Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2012

Fair Value, by Balance Sheet Grouping [Table Text Block]

March 31, 2012 (U.S. dollars in thousands)	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Collateral and Counterparty Netting			Balance at March 31, 2012
Assets
U.S. Government and Government - Related/Supported	$	-	$	2,233,820	$	-	$	-		$	2,233,820
Corporate (1) (2)		-		10,186,687		33,305		-			10,219,992
Residential mortgage-backed securities – Agency (“RMBS - Agency”)		-		5,353,596		39,795		-			5,393,391
Residential mortgage-backed securities – Non-Agency (“RMBS - Non-Agency”)		-		632,054		-		-			632,054
Commercial mortgage-backed securities (“CMBS”)		-		944,153		-		-			944,153
Collateralized debt obligations (“CDO”)		-		7,868		638,697		-			646,565
Other asset-backed securities (2)		-		1,409,732		16,410		-			1,426,142
U.S. States and political subdivisions of the States		-		1,768,182		-		-			1,768,182
Non-U.S. Sovereign Government, Provincial, Supranational and Government-Related		-		4,027,363		-		-			4,027,363
Total fixed maturities, at fair value	$	-	$	26,563,455	$	728,207	$	-		$	27,291,662
Equity securities, at fair value (3)		322,713		308,355		-		-			631,068
Short-term investments, at fair value (1)(4)		-		212,327		-		-			212,327
Total investments available for sale	$	322,713	$	27,084,137	$	728,207	$	-		$	28,135,057
Cash equivalents (5)		1,140,591		566,444		-		-			1,707,035
Other investments (6)		-		727,948		115,659		-			843,607
Other assets (7)(8)		-		116,301		-		(77,963	)		38,338
Total assets accounted for at fair value	$	1,463,304	$	28,494,830	$	843,866	$	(77,963	)	$	30,724,037
Liabilities
Financial instruments sold, but not yet purchased (9)	$	-	$	21,575	$	-	$	-		$	21,575
Other liabilities (7)(8)		-		26,248		40,630		(512	)		66,366
Total liabilities accounted for at fair value	$	-	$	47,823	$	40,630	$	(512	)	$	87,941

December 31, 2011 (U.S. dollars in thousands)	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Other Unobservable Inputs (Level 3)		Collateral and Counterparty Netting			Balance at December 31, 2011
Assets
U.S. Government and Government - Related/Supported	$	-	$	1,990,983	$	-	$	-		$	1,990,983
Corporate (1) (2)		-		10,084,804		23,818		-			10,108,622
RMBS – Agency		-		5,347,365		32,041		-			5,379,406
RMBS – Non-Agency		-		641,815		-		-			641,815
CMBS		-		974,835		-		-			974,835
CDO		-		7,751		650,851		-			658,602
Other asset-backed securities (2)		-		1,323,697		16,552		-			1,340,249
U.S. States and political subdivisions of the States		-		1,797,378		-		-			1,797,378
Non-U.S. Sovereign Government, Provincial, Supranational and Government-Related		-		3,298,135		-		-			3,298,135
Total fixed maturities, at fair value (2)	$	-	$	25,466,763	$	723,262	$	-		$	26,190,025
Equity securities, at fair value (3)		239,175		229,022		-		-			468,197
Short-term investments, at fair value (1)(4)		-		359,063		-		-			359,063
Total investments available for sale	$	239,175	$	26,054,848	$	723,262	$	-		$	27,017,285
Cash equivalents (5)		1,686,101		1,068,264		-		-			2,754,365
Other investments (6)		-		547,598		113,959		-			661,557
Other assets (7)(8)		-		143,622		-		(77,888	)		65,734
Total assets accounted for at fair value	$	1,925,276	$	27,814,332	$	837,221	$	(77,888	)	$	30,498,941
Liabilities
Financial instruments sold, but not yet purchased (9)	$	-	$	20,844	$	-	$	-		$	20,844
Other liabilities (7)(8)		-		16,871		42,644		(809	)		58,706
Total liabilities accounted for at fair value	$	-	$	37,715	$	42,644	$	(809	)	$	79,550

