Investments (Tables)

6 Months Ended

Jun. 30, 2011

Available-for-sale Securities [Table Text Block]

			Included in Accumulated Other Comprehensive Income (“AOCI”)
					Gross Unrealized Losses
June 30, 2011 (U.S. dollars in thousands) (Unaudited)	Cost or Amortized Cost		Gross Unrealized Gains		Related to Changes In Estimated Fair Value			OTTI Included In Other Comprehensive Income (Loss)(1)			Fair Value
Fixed maturities
U.S. Government and Government- Related/Supported (2)	$	1,454,860	$	79,258	$	(15,306	)	$	—		$	1,518,812
Corporate (3) (4)		10,196,731		366,054		(223,974	)		(69,220	)		10,269,591
Residential mortgage-backed securities – Agency		5,506,311		181,501		(11,472	)		—			5,676,340
Residential mortgage-backed securities – Non-Agency		970,742		22,885		(108,719	)		(111,622	)		773,286
Commercial mortgage-backed securities		1,097,687		61,737		(5,529	)		(7,493	)		1,146,402
Collateralized debt obligations		884,809		10,816		(152,647	)		(7,021	)		735,957
Other asset-backed securities		992,550		13,341		(15,032	)		(7,086	)		983,773
U.S. States and political subdivisions of the States		1,445,473		32,450		(14,120	)		—			1,463,803
Non-U.S. Sovereign Government, Supranational and Government-Related/Supported (2)		2,556,325		58,694		(31,297	)		—			2,583,722
Total fixed maturities	$	25,105,488	$	826,736	$	(578,096	)	$	(202,442	)	$	25,151,686
Total short-term investments (3)	$	2,855,542	$	35,049	$	(38,768	)	$	—		$	2,851,823
Total equity securities	$	282,128	$	36,788	$	(221	)	$	—		$	318,695

			Included in Accumulated Other Comprehensive Income (“AOCI”)
					Gross Unrealized Losses
December 31, 2010 (U.S. dollars in thousands)	Cost or Amortized Cost		Gross Unrealized Gains		Related to Changes In Estimated Fair Value			OTTI Included In Other Comprehensive Income (Loss)(1)			Fair Value
Fixed maturities
U.S. Government and Government- Related/Supported (2)	$	2,052,551	$	98,889	$	(23,949	)	$	—		$	2,127,491
Corporate (3) (4)		10,352,806		353,308		(272,093	)		(73,138	)		10,360,883
Residential mortgage-backed securities – Agency		5,020,469		152,905		(8,628	)		—			5,164,746
Residential mortgage-backed securities – Non-Agency		1,256,741		26,356		(133,758	)		(128,251	)		1,021,088
Commercial mortgage-backed securities		1,135,075		55,852		(7,960	)		(10,460	)		1,172,507
Collateralized debt obligations		920,080		10,960		(188,563	)		(8,814	)		733,663
Other asset-backed securities		964,129		16,084		(23,218	)		(8,164	)		948,831
U.S. States and political subdivisions of the States		1,370,378		16,746		(35,447	)		—			1,351,677
Non-U.S. Sovereign Government, Supranational and Government- Related/Supported (2)		2,642,657		63,511		(42,875	)		—			2,663,293
Total fixed maturities	$	25,714,886	$	794,611	$	(736,491	)	$	(228,827	)	$	25,544,179
Total short-term investments (3)	$	2,058,447	$	19,606	$	(29,446	)	$	—		$	2,048,607
Total equity securities	$	56,737	$	28,083	$	(53	)	$	—		$	84,767

Available For Sale Securities Continuous Unrealised Loss Position [Text Block]

