Investments (Summary Of Aggregate Market Value And Gross Unrealized Depreciation Of Fixed Maturity And Equity Securities, By Security Type) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Less than 12 months, Market Value	$ 3,392,993	$ 2,495,611
Fixed maturity securities, duration of unrealized loss, less than 12 months, gross unrealized depreciation	(98,486)	(113,584)
Fixed maturity securities, Greater than 12 months, Market Value	1,052,987	1,599,859
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(48,030)	(55,428)
Fixed maturity securities, Total, Market Value	4,445,980	4,095,470
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(146,516)	(169,012)
Fixed Maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Less than 12 months, Market Value	3,337,718	2,445,326
Fixed maturity securities, duration of unrealized loss, less than 12 months, gross unrealized depreciation	(93,415)	(109,516)
Fixed maturity securities, Greater than 12 months, Market Value	980,897	1,525,865
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(39,783)	(47,549)
Fixed maturity securities, Total, Market Value	4,318,615	3,971,191
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(133,198)	(157,065)
U.S. Treasury Securities And Obligations Of U.S. Government Agencies And Corporations [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Less than 12 months, Market Value	25,004	13,187
Fixed maturity securities, duration of unrealized loss, less than 12 months, gross unrealized depreciation	(335)	(20)
Fixed maturity securities, Greater than 12 months, Market Value	1,969	26,897
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(129)	(284)
Fixed maturity securities, Total, Market Value	26,973	40,084
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(464)	(304)
Obligations Of U.S. States And Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Less than 12 months, Market Value	97,850	20,428
Fixed maturity securities, duration of unrealized loss, less than 12 months, gross unrealized depreciation	(2,141)	(242)
Fixed maturity securities, Greater than 12 months, Market Value	17,686	18,199
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(744)	(384)
Fixed maturity securities, Total, Market Value	115,536	38,627
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(2,885)	(626)
Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Less than 12 months, Market Value	1,407,353	1,245,830
Fixed maturity securities, duration of unrealized loss, less than 12 months, gross unrealized depreciation	(24,960)	(55,388)
Fixed maturity securities, Greater than 12 months, Market Value	282,817	362,320
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(8,032)	(7,518)
Fixed maturity securities, Total, Market Value	1,690,170	1,608,150
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(32,992)	(62,906)
Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Less than 12 months, Market Value	160,736	192,253
Fixed maturity securities, duration of unrealized loss, less than 12 months, gross unrealized depreciation	(1,565)	(1,230)
Fixed maturity securities, Greater than 12 months, Market Value	4,299
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(14)
Fixed maturity securities, Total, Market Value	165,035	192,253
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(1,579)	(1,230)
Commercial Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Less than 12 months, Market Value	133,162	28,191
Fixed maturity securities, duration of unrealized loss, less than 12 months, gross unrealized depreciation	(1,798)	(123)
Fixed maturity securities, Greater than 12 months, Market Value		9,777
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation		(306)
Fixed maturity securities, Total, Market Value	133,162	37,968
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(1,798)	(429)
Agency Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Less than 12 months, Market Value	419,093	141,807
Fixed maturity securities, duration of unrealized loss, less than 12 months, gross unrealized depreciation	(2,812)	(172)
Fixed maturity securities, Greater than 12 months, Market Value	417,728	678,972
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(7,214)	(11,401)
Fixed maturity securities, Total, Market Value	836,821	820,779
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(10,026)	(11,573)
Non-Agency Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Less than 12 months, Market Value	204
Fixed maturity securities, duration of unrealized loss, less than 12 months, gross unrealized depreciation	(2)
Fixed maturity securities, Greater than 12 months, Market Value	51	266
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(43)	(57)
Fixed maturity securities, Total, Market Value	255	266
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(45)	(57)
Foreign Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Less than 12 months, Market Value	337,577	235,725
Fixed maturity securities, duration of unrealized loss, less than 12 months, gross unrealized depreciation	(20,816)	(15,415)
Fixed maturity securities, Greater than 12 months, Market Value	98,995	139,200
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(12,332)	(11,451)
Fixed maturity securities, Total, Market Value	436,572	374,925
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(33,148)	(26,866)
Foreign Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Less than 12 months, Market Value	756,739	567,905
Fixed maturity securities, duration of unrealized loss, less than 12 months, gross unrealized depreciation	(38,986)	(36,926)
Fixed maturity securities, Greater than 12 months, Market Value	157,352	290,234
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(11,275)	(16,148)
Fixed maturity securities, Total, Market Value	914,091	858,139
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(50,261)	(53,074)
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Less than 12 months, Market Value	55,275	50,285
Fixed maturity securities, duration of unrealized loss, less than 12 months, gross unrealized depreciation	(5,071)	(4,068)
Fixed maturity securities, Greater than 12 months, Market Value	72,090	73,994
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(8,247)	(7,879)
Fixed maturity securities, Total, Market Value	127,365	124,279
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	$ (13,318)	$ (11,947)