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	Jun. 30, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	$ 531,390	$ 4,827,824
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(6,925)	(211,358)
Available-for-sale securities, estimated fair value, 12 months or longer	1,919,820	31,247
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(43,551)	(546)
Available-for-sale securities, estimated fair value	2,451,210	4,859,071
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(50,476)	(211,904)
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	30,804	587,929
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(27)	(30,342)
Available-for-sale securities, estimated fair value, 12 months or longer	223,178	0
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(6,498)	0
Available-for-sale securities, estimated fair value	253,982	587,929
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(6,525)	(30,342)
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	19,254	513,608
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(172)	(27,238)
Available-for-sale securities, estimated fair value, 12 months or longer	191,416	3,512
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(7,958)	(146)
Available-for-sale securities, estimated fair value	210,670	517,120
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(8,130)	(27,384)
Foreign Governments [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	38,376	950,040
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(252)	(54,411)
Available-for-sale securities, estimated fair value, 12 months or longer	213,586	0
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(2,994)	0
Available-for-sale securities, estimated fair value	251,962	950,040
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(3,246)	(54,411)
Commercial Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	10,164	357,737
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(22)	(11,796)
Available-for-sale securities, estimated fair value, 12 months or longer	168,395	0
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(2,468)	0
Available-for-sale securities, estimated fair value	178,559	357,737
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(2,490)	(11,796)
Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	40,190	437,675
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(2,417)	(18,700)
Available-for-sale securities, estimated fair value, 12 months or longer	272,115	0
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(6,797)	0
Available-for-sale securities, estimated fair value	312,305	437,675
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(9,214)	(18,700)
Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	6,779	142,011
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(70)	(1,614)
Available-for-sale securities, estimated fair value, 12 months or longer	56,014	0
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(833)	0
Available-for-sale securities, estimated fair value	62,793	142,011
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(903)	(1,614)
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	30,233	1,817,737
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(2,410)	(66,539)
Available-for-sale securities, estimated fair value, 12 months or longer	795,116	0
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(16,003)	0
Available-for-sale securities, estimated fair value	825,349	1,817,737
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(18,413)	(66,539)
Total Fixed Maturities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	175,800	4,806,737
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(5,370)	(210,640)
Available-for-sale securities, estimated fair value, 12 months or longer	1,919,820	3,512
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	(43,551)	(146)
Available-for-sale securities, estimated fair value	2,095,620	4,810,249
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(48,921)	(210,786)
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	6,302	144
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(123)	(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	6,302	144
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(123)	(4)
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	34,293	20,943
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(1,431)	(714)
Available-for-sale securities, estimated fair value, 12 months or longer	0	27,735
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	0	(400)
Available-for-sale securities, estimated fair value	34,293	48,678
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(1,431)	(1,114)
Total Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	40,595	21,087
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(1,554)	(718)
Available-for-sale securities, estimated fair value, 12 months or longer	0	27,735
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	0	(400)
Available-for-sale securities, estimated fair value	40,595	48,822
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	(1,554)	(1,118)
Short-Term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	314,995
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, less than 12 months	(1)
Available-for-sale securities, estimated fair value, 12 months or longer	0
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses, 12 months or longer	0
Available-for-sale securities, estimated fair value	314,995
Available-for-sale securities, gross unrealized holding and other-than-temporary impairment losses	$ (1)