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, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Less than 12 months, Market Value	$ 836,311	$ 4,928,451
Fixed maturity securities, Duration of Unrealized loss, less than 12 months, Gross Unrealized Depreciation	(32,838)	(139,624)
Fixed maturity securities, Greater than 12 months, Market Value	1,286,850	1,443,732
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(96,525)	(133,068)
Fixed maturity securities, Total, Market Value	2,123,161	6,372,183
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(129,363)	(272,692)
Fixed Maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Less than 12 months, Market Value	836,311	4,928,451
Fixed maturity securities, Duration of Unrealized loss, less than 12 months, Gross Unrealized Depreciation	(32,838)	(139,624)
Fixed maturity securities, Greater than 12 months, Market Value	1,186,315	1,351,825
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(86,089)	(116,336)
Fixed maturity securities, Total, Market Value	2,022,626	6,280,276
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(118,927)	(255,960)
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	7,851	539,177
Fixed maturity securities, Duration of Unrealized loss, less than 12 months, Gross Unrealized Depreciation	(161)	(1,855)
Fixed maturity securities, Greater than 12 months, Market Value		692
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation		(6)
Fixed maturity securities, Total, Market Value	7,851	539,869
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(161)	(1,861)
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		6,434
Fixed maturity securities, Duration of Unrealized loss, less than 12 months, Gross Unrealized Depreciation		(84)
Fixed maturity securities, Greater than 12 months, Market Value	562	4,917
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(478)	(806)
Fixed maturity securities, Total, Market Value	562	11,351
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(478)	(890)
Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Less than 12 months, Market Value	361,829	1,818,331
Fixed maturity securities, Duration of Unrealized loss, less than 12 months, Gross Unrealized Depreciation	(7,778)	(74,161)
Fixed maturity securities, Greater than 12 months, Market Value	403,815	440,682
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(23,692)	(35,149)
Fixed maturity securities, Total, Market Value	765,644	2,259,013
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(31,470)	(109,310)
Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Less than 12 months, Market Value	23,269	348,545
Fixed maturity securities, Duration of Unrealized loss, less than 12 months, Gross Unrealized Depreciation	(76)	(2,510)
Fixed maturity securities, Greater than 12 months, Market Value	64,821	67,230
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(784)	(1,303)
Fixed maturity securities, Total, Market Value	88,090	415,775
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(860)	(3,813)
Commercial Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Less than 12 months, Market Value	19,532	145,490
Fixed maturity securities, Duration of Unrealized loss, less than 12 months, Gross Unrealized Depreciation	(1,727)	(3,375)
Fixed maturity securities, Greater than 12 months, Market Value	5,823
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(342)
Fixed maturity securities, Total, Market Value	25,355	145,490
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(2,069)	(3,375)
Agency Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Less than 12 months, Market Value	101,296	1,021,390
Fixed maturity securities, Duration of Unrealized loss, less than 12 months, Gross Unrealized Depreciation	(467)	(10,014)
Fixed maturity securities, Greater than 12 months, Market Value	203,950	326,449
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(1,186)	(8,045)
Fixed maturity securities, Total, Market Value	305,246	1,347,839
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(1,653)	(18,059)
Non-Agency Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Less than 12 months, Market Value		152
Fixed maturity securities, Duration of Unrealized loss, less than 12 months, Gross Unrealized Depreciation		(2)
Fixed maturity securities, Greater than 12 months, Market Value	146	38
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(46)	(44)
Fixed maturity securities, Total, Market Value	146	190
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(46)	(46)
Foreign Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Less than 12 months, Market Value	128,397	227,384
Fixed maturity securities, Duration of Unrealized loss, less than 12 months, Gross Unrealized Depreciation	(11,750)	(21,996)
Fixed maturity securities, Greater than 12 months, Market Value	210,746	216,428
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(27,707)	(30,209)
Fixed maturity securities, Total, Market Value	339,143	443,812
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(39,457)	(52,205)
Foreign Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Less than 12 months, Market Value	194,137	821,548
Fixed maturity securities, Duration of Unrealized loss, less than 12 months, Gross Unrealized Depreciation	(10,879)	(25,627)
Fixed maturity securities, Greater than 12 months, Market Value	296,452	295,389
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(31,854)	(40,774)
Fixed maturity securities, Total, Market Value	490,589	1,116,937
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(42,733)	(66,401)
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Greater than 12 months, Market Value	100,535	91,907
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(10,436)	(16,732)
Fixed maturity securities, Total, Market Value	100,535	91,907
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	$ (10,436)	$ (16,732)