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