Fair Value Measurement (Schedule Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Valuation Techniques) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	$ 3,380,642	$ 3,403,822
Fair value of liabilities measured on a recurring basis	301,785	294,219
Level 1 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	478,197	742,886
Fair value of liabilities measured on a recurring basis	260	194
Level 2 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	2,892,014	2,649,217
Fair value of liabilities measured on a recurring basis	301,525	294,025
Level 3 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	10,431	11,719
Fair value of liabilities measured on a recurring basis	0	0
Fixed Maturity Securities [Member] | US Treasury and Government [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	22,507	16,108
Fixed Maturity Securities [Member] | US Treasury and Government [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	22,507	16,108
Fixed Maturity Securities [Member] | US Treasury and Government [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	0	0
Fixed Maturity Securities [Member] | US Treasury and Government [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	0	0
Fixed Maturity Securities [Member] | US States and Political Subdivisions Debt Securities [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	2,505,040	2,275,455
Fixed Maturity Securities [Member] | US States and Political Subdivisions Debt Securities [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	0	0
Fixed Maturity Securities [Member] | US States and Political Subdivisions Debt Securities [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	2,505,040	2,275,455
Fixed Maturity Securities [Member] | US States and Political Subdivisions Debt Securities [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	0	0
Fixed Maturity Securities [Member] | Collateralized Mortgage Backed Securities [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	49,838	47,691
Fixed Maturity Securities [Member] | Collateralized Mortgage Backed Securities [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	0	0
Fixed Maturity Securities [Member] | Collateralized Mortgage Backed Securities [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	49,838	47,691
Fixed Maturity Securities [Member] | Collateralized Mortgage Backed Securities [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	0	0
Fixed Maturity Securities [Member] | Corporate Debt Securities [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	243,372	256,930
Fixed Maturity Securities [Member] | Corporate Debt Securities [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	0	0
Fixed Maturity Securities [Member] | Corporate Debt Securities [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	243,372	256,930
Fixed Maturity Securities [Member] | Corporate Debt Securities [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	0	0
Fixed Maturity Securities [Member] | Collateralized Debt Obligations [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	50,548	22,216
Fixed Maturity Securities [Member] | Collateralized Debt Obligations [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	0	0
Fixed Maturity Securities [Member] | Collateralized Debt Obligations [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	50,548	22,216
Fixed Maturity Securities [Member] | Collateralized Debt Obligations [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	0	0
Fixed Maturity Securities [Member] | Collateralized Auto Loans [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	8,698
Fixed Maturity Securities [Member] | Collateralized Auto Loans [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	0
Fixed Maturity Securities [Member] | Collateralized Auto Loans [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	8,698
Fixed Maturity Securities [Member] | Collateralized Auto Loans [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	0
Equity Securities [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	280,263	372,598
Equity Securities [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	280,263	372,598
Equity Securities [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	0	0
Equity Securities [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	0	0
Equity Securities [Member] | Nonredeemable Preferred Stock [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	24,668	28,563
Equity Securities [Member] | Nonredeemable Preferred Stock [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	0	0
Equity Securities [Member] | Nonredeemable Preferred Stock [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	24,668	28,563
Equity Securities [Member] | Nonredeemable Preferred Stock [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	0	0
Equity Securities [Member] | Private Equity Funds [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	10,431	11,719
Equity Securities [Member] | Private Equity Funds [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	0	0
Equity Securities [Member] | Private Equity Funds [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	0	0
Equity Securities [Member] | Private Equity Funds [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	10,431	11,719
Short-term Investments [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	79,841	88,361
Short-term Investments [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	69,991	69,999
Short-term Investments [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	9,850	18,362
Short-term Investments [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	0	0
Money Market Funds [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	105,436	284,181
Money Market Funds [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	105,436	284,181
Money Market Funds [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	0	0
Money Market Funds [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Fair value of assets measured on a recurring basis	0	0
Total Return Swap [Member]
Fair Value Measurement [Line Items]
Fair value of liabilities measured on a recurring basis	11,525	4,025
Total Return Swap [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Fair value of liabilities measured on a recurring basis	0	0
Total Return Swap [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Fair value of liabilities measured on a recurring basis	11,525	4,025
Total Return Swap [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Fair value of liabilities measured on a recurring basis	0	0
Equity Contract [Member]
Fair Value Measurement [Line Items]
Fair value of liabilities measured on a recurring basis	260	194
Equity Contract [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Fair value of liabilities measured on a recurring basis	260	194
Equity Contract [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Fair value of liabilities measured on a recurring basis	0	0
Equity Contract [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Fair value of liabilities measured on a recurring basis	0	0
Secured Debt [Member] | Borrowings [Member]
Fair Value Measurement [Line Items]
Fair value of liabilities measured on a recurring basis	140,000	140,000
Secured Debt [Member] | Borrowings [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Fair value of liabilities measured on a recurring basis	0	0
Secured Debt [Member] | Borrowings [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Fair value of liabilities measured on a recurring basis	140,000	140,000
Secured Debt [Member] | Borrowings [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Fair value of liabilities measured on a recurring basis	0	0
Unsecured Debt [Member] | Borrowings [Member]
Fair Value Measurement [Line Items]
Fair value of liabilities measured on a recurring basis	150,000	150,000
Unsecured Debt [Member] | Borrowings [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Fair value of liabilities measured on a recurring basis	0	0
Unsecured Debt [Member] | Borrowings [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Fair value of liabilities measured on a recurring basis	150,000	150,000
Unsecured Debt [Member] | Borrowings [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Fair value of liabilities measured on a recurring basis	$ 0	$ 0