Investments (Summary Of Aggregate Market Value And Gross Unrealized Depreciation Of Fixed Maturity And Equity Securities, By Contractual Maturity) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, 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, Duration of Unrealized Loss, 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, Duration of Unrealized Loss, 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, Duration of Unrealized Loss, 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)
Due In One Year Or Less [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Market Value	87,985	98,021
Fixed maturity securities, duration of unrealized loss, less than 12 months, gross unrealized depreciation	(7,088)	(5,166)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	49,702	80,002
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(9,253)	(8,174)
Fixed maturity securities, Total, Market Value	137,687	178,023
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(16,341)	(13,340)
Due In One Year Through Five Years [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Market Value	1,476,198	1,233,244
Fixed maturity securities, duration of unrealized loss, less than 12 months, gross unrealized depreciation	(45,857)	(68,124)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	332,321	518,613
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(11,722)	(12,761)
Fixed maturity securities, Total, Market Value	1,808,519	1,751,857
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(57,579)	(80,885)
Due In Five Years Through Ten Years [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Market Value	887,119	679,374
Fixed maturity securities, duration of unrealized loss, less than 12 months, gross unrealized depreciation	(28,977)	(28,529)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	136,078	187,717
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(7,596)	(10,734)
Fixed maturity securities, Total, Market Value	1,023,197	867,091
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(36,573)	(39,263)
Due After Ten Years [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Market Value	173,221	72,436
Fixed maturity securities, duration of unrealized loss, less than 12 months, gross unrealized depreciation	(5,316)	(6,172)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	40,718	50,518
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(3,941)	(4,116)
Fixed maturity securities, Total, Market Value	213,939	122,954
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(9,257)	(10,288)
Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, 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, Duration of Unrealized Loss, 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)
Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Market Value	552,459	169,998
Fixed maturity securities, duration of unrealized loss, less than 12 months, gross unrealized depreciation	(4,612)	(295)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	417,779	689,015
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(7,257)	(11,764)
Fixed maturity securities, Total, Market Value	970,238	859,013
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	$ (11,869)	$ (12,059)