Investments (Summary Of Unrealized Appreciation (Depreciation) Of Available For Sale, Fixed Maturity And Equity Security Investments) (Details) - USD ($) $ in Thousands		Jun. 30, 2015	Dec. 31, 2014
Fixed Maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis, Total		$ 13,213,596	$ 12,831,159
Unrealized Appreciation		394,403	426,973
Unrealized Depreciation		(133,198)	(157,065)
Market Value		13,474,801	13,101,067
OTTI in AOCI	[1]	2,297	(6,910)
U.S. Treasury Securities And Obligations Of U.S. Government Agencies And Corporations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis, Total		336,763	221,052
Unrealized Appreciation		11,953	10,290
Unrealized Depreciation		(464)	(304)
Market Value		348,252	231,038
Obligations Of U.S. States And Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis, Total		712,000	783,129
Unrealized Appreciation		29,604	41,969
Unrealized Depreciation		(2,885)	(626)
Market Value		738,719	824,472
Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis, Total		4,942,119	4,626,002
Unrealized Appreciation		127,488	143,889
Unrealized Depreciation		(32,992)	(62,906)
Market Value		5,036,615	4,706,985
OTTI in AOCI	[1]	2,297	(6,910)
Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis, Total		451,680	340,761
Unrealized Appreciation		1,981	1,691
Unrealized Depreciation		(1,579)	(1,230)
Market Value		452,082	341,222
Commercial Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis, Total		298,660	231,439
Unrealized Appreciation		8,598	10,675
Unrealized Depreciation		(1,798)	(429)
Market Value		305,460	241,685
Agency Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis, Total		2,181,733	2,157,182
Unrealized Appreciation		37,251	37,555
Unrealized Depreciation		(10,026)	(11,573)
Market Value		2,208,958	2,183,164
Non-Agency Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis, Total		1,347	2,734
Unrealized Appreciation		47	54
Unrealized Depreciation		(45)	(57)
Market Value		1,349	2,731
Foreign Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis, Total		1,321,212	1,488,144
Unrealized Appreciation		59,975	71,177
Unrealized Depreciation		(33,148)	(26,866)
Market Value		1,348,039	1,532,455
Foreign Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis, Total		2,968,082	2,980,716
Unrealized Appreciation		117,506	109,673
Unrealized Depreciation		(50,261)	(53,074)
Market Value		3,035,327	3,037,315
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis, Total		147,512	148,326
Unrealized Appreciation		3,322	3,831
Unrealized Depreciation		(13,318)	(11,947)
Market Value		$ 137,516	$ 140,210

[1] Represents the amount of OTTI recognized in AOCI. Amount includes unrealized gains and losses on impaired securities relating to changes in the value of such securities subsequent to the impairment measurement date.