Investments (Summary Of Gross Unrealized Investment Losses By Length Of Time That Securities Have Continuously Been In An Unrealized Loss Position) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Estimated Fair Value, Less than 12 months	$ 221,090	$ 542,101
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses, Less than 12 months	(10,607)	(15,315)
Available-for-sale securities, Estimated Fair Value, 12 months or longer	22,196	45,786
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses, 12 months or longer	(842)	(2,355)
Available-for-sale securities, Estimated Fair Value	243,286	587,887
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses	(11,449)	(17,670)
U.S. Treasury securities and obligations Of U.S. government agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Estimated Fair Value, Less than 12 months	78,023	32,384
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses, Less than 12 months	(222)	(9)
Available-for-sale securities, Estimated Fair Value, 12 months or longer	0	0
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses, 12 months or longer	0	0
Available-for-sale securities, Estimated Fair Value	78,023	32,384
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses	(222)	(9)
Obligations of states, municipalities and political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Estimated Fair Value, Less than 12 months	12,592	1,016
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses, Less than 12 months	(240)	(2)
Available-for-sale securities, Estimated Fair Value, 12 months or longer	16,189	17,261
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses, 12 months or longer	(684)	(792)
Available-for-sale securities, Estimated Fair Value	28,781	18,277
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses	(924)	(794)
Foreign governments [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Estimated Fair Value, Less than 12 months	35,520	40,340
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses, Less than 12 months	(331)	(1,068)
Available-for-sale securities, Estimated Fair Value, 12 months or longer	0	0
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses, 12 months or longer	0	0
Available-for-sale securities, Estimated Fair Value	35,520	40,340
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses	(331)	(1,068)
Residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Estimated Fair Value, Less than 12 months	551	489
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses, Less than 12 months	(2,263)	(2,263)
Available-for-sale securities, Estimated Fair Value, 12 months or longer	0	2,045
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses, 12 months or longer	0	(13)
Available-for-sale securities, Estimated Fair Value	551	2,534
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses	(2,263)	(2,276)
Asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Estimated Fair Value, Less than 12 months	0	0
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses, Less than 12 months	0	0
Available-for-sale securities, Estimated Fair Value, 12 months or longer	0	32
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses, 12 months or longer	0	(9)
Available-for-sale securities, Estimated Fair Value	0	32
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses	0	(9)
All other corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Estimated Fair Value, Less than 12 months	15,137	74,812
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses, Less than 12 months	(6,954)	(7,829)
Available-for-sale securities, Estimated Fair Value, 12 months or longer	5,908	7,923
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses, 12 months or longer	(147)	(1,535)
Available-for-sale securities, Estimated Fair Value	21,045	82,735
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses	(7,101)	(9,364)
Total fixed maturities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Estimated Fair Value, Less than 12 months	141,823	149,041
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses, Less than 12 months	(10,010)	(11,171)
Available-for-sale securities, Estimated Fair Value, 12 months or longer	22,097	27,261
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses, 12 months or longer	(831)	(2,349)
Available-for-sale securities, Estimated Fair Value	163,920	176,302
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses	(10,841)	(13,520)
Insurance companies, banks and trusts [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Estimated Fair Value, Less than 12 months	0	26,514
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses, Less than 12 months	0	(1,366)
Available-for-sale securities, Estimated Fair Value, 12 months or longer	0	0
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses, 12 months or longer	0	0
Available-for-sale securities, Estimated Fair Value	0	26,514
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses	0	(1,366)
Industrial, consumer and all other [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Estimated Fair Value, Less than 12 months	32,272	70,555
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses, Less than 12 months	(590)	(2,774)
Available-for-sale securities, Estimated Fair Value, 12 months or longer	99	18,525
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses, 12 months or longer	(11)	(6)
Available-for-sale securities, Estimated Fair Value	32,371	89,080
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses	(601)	(2,780)
Total equity securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Estimated Fair Value, Less than 12 months	32,272	97,069
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses, Less than 12 months	(590)	(4,140)
Available-for-sale securities, Estimated Fair Value, 12 months or longer	99	18,525
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses, 12 months or longer	(11)	(6)
Available-for-sale securities, Estimated Fair Value	32,371	115,594
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses	(601)	(4,146)
Short-term investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Estimated Fair Value, Less than 12 months	46,995	295,991
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses, Less than 12 months	(7)	(4)
Available-for-sale securities, Estimated Fair Value, 12 months or longer	0	0
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses, 12 months or longer	0	0
Available-for-sale securities, Estimated Fair Value	46,995	295,991
Available-for-sale securities, Gross Unrealized Holding and Other-Than-Temporary Impairment Losses	$ (7)	$ (4)