Investments (Summary Of Aggregate Market Value And Gross Unrealized Depreciation Of Fixed Maturity And Equity Securities, By Contractual Maturity) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Market Value	$ 1,756,495	$ 4,928,451
Fixed maturity securities, Duration of Unrealized loss, less than 12 months, Gross Unrealized Depreciation	(67,675)	(139,624)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	1,292,635	1,443,732
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(106,687)	(133,068)
Fixed maturity securities, Total, Market Value	3,049,130	6,372,183
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(174,362)	(272,692)
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	1,756,495	4,928,451
Fixed maturity securities, Duration of Unrealized loss, less than 12 months, Gross Unrealized Depreciation	(67,675)	(139,624)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	1,195,864	1,351,825
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(93,713)	(116,336)
Fixed maturity securities, Total, Market Value	2,952,359	6,280,276
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(161,388)	(255,960)
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	50,743	29,737
Fixed maturity securities, Duration of Unrealized loss, less than 12 months, Gross Unrealized Depreciation	(255)	(1,840)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	91,385	74,615
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(14,690)	(13,440)
Fixed maturity securities, Total, Market Value	142,128	104,352
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(14,945)	(15,280)
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	843,152	2,328,805
Fixed maturity securities, Duration of Unrealized loss, less than 12 months, Gross Unrealized Depreciation	(37,957)	(62,329)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	550,261	651,228
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(46,326)	(59,993)
Fixed maturity securities, Total, Market Value	1,393,413	2,980,033
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(84,283)	(122,322)
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	467,988	969,139
Fixed maturity securities, Duration of Unrealized loss, less than 12 months, Gross Unrealized Depreciation	(21,816)	(52,725)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	162,567	206,538
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(24,926)	(28,018)
Fixed maturity securities, Total, Market Value	630,555	1,175,677
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(46,742)	(80,743)
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	54,061	85,193
Fixed maturity securities, Duration of Unrealized loss, less than 12 months, Gross Unrealized Depreciation	(3,955)	(6,829)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	25,598	25,727
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(3,761)	(5,493)
Fixed maturity securities, Total, Market Value	79,659	110,920
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(7,716)	(12,322)
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	66,629	348,545
Fixed maturity securities, Duration of Unrealized loss, less than 12 months, Gross Unrealized Depreciation	(257)	(2,510)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	68,896	67,230
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(1,197)	(1,303)
Fixed maturity securities, Total, Market Value	135,525	415,775
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	(1,454)	(3,813)
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	273,922	1,167,032
Fixed maturity securities, Duration of Unrealized loss, less than 12 months, Gross Unrealized Depreciation	(3,435)	(13,391)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	297,157	326,487
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(2,813)	(8,089)
Fixed maturity securities, Total, Market Value	571,079	1,493,519
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation, Total	$ (6,248)	$ (21,480)