Fair Value Measurement (Schedule Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Valuation Techniques) (Details) - USD ($) $ in Thousands | Jun. 30, 2016 | Dec. 31, 2015 |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | $ 3,487,837 | $ 3,380,642 |
Liabilities, Fair Value Disclosure, Recurring | 297,909 | 301,785 |
Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 502,370 | 478,197 |
Liabilities, Fair Value Disclosure, Recurring | 309 | 260 |
Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 2,976,495 | 2,892,014 |
Liabilities, Fair Value Disclosure, Recurring | 297,600 | 301,525 |
Level 3 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 8,972 | 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 | 12,926 | 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 | 2,526,666 | 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 | 47,694 | 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 | 238,327 | 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 | 84,593 | 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 | 29,288 | 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 | 12,926 | 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 | 2,526,666 | 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 | 47,694 | 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 | 238,327 | 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 | 84,593 | 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 | 29,288 | 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 | 328,365 | 280,263 |
Equity Securities [Member] | Nonredeemable Preferred Stock [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 29,702 | 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 | 8,972 | 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 | 328,365 | 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 | 29,702 | 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 | 8,972 | 10,431 |
Short-term Investments [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 90,635 | 79,841 |
Short-term Investments [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 70,410 | 69,991 |
Short-term Investments [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 20,225 | 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 | 90,669 | 105,436 |
Money Market Funds [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Assets, Fair Value Disclosure, Recurring | 90,669 | 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 | 7,600 | 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 | 7,600 | 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 | 309 | 260 |
Equity Contract [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Liabilities, Fair Value Disclosure, Recurring | 309 | 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 |