	Less than 12 months					Equal to or greater than 12 months
June 30, 2011 (U.S. dollars in thousands) (Unaudited)	Fair Value		Gross Unrealized Losses (1)			Fair Value		Gross Unrealized Losses (1)
Fixed maturities and short-term investments:
U.S. Government and Government-Related/Supported	$	418,953	$	(16,616	)	$	126,530	$	(17,873	)
Corporate (2) (3)		2,429,908		(86,771	)		1,374,319		(214,481	)
Residential mortgage-backed securities – Agency		948,527		(8,417	)		13,606		(3,099	)
Residential mortgage-backed securities – Non-Agency		98,770		(27,038	)		573,274		(193,306	)
Commercial mortgage-backed securities		106,076		(3,694	)		43,771		(9,328	)
Collateralized debt obligations		3,597		(2,239	)		713,897		(157,429	)
Other asset-backed securities		183,539		(2,107	)		191,212		(22,226	)
U.S. States and political subdivisions of the States		554,520		(10,783	)		50,105		(3,337	)
Non-U.S. Sovereign Government, Supranational and Government-Related		822,154		(7,510	)		368,376		(33,052	)
Total fixed maturities and short-term investments	$	5,566,044	$	(165,175	)	$	3,455,090	$	(654,131	)
Total equity securities	$	10,343	$	(221	)	$	—	$	—

	Less than 12 months					Equal to or greater than 12 months
December 31, 2010 (U.S. dollars in thousands)	Fair Value		Gross Unrealized Losses (1)			Fair Value		Gross Unrealized Losses (1)
Fixed maturities and short-term investments:
U.S. Government and Government-Related/Supported	$	307,082	$	(25,482	)	$	117,394	$	(10,417	)
Corporate (2) (3)		2,271,887		(80,276	)		1,627,083		(275,023	)
Residential mortgage-backed securities – Agency		280,390		(6,736	)		34,186		(1,913	)
Residential mortgage-backed securities – Non-Agency		40,052		(2,574	)		843,168		(259,715	)
Commercial mortgage-backed securities		46,419		(2,472	)		69,475		(15,967	)
Collateralized debt obligations		2,500		(51	)		715,295		(197,535	)
Other asset-backed securities		122,548		(1,619	)		226,946		(33,546	)
U.S. States and political subdivisions of the States		734,893		(30,033	)		40,907		(5,452	)
Non-U.S. Sovereign Government, Supranational and Government-Related		459,686		(5,116	)		418,322		(40,837	)
Total fixed maturities and short-term investments	$	4,265,457	$	(154,359	)	$	4,092,776	$	(840,405	)
Total equity securities	$	158	$	(53	)	$	—	$	—

Schedule Of Fixed Maturities By Contractual Maturity [Text Block]

	(Unaudited) June 30, 2011 (1)				December 31, 2010 (1)
(U.S. dollars in thousands)	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Due after 1 through 5 years	$	8,381,553	$	8,543,992	$	8,807,515	$	8,936,246
Due after 5 through 10 years		3,614,498		3,728,269		3,733,842		3,857,055
Due after 10 years		3,657,338		3,563,667		3,877,035		3,710,043
		15,653,389		15,835,928		16,418,392		16,503,344
Residential mortgage-backed securities – Agency		5,506,311		5,676,340		5,020,469		5,164,746
Residential mortgage-backed securities – Non-Agency		970,742		773,286		1,256,741		1,021,088
Commercial mortgage-backed securities		1,097,687		1,146,402		1,135,075		1,172,507
Collateralized debt obligations		884,809		735,957		920,080		733,663
Other asset-backed securities		992,550		983,773		964,129		948,831
Total mortgage and asset-backed securities		9,452,099		9,315,758		9,296,494		9,040,835
Total	$	25,105,488	$	25,151,686	$	25,714,886	$	25,544,179

Schedule Of Fixed Maturity Credit Losses Other Than Temporary Impairments [Text Block]

	OTTI related to Credit Losses recognized in earnings
(U.S. dollars in thousands) (Unaudited)	Three Months Ended June 30,						Six Months Ended June 30,
	2011			2010			2011			2010
Opening balance	$	330,170		$	551,748		$	426,372		$	537,121
Credit loss impairment recognized in the current period on securities not previously impaired		11,333			9,384			15,906			19,458
Credit loss impairments previously recognized on securities that matured, paid down, prepaid or were sold during the period		(38,316	)		(22,003	)		(164,027	)		(37,978	)
Credit loss impairments previously recognized on securities impaired to fair value during the period		—			(130,891	)		—			(130,891	)
Additional credit loss impairments recognized in the current period on securities previously impaired		13,339			22,591			38,798			50,218
Accretion of credit loss impairments previously recognized due to an increase in cash flows expected to be collected		(682	)		(7,788	)		(1,205	)		(14,887	)
Balance, June 30	$	315,844		$	423,041		$	315,844		$	423,041

