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 |