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	Jun. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	$ 488,789	$ 2,030,690
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(36,952)	(76,054)
Available-for-sale securities, estimated fair value, 12 months or longer	367,263	813,147
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(6,569)	(19,842)
Available-for-sale securities, estimated fair value	856,052	2,843,837
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(43,521)	(95,896)
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	7,537	427,003
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(7)	(3,648)
Available-for-sale securities, estimated fair value, 12 months or longer	8,529	92,552
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(2)	(1,133)
Available-for-sale securities, estimated fair value	16,066	519,555
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(9)	(4,781)
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	2,789	169,362
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(2)	(4,864)
Available-for-sale securities, estimated fair value, 12 months or longer	47,301	70,101
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(2,327)	(3,361)
Available-for-sale securities, estimated fair value	50,090	239,463
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(2,329)	(8,225)
Foreign Governments [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	42,255	51,328
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(304)	(249)
Available-for-sale securities, estimated fair value, 12 months or longer	5,026	40,345
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(1)	(1,432)
Available-for-sale securities, estimated fair value	47,281	91,673
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(305)	(1,681)
Commercial Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	23,518	289,058
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(142)	(3,600)
Available-for-sale securities, estimated fair value, 12 months or longer	63,738	95,843
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(391)	(1,399)
Available-for-sale securities, estimated fair value	87,256	384,901
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(533)	(4,999)
Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	6,584	78,814
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(2,304)	(2,858)
Available-for-sale securities, estimated fair value, 12 months or longer	104,340	137,100
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(483)	(3,422)
Available-for-sale securities, estimated fair value	110,924	215,914
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(2,787)	(6,280)
Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	0	6,228
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	0	(54)
Available-for-sale securities, estimated fair value, 12 months or longer	6,316	24,315
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(17)	(352)
Available-for-sale securities, estimated fair value	6,316	30,543
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(17)	(406)
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	37,222	470,694
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(1,664)	(9,509)
Available-for-sale securities, estimated fair value, 12 months or longer	104,194	343,737
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(1,282)	(8,324)
Available-for-sale securities, estimated fair value	141,416	814,431
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(2,946)	(17,833)
Total Fixed Maturities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	119,905	1,492,487
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(4,423)	(24,782)
Available-for-sale securities, estimated fair value, 12 months or longer	339,444	803,993
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(4,503)	(19,423)
Available-for-sale securities, estimated fair value	459,349	2,296,480
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(8,926)	(44,205)
Insurance, Banks And Other Financial Institutions [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	77,737	63,873
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(12,641)	(6,384)
Available-for-sale securities, estimated fair value, 12 months or longer	0	6,247
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	0	(167)
Available-for-sale securities, estimated fair value	77,737	70,120
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(12,641)	(6,551)
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	191,170	344,857
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(19,887)	(44,879)
Available-for-sale securities, estimated fair value, 12 months or longer	27,819	2,907
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(2,066)	(252)
Available-for-sale securities, estimated fair value	218,989	347,764
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(21,953)	(45,131)
Total Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	268,907	408,730
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(32,528)	(51,263)
Available-for-sale securities, estimated fair value, 12 months or longer	27,819	9,154
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(2,066)	(419)
Available-for-sale securities, estimated fair value	296,726	417,884
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(34,594)	(51,682)
Short-Term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	99,977	129,473
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(1)	(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	99,977	129,473
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	$ (1)	$ (9)