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	Dec. 31, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	$ (32,433)	$ (34,243)
Fixed maturity securities, duration of unrealized loss, Greater than 12 months, Gross Unrealized Depreciation	(50,304)	(79,054)
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	1,115,582	1,315,061
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(32,433)	(34,243)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	661,415	830,069
Fixed maturity securities, duration of unrealized loss, Greater than 12 months, Gross Unrealized Depreciation	(50,304)	(79,054)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	1,776,997	2,145,130
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation	(82,737)	(113,297)
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	264,005	209,892
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(3,810)	(1,261)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	134,108	102,991
Fixed maturity securities, duration of unrealized loss, Greater than 12 months, Gross Unrealized Depreciation	(9,933)	(7,385)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	398,113	312,883
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation	(13,743)	(8,646)
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	20,839	7,816
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(339)	(92)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	3,655	2,408
Fixed maturity securities, duration of unrealized loss, Greater than 12 months, Gross Unrealized Depreciation	(211)	(123)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	24,494	10,224
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation	(550)	(215)
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	44,930	400,852
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(2,938)	(11,073)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	35,395	300,432
Fixed maturity securities, duration of unrealized loss, Greater than 12 months, Gross Unrealized Depreciation	(7,308)	(30,176)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	80,325	701,284
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation	(10,246)	(41,249)
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	337,232	358,468
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(13,019)	(9,538)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	159,476	144,264
Fixed maturity securities, duration of unrealized loss, Greater than 12 months, Gross Unrealized Depreciation	(8,264)	(12,624)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	496,708	502,732
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation	(21,283)	(22,162)
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	421,995	313,179
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(12,001)	(11,829)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	256,698	224,770
Fixed maturity securities, duration of unrealized loss, Greater than 12 months, Gross Unrealized Depreciation	(15,635)	(19,685)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	678,693	537,949
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation	(27,636)	(31,514)
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	26,581	24,854
Fixed maturity securities, Duration of Unrealized Loss, Less than 12 months, Gross Unrealized Depreciation	(326)	(450)
Fixed maturity securities, Duration of Unrealized Loss, Greater than 12 months, Market Value	72,083	55,204
Fixed maturity securities, duration of unrealized loss, Greater than 12 months, Gross Unrealized Depreciation	(8,953)	(9,061)
Fixed maturity securities, Duration of Unrealized Loss, Total, Market Value	98,664	80,058
Fixed maturity securities, Duration of Unrealized Loss, Total, Gross Unrealized Depreciation	$ (9,279)	$ (9,511)