Investments (Summary Of Aggregate Market Value And Gross Unrealized Depreciation Of Fixed Maturity And Equity Securities, By Security Type) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Less than 12 months, Market Value	$ 1,925,177	$ 1,237,220
Available for sale securities, Less than 12 months, Gross Unrealized Depreciation	(62,697)	(72,254)
Available for sale securities, Greater than 12 months, Market Value	645,829	654,926
Available for sale securities, Greater than 12 months, Gross Unrealized Depreciation	(37,635)	(18,204)
Available-for-sale Securities, Market Value, Total	2,571,006	1,892,146
Available-for-sale Securities, Gross Unrealized Depreciation, Total	(100,332)	(90,458)
Fixed Maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Less than 12 months, Market Value	1,925,177	1,237,220
Available for sale securities, Less than 12 months, Gross Unrealized Depreciation	(62,697)	(72,254)
Available for sale securities, Greater than 12 months, Market Value	645,829	654,926
Available for sale securities, Greater than 12 months, Gross Unrealized Depreciation	(37,635)	(18,204)
Available-for-sale Securities, Market Value, Total	2,571,006	1,892,146
Available-for-sale Securities, Gross Unrealized Depreciation, Total	(100,332)	(90,458)
U.S. Treasury Securities And Obligations Of U.S. Government Agencies And Corporations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Less than 12 months, Market Value	216,352	13,187
Available for sale securities, Less than 12 months, Gross Unrealized Depreciation	(712)	(20)
Available for sale securities, Greater than 12 months, Market Value	692	26,897
Available for sale securities, Greater than 12 months, Gross Unrealized Depreciation	(6)	(284)
Available-for-sale Securities, Market Value, Total	217,044	40,084
Available-for-sale Securities, Gross Unrealized Depreciation, Total	(718)	(304)
Obligations of US States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Less than 12 months, Market Value	6,434	20,428
Available for sale securities, Less than 12 months, Gross Unrealized Depreciation	(84)	(242)
Available for sale securities, Greater than 12 months, Market Value	4,917	18,199
Available for sale securities, Greater than 12 months, Gross Unrealized Depreciation	(806)	(384)
Available-for-sale Securities, Market Value, Total	11,351	38,627
Available-for-sale Securities, Gross Unrealized Depreciation, Total	(890)	(626)
Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Less than 12 months, Market Value	866,715	830,928
Available for sale securities, Less than 12 months, Gross Unrealized Depreciation	(49,034)	(48,891)
Available for sale securities, Greater than 12 months, Market Value	307,215	171,207
Available for sale securities, Greater than 12 months, Gross Unrealized Depreciation	(21,691)	(4,328)
Available-for-sale Securities, Market Value, Total	1,173,930	1,002,135
Available-for-sale Securities, Gross Unrealized Depreciation, Total	(70,725)	(53,219)
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Less than 12 months, Market Value	102,506	62,451
Available for sale securities, Less than 12 months, Gross Unrealized Depreciation	(791)	$ (374)
Available for sale securities, Greater than 12 months, Market Value	28,048
Available for sale securities, Greater than 12 months, Gross Unrealized Depreciation	(272)
Available-for-sale Securities, Market Value, Total	130,554	$ 62,451
Available-for-sale Securities, Gross Unrealized Depreciation, Total	(1,063)	(374)
Commercial Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Less than 12 months, Market Value	26,483	11,742
Available for sale securities, Less than 12 months, Gross Unrealized Depreciation	(511)	$ (51)
Available for sale securities, Greater than 12 months, Market Value
Available for sale securities, Greater than 12 months, Gross Unrealized Depreciation
Available-for-sale Securities, Market Value, Total	26,483	$ 11,742
Available-for-sale Securities, Gross Unrealized Depreciation, Total	(511)	(51)
Agency Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Less than 12 months, Market Value	320,285	24,230
Available for sale securities, Less than 12 months, Gross Unrealized Depreciation	(3,094)	(59)
Available for sale securities, Greater than 12 months, Market Value	150,095	267,824
Available for sale securities, Greater than 12 months, Gross Unrealized Depreciation	(3,509)	(4,661)
Available-for-sale Securities, Market Value, Total	470,380	292,054
Available-for-sale Securities, Gross Unrealized Depreciation, Total	(6,603)	(4,720)
Foreign Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Less than 12 months, Market Value	61,498	45,521
Available for sale securities, Less than 12 months, Gross Unrealized Depreciation	(2,182)	(913)
Available for sale securities, Greater than 12 months, Market Value	77,911	53,086
Available for sale securities, Greater than 12 months, Gross Unrealized Depreciation	(6,243)	(4,431)
Available-for-sale Securities, Market Value, Total	139,409	98,607
Available-for-sale Securities, Gross Unrealized Depreciation, Total	(8,425)	(5,344)
Foreign Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Less than 12 months, Market Value	324,904	228,733
Available for sale securities, Less than 12 months, Gross Unrealized Depreciation	(6,289)	(21,704)
Available for sale securities, Greater than 12 months, Market Value	76,951	117,713
Available for sale securities, Greater than 12 months, Gross Unrealized Depreciation	(5,108)	(4,116)
Available-for-sale Securities, Market Value, Total	401,855	346,446
Available-for-sale Securities, Gross Unrealized Depreciation, Total	$ (11,397)	$ (25,820)