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities1,098,2861,170,243
All Other Corporate Bonds [Member] | Fair Value, Inputs, Level 3 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities00
Fair Value, Inputs, Level 1 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities00
Total equity securities1,609,1991,721,971
Short-term investments428,681269,466
Total investments available-for-sale2,037,8801,991,437
Derivative contracts00
Fair Value, Inputs, Level 2 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities5,576,5845,431,226
Total equity securities00
Short-term investments63,07555,874
Total investments available-for-sale5,639,6595,487,100
Derivative contracts00
Fair Value, Inputs, Level 3 [Member]
  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total fixed maturities00
Total equity securities00
Short-term investments00
Total investments available-for-sale00
Derivative contracts$ 27,915$ 25,228