Fair Value Measurement (Schedule Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Valuation Techniques) (Details) - USD ($) $ in Thousands | Mar. 31, 2016 | Dec. 31, 2015 |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | $ 3,433,315 | $ 3,380,642 |
Liabilities, Fair Value Disclosure, Recurring | 300,059 | 301,785 |
Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 472,836 | 478,197 |
Liabilities, Fair Value Disclosure, Recurring | 262 | 260 |
Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 2,951,488 | 2,892,014 |
Liabilities, Fair Value Disclosure, Recurring | 299,797 | 301,525 |
Level 3 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 8,991 | 10,431 |
Liabilities, Fair Value Disclosure, Recurring | 0 | 0 |
Fixed maturity securities [Member] | US Treasury and Government [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 21,939 | 22,507 |
Fixed maturity securities [Member] | US States and Political Subdivisions Debt Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 2,531,777 | 2,505,040 |
Fixed maturity securities [Member] | Collateralized Mortgage Backed Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 56,532 | 49,838 |
Fixed maturity securities [Member] | Corporate Debt Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 260,917 | 243,372 |
Fixed maturity securities [Member] | Collateralized Debt Obligations [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 51,520 | 50,548 |
Fixed maturity securities [Member] | Collateralized Auto Loans [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 19,829 | 8,698 |
Fixed maturity securities [Member] | Level 1 [Member] | US Treasury and Government [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 21,939 | 22,507 |
Fixed maturity securities [Member] | Level 1 [Member] | US States and Political Subdivisions Debt Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 0 | 0 |
Fixed maturity securities [Member] | Level 1 [Member] | Collateralized Mortgage Backed Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 0 | 0 |
Fixed maturity securities [Member] | Level 1 [Member] | Corporate Debt Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 0 | 0 |
Fixed maturity securities [Member] | Level 1 [Member] | Collateralized Debt Obligations [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 0 | 0 |
Fixed maturity securities [Member] | Level 1 [Member] | Collateralized Auto Loans [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 0 | 0 |
Fixed maturity securities [Member] | Level 2 [Member] | US Treasury and Government [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 0 | 0 |
Fixed maturity securities [Member] | Level 2 [Member] | US States and Political Subdivisions Debt Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 2,531,777 | 2,505,040 |
Fixed maturity securities [Member] | Level 2 [Member] | Collateralized Mortgage Backed Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 56,532 | 49,838 |
Fixed maturity securities [Member] | Level 2 [Member] | Corporate Debt Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 260,917 | 243,372 |
Fixed maturity securities [Member] | Level 2 [Member] | Collateralized Debt Obligations [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 51,520 | 50,548 |
Fixed maturity securities [Member] | Level 2 [Member] | Collateralized Auto Loans [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 19,829 | 8,698 |
Fixed maturity securities [Member] | Level 3 [Member] | US Treasury and Government [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 0 | 0 |
Fixed maturity securities [Member] | Level 3 [Member] | US States and Political Subdivisions Debt Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 0 | 0 |
Fixed maturity securities [Member] | Level 3 [Member] | Collateralized Mortgage Backed Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 0 | 0 |
Fixed maturity securities [Member] | Level 3 [Member] | Corporate Debt Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 0 | 0 |
Fixed maturity securities [Member] | Level 3 [Member] | Collateralized Debt Obligations [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 0 | 0 |
Fixed maturity securities [Member] | Level 3 [Member] | Collateralized Auto Loans [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 0 | 0 |
Equity Securities [Member] | Common Stock [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 301,768 | 280,263 |
Equity Securities [Member] | Nonredeemable Preferred Stock [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 24,857 | 24,668 |
Equity Securities [Member] | Partnership Interest In Private Credit Fund [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 8,991 | 10,431 |
Equity Securities [Member] | Level 1 [Member] | Common Stock [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 301,768 | 280,263 |
Equity Securities [Member] | Level 1 [Member] | Nonredeemable Preferred Stock [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 0 | 0 |
Equity Securities [Member] | Level 1 [Member] | Partnership Interest In Private Credit Fund [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 0 | 0 |
Equity Securities [Member] | Level 2 [Member] | Common Stock [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 0 | 0 |
Equity Securities [Member] | Level 2 [Member] | Nonredeemable Preferred Stock [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 24,857 | 24,668 |
Equity Securities [Member] | Level 2 [Member] | Partnership Interest In Private Credit Fund [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 0 | 0 |
Equity Securities [Member] | Level 3 [Member] | Common Stock [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 0 | 0 |
Equity Securities [Member] | Level 3 [Member] | Nonredeemable Preferred Stock [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 0 | 0 |
Equity Securities [Member] | Level 3 [Member] | Partnership Interest In Private Credit Fund [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 8,991 | 10,431 |
Short-term Investments [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 76,436 | 79,841 |
Short-term Investments [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 70,380 | 69,991 |
Short-term Investments [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 6,056 | 9,850 |
Short-term Investments [Member] | Level 3 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 0 | 0 |
Money Market Funds [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 78,749 | 105,436 |
Money Market Funds [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 78,749 | 105,436 |
Money Market Funds [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 0 | 0 |
Money Market Funds [Member] | Level 3 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 0 | 0 |
Borrowings [Member] | Secured Debt [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities, Fair Value Disclosure, Recurring | 140,000 | 140,000 |
Borrowings [Member] | Unsecured Debt [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities, Fair Value Disclosure, Recurring | 150,000 | 150,000 |
Borrowings [Member] | Level 1 [Member] | Secured Debt [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities, Fair Value Disclosure, Recurring | 0 | 0 |
Borrowings [Member] | Level 1 [Member] | Unsecured Debt [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities, Fair Value Disclosure, Recurring | 0 | 0 |
Borrowings [Member] | Level 2 [Member] | Secured Debt [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities, Fair Value Disclosure, Recurring | 140,000 | 140,000 |
Borrowings [Member] | Level 2 [Member] | Unsecured Debt [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities, Fair Value Disclosure, Recurring | 150,000 | 150,000 |
Borrowings [Member] | Level 3 [Member] | Secured Debt [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities, Fair Value Disclosure, Recurring | 0 | 0 |
Borrowings [Member] | Level 3 [Member] | Unsecured Debt [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities, Fair Value Disclosure, Recurring | 0 | 0 |
Total Return Swap [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities, Fair Value Disclosure, Recurring | 9,797 | 11,525 |
Total Return Swap [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities, Fair Value Disclosure, Recurring | 0 | 0 |
Total Return Swap [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities, Fair Value Disclosure, Recurring | 9,797 | 11,525 |
Total Return Swap [Member] | Level 3 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities, Fair Value Disclosure, Recurring | 0 | 0 |
Equity Contract [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities, Fair Value Disclosure, Recurring | 262 | 260 |
Equity Contract [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities, Fair Value Disclosure, Recurring | 262 | 260 |
Equity Contract [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities, Fair Value Disclosure, Recurring | 0 | 0 |
Equity Contract [Member] | Level 3 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities, Fair Value Disclosure, Recurring | $ 0 | $ 0 |