Fair Value (Fair Value Measurement Levels For All Assets, Recorded At Fair And Market Value)(Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	$ 5,384,362	$ 5,293,411
Fixed maturities - available for sale, at fair value		1,509
Equity securities - available for sale, at market value		16
Equity securities - available for sale, at fair value	1,199,347	1,299,037
Other invested assets, at fair value	1,684,860	1,655,311
Quoted Prices in Active Markets For Identical Assets Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities - available for sale, at market value		16
Equity securities - available for sale, at fair value	1,109,801	1,188,613
Other invested assets, at fair value	1,684,860	1,655,311
Significant Other Observable Inputs Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	5,372,962	5,277,648
Fixed maturities - available for sale, at fair value		1,509
Equity securities - available for sale, at fair value	89,546	110,424
Significant Unobservable Inputs Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	11,400	15,763
U.S. Treasury Securities And Obligations Of U.S. Government Agencies And Corporations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	227,444	136,836
U.S. Treasury Securities And Obligations Of U.S. Government Agencies And Corporations [Member] | Significant Other Observable Inputs Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	227,444	136,836
Obligations of US States and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	714,279	824,472
Obligations of US States and Political Subdivisions [Member] | Significant Other Observable Inputs Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	714,279	824,472
Corporate Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	1,999,162	1,978,935
Corporate Debt Securities [Member] | Significant Other Observable Inputs Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	1,993,887	1,978,935
Corporate Debt Securities [Member] | Significant Unobservable Inputs Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	5,275
Asset-backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	132,461	94,823
Asset-backed Securities [Member] | Significant Other Observable Inputs Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	132,461	94,823
Commercial Mortgage-Backed Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	64,521	59,268
Commercial Mortgage-Backed Securities [Member] | Significant Other Observable Inputs Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	64,521	50,671
Commercial Mortgage-Backed Securities [Member] | Significant Unobservable Inputs Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value		8,597
Agency Residential [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	726,035	598,117
Agency Residential [Member] | Significant Other Observable Inputs Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	726,035	598,117
Non-agency Residential [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	168	315
Non-agency Residential [Member] | Significant Other Observable Inputs Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	168	315
Foreign Government Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	464,707	537,087
Foreign Government Debt Securities [Member] | Significant Other Observable Inputs Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	464,707	537,087
Foreign Corporate Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	1,055,585	1,063,558
Foreign Corporate Debt Securities [Member] | Significant Other Observable Inputs Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	1,049,460	1,056,392
Foreign Corporate Debt Securities [Member] | Significant Unobservable Inputs Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fixed maturity securities - available for sale, at market value	$ 6,125	$ 7,166