Fair Value Measurement (Schedule Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Valuation Techniques) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	$ 3,348,386	$ 3,403,822
Liabilities, Fair Value Disclosure, Recurring	296,325	294,219
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	448,176	742,886
Liabilities, Fair Value Disclosure, Recurring	266	194
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	2,888,514	2,649,217
Liabilities, Fair Value Disclosure, Recurring	296,059	294,025
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	11,696	11,719
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	25,150	16,108
Fixed maturity securities [Member] | US Treasury and Government [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	25,150	16,108
Fixed maturity securities [Member] | US Treasury and Government [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0
Fixed maturity securities [Member] | US Treasury and Government [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0
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	2,495,881	2,275,455
Fixed maturity securities [Member] | US States and Political Subdivisions Debt Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0
Fixed maturity securities [Member] | US States and Political Subdivisions Debt Securities [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	2,495,881	2,275,455
Fixed maturity securities [Member] | US States and Political Subdivisions Debt Securities [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0
Fixed maturity securities [Member] | Collateralized Mortgage Backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	63,045	47,691
Fixed maturity securities [Member] | Collateralized Mortgage Backed Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0
Fixed maturity securities [Member] | Collateralized Mortgage Backed Securities [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	63,045	47,691
Fixed maturity securities [Member] | Collateralized Mortgage Backed Securities [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0
Fixed maturity securities [Member] | Corporate Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	248,246	256,930
Fixed maturity securities [Member] | Corporate Debt Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0
Fixed maturity securities [Member] | Corporate Debt Securities [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	248,246	256,930
Fixed maturity securities [Member] | Corporate Debt Securities [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0
Fixed maturity securities [Member] | Collateralized Debt Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	49,665	22,216
Fixed maturity securities [Member] | Collateralized Debt Obligations [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0
Fixed maturity securities [Member] | Collateralized Debt Obligations [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	49,665	22,216
Fixed maturity securities [Member] | Collateralized Debt Obligations [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0
Fixed maturity securities [Member] | Collateralized Auto Loans [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	4,877
Fixed maturity securities [Member] | Collateralized Auto Loans [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	0
Fixed maturity securities [Member] | Collateralized Auto Loans [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	4,877
Fixed maturity securities [Member] | Collateralized Auto Loans [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	0
Equity Securities [Member] | Public Utility, Equities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	64,324	105,485
Equity Securities [Member] | Public Utility, Equities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	64,324	105,485
Equity Securities [Member] | Public Utility, Equities [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0
Equity Securities [Member] | Public Utility, Equities [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0
Equity Securities [Member] | Banks, Trust and Insurance, Equities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	11,700	9,757
Equity Securities [Member] | Banks, Trust and Insurance, Equities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	11,700	9,757
Equity Securities [Member] | Banks, Trust and Insurance, Equities [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0
Equity Securities [Member] | Banks, Trust and Insurance, Equities [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0
Equity Securities [Member] | Industrial, Miscellaneous, and All Others [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	186,172	257,356
Equity Securities [Member] | Industrial, Miscellaneous, and All Others [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	186,172	257,356
Equity Securities [Member] | Industrial, Miscellaneous, and All Others [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0
Equity Securities [Member] | Industrial, Miscellaneous, and All Others [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0
Equity Securities [Member] | Nonredeemable Preferred Stock [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	24,795	28,563
Equity Securities [Member] | Nonredeemable Preferred Stock [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0
Equity Securities [Member] | Nonredeemable Preferred Stock [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	24,795	28,563
Equity Securities [Member] | Nonredeemable Preferred Stock [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0
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	11,696	11,719
Equity Securities [Member] | Partnership Interest In Private Credit Fund [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0
Equity Securities [Member] | Partnership Interest In Private Credit Fund [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	0	0
Equity Securities [Member] | Partnership Interest In Private Credit Fund [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	11,696	11,719
Short-term Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	62,001	88,361
Short-term Investments [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	59,996	69,999
Short-term Investments [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	2,005	18,362
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	100,834	284,181
Money Market Funds [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure, Recurring	100,834	284,181
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
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	6,059	4,025
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	6,059	4,025
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	266	194
Equity Contract [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities, Fair Value Disclosure, Recurring	266	194
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
Secured Debt [Member] | 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