Gain (Loss) on Investments [Table Text Block]

	Three Months Ended June 30,						Six Months Ended June 30,
(U.S. dollars in thousands) (Unaudited)	2011			2010			2011			2010
Gross realized gains	$	61,037		$	28,969		$	88,179		$	63,142
Gross realized losses		(70,581	)		(90,355	)		(164,160	)		(160,704	)
Net realized (losses) on investments	$	(9,544	)	$	(61,386	)	$	(75,981	)	$	(97,562	)

Schedule Of Fixed Maturities By Held Maturity [Text Block]

June 30, 2011 (U.S. dollars in thousands) (Unaudited)	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Fixed maturities
U.S. Government and Government Related/Supported	$	10,832	$	61	$	(2	)	$	10,891
Corporate		1,369,317		6,349		(25,531	)		1,350,135
Residential mortgage-backed securities – Non-Agency		84,730		321		(257	)		84,794
Other asset-backed securities		293,700		3,345		(1,266	)		295,779
Non-U.S. Sovereign Government, Supranational and Government-Related		1,084,792		14,318		(21,204	)		1,077,906
Total fixed maturities held to maturity	$	2,843,371	$	24,394	$	(48,260	)	$	2,819,505

December 31, 2010 (U.S. dollars in thousands)	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Fixed maturities
U.S. Government and Government Related/Supported	$	10,541	$	164	$	(9	)	$	10,696
Corporate		1,337,797		6,370		(16,325	)		1,327,842
Residential mortgage-backed securities – Non-Agency		82,763		634		(546	)		82,851
Other asset-backed securities		287,109		1,134		(1,410	)		286,833
Non-U.S. Sovereign Government, Supranational and Government- Related		1,010,125		30,680		(6,401	)		1,034,404
Total fixed maturities held to maturity	$	2,728,335	$	38,982	$	(24,691	)	$	2,742,626

Held-to-maturity Securities [Table Text Block]

	(Unaudited) June 30, 2011				December 31, 2010
(U.S. dollars in thousands)	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Due less than 1 year	$	5,071	$	5,117	$	—	$	—
Due after 1 through 5 years		132,267		133,449		125,449		125,416
Due after 5 through 10 years		414,130		412,748		348,797		346,494
Due after 10 years		1,913,473		1,887,618		1,884,217		1,901,032
		2,464,941		2,438,932		2,358,463		2,372,942
Residential mortgage-backed securities – Non-Agency		84,730		84,794		82,763		82,851
Other asset-backed securities		293,700		295,779		287,109		286,833
Total mortgage and asset-backed securities		378,430		380,573		369,872		369,684
Total	$	2,843,371	$	2,819,505	$	2,728,335	$	2,742,626

Fair Value, Option, Quantitative Disclosures [Table Text Block]

June 30, 2011 (U.S. dollars in thousands)	Weighted Average Life	Amortized Cost		Fair Value		Average Rating	Change in Fair Value during the six months ended June 30, 2011
Synthetic CDO	1.80	$	8,942	$	10,880	B	$	(8,392	)
CDO Squared	6.00		8,982		15,754	B		967
	4.29	$	17,924	$	26,634	B	$	(7,425	)

December 31, 2010 (U.S. dollars in thousands)	Weighted Average Life	Amortized Cost		Fair Value		Average Rating	Change in Fair Value during the six months ended December 31, 2010
Synthetic CDO	3.87	$	32,175	$	41,105	BB	$	8,930
CDO Squared	6.04		8,491		12,198	B		3,707
	4.37	$	40,666	$	53,303	BB	$	12,637