Investments (Summary Of Aggregate Market Value And Gross Unrealized Depreciation Of Fixed Maturity And Equity Securities, By Contractual Maturity) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Market Value	$ 2,967,975	$ 3,637,310
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(61,127)	(123,833)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	1,202,112	639,825
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(56,334)	(40,762)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	4,170,087	4,277,135
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation	(117,461)	(164,595)
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	182,786	143,098
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(5,312)	(3,503)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	46,643	46,691
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(5,320)	(5,330)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	229,429	189,789
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation	(10,632)	(8,833)
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	1,331,340	1,125,680
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(23,562)	(25,365)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	288,624	204,779
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(12,169)	(11,279)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	1,619,964	1,330,459
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation	(35,731)	(36,644)
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	740,585	810,969
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(18,467)	(35,169)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	124,208	48,064
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(7,167)	(3,844)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	864,793	859,033
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation	(25,634)	(39,013)
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	91,660	329,415
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(3,518)	(19,348)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	122,417	61,629
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(9,735)	(8,927)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	214,077	391,044
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation	(13,253)	(28,275)
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	22,658	5,494
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(128)	(6)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	119	1,128
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(86)	(416)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	22,777	6,622
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation	(214)	(422)
Non-Agency Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Market Value	598,946	1,222,654
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(10,140)	(40,442)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	620,101	277,534
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(21,857)	(10,966)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	1,219,047	1,500,188
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation	$ (31,997)	$ (51,408)