Investments (Summary Of Aggregate Market Value And Gross Unrealized Depreciation Of Fixed Maturity And Equity Securities By Security Type) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Less than 12 months, Market Value	$ 1,224,521	$ 1,588,439
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Greater than 12 months, Market Value	865,881	830,082
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Total, Market Value	2,090,402	2,418,521
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(40,932)	(36,827)
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(60,555)	(79,056)
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation	(101,487)	(115,883)
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Less than 12 months, Market Value	108,939	273,378
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Greater than 12 months, Market Value	204,466	13
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Total, Market Value	313,405	273,391
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(8,499)	(2,584)
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(10,251)	(2)
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation	(18,750)	(2,586)
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 - available for sale, Duration of Unrealized Loss, Less than 12 months, Market Value		70,193
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Greater than 12 months, Market Value	3,452	43,264
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Total, Market Value	3,452	113,457
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation		(2,425)
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(287)	(3,230)
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation	(287)	(5,655)
Obligations Of U.S. States And Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Less than 12 months, Market Value		336,522
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Greater than 12 months, Market Value	7,518	171,812
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Total, Market Value	7,518	508,334
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation		(9,520)
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(525)	(15,409)
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation	(525)	(24,929)
Foreign Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Less than 12 months, Market Value	39,534	194,113
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Greater than 12 months, Market Value	132,977	203,913
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Total, Market Value	172,511	398,026
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(1,035)	(6,416)
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(7,354)	(19,252)
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation	(8,389)	(25,668)
Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Less than 12 months, Market Value	512,255	186,898
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Greater than 12 months, Market Value	120,064	107,520
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Total, Market Value	632,319	294,418
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(14,962)	(5,077)
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(12,092)	(11,441)
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation	(27,054)	(16,518)
Foreign Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Less than 12 months, Market Value	278,949	309,627
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Greater than 12 months, Market Value	259,641	198,161
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Total, Market Value	538,590	507,788
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(12,287)	(9,452)
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(19,902)	(22,214)
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation	(32,189)	(31,666)
Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Less than 12 months, Market Value	20,839	7,816
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Greater than 12 months, Market Value	3,655	2,408
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Total, Market Value	24,494	10,224
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(339)	(92)
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(211)	(123)
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation	(550)	(215)
Fixed Maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Less than 12 months, Market Value	1,115,582	1,315,061
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Greater than 12 months, Market Value	661,415	830,069
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Total, Market Value	1,776,997	2,145,130
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(32,433)	(34,243)
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(50,304)	(79,054)
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation	(82,737)	(113,297)
Non-Agency Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Less than 12 months, Market Value	1,542
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Greater than 12 months, Market Value	35,679	44,341
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Total, Market Value	37,221	44,341
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(19)
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(756)	(1,723)
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation	(775)	(1,723)
Agency Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Less than 12 months, Market Value	253,171	208,930
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Greater than 12 months, Market Value	43,894	614
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Total, Market Value	297,065	209,544
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(2,524)	(1,236)
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(542)	(233)
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation	(3,066)	(1,469)
Commercial Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Less than 12 months, Market Value	9,292	962
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Greater than 12 months, Market Value	54,535	58,036
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Total, Market Value	63,827	58,998
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(1,267)	(25)
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Greater than 12 months, Gross Unrealized Depreciation	(8,635)	(5,429)
Fixed maturity securities - available for sale, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation	$ (9,902)	$ (5,454)