Fair Value, Assets And Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Text Block]

	Level 3 Assets and Liabilities - Three Months Ended March 31, 2012
(U.S. dollars in thousands)	Corporate			RMBS - Agency			RMBS - Non Agency		CMBS		CDO
Balance, beginning of period	$	23,818		$	32,041		$	-	$	-	$	650,851
Realized gains (losses)		(18	)		13			-		-		(1,649	)
Movement in unrealized gains (losses)		(315	)		(79	)		-		-		33,116
Purchases and issuances		9,076			36			-		-		-
Sales and settlements		(137	)		(2,348	)		-		-		(43,621	)
Transfers into Level 3		881			10,132			-		-		-
Transfers out of Level 3		-			-			-		-		-
Fixed maturities to short-term investments classification change		-			-			-		-		-
Balance, end of period	$	33,305		$	39,795		$	-	$	-	$	638,697
Movement in total gains (losses) above relating to instruments still held at the reporting date	$	(332	)	$	(54	)	$	-	$	-	$	29,202

	Level 3 Assets and Liabilities - Three Months Ended March 31, 2012
(U.S. dollars in thousands)	Other asset- backed securities			Non-US Sovereign Government, Provincial, Supranational and Government Related		Short-term investments		Other investments			Derivative Contracts - Net
Balance, beginning of period	$	16,552		$	-	$	-	$	113,959		$	(42,644	)
Realized gains (losses)		21			-		-		1,925			-
Movement in unrealized gains (losses)		(163	)		-		-		899			2,014
Purchases and issuances		-			-		-		1,317			-
Sales and settlements		-			-		-		(2,441	)		-
Transfers into Level 3		-			-		-		-			-
Transfers out of Level 3		-			-		-		-			-
Fixed maturities to short-term investments classification change		-			-		-		-			-
Balance, end of period	$	16,410		$	-	$	-	$	115,659		$	(40,630	)
Movement in total gains (losses) above relating to instruments still held at the reporting date	$	(431	)	$	-	$	-	$	(313	)	$	2,014

	Level 3 Assets and Liabilities - Three Months Ended March 31, 2011
(U.S. dollars in thousands)	Corporate			RMBS - Agency			RMBS - Non Agency			CMBS			CDO
Balance, beginning of period	$	36,866		$	30,255		$	4,964		$	1,623		$	721,572
Realized gains (losses)		-			-			-			(889	)		(652	)
Movement in unrealized gains (losses)		46			38			6			1,040			26,045
Purchases and issuances		10,629			11,460			-			-			-
Sales and settlements		(1,970	)		(1,269	)		(301	)		(17	)		(4,414	)
Transfers into Level 3		4,397			3,944			-			-			-
Transfers out of Level 3		(15,083	)		(11,441	)		(1,334	)		-			-
Fixed maturities to short-term investments classification change		-			-			-			-			-
Balance, end of period	$	34,885		$	32,987		$	3,335		$	1,757		$	742,551
Movement in total gains (losses) above relating to instruments still held at the reporting date	$	51		$	38		$	6		$	151		$	25,393

	Level 3 Assets and Liabilities - Three Months Ended March 31, 2011
(U.S. dollars in thousands)	Other asset- backed securities			Non-US Sovereign Government, Provincial, Supranational and Government Related			Short-term investments		Other investments			Derivative Contracts - Net
Balance, beginning of period	$	24,650		$	3,667		$	-	$	133,717		$	(39,195	)
Realized gains (losses)		(452	)		-			-		-			-
Movement in unrealized gains (losses)		2,818			-			-		9,771			2,449
Purchases and issuances		-			-			-		1,864			-
Sales and settlements		(9,650	)		-			-		(518	)		(64	)
Transfers into Level 3		-			-			-		-			-
Transfers out of Level 3		(4,995	)		(3,667	)		-		-			-
Fixed maturities to short-term investments classification change		-			-			-		-			-
Balance, end of period	$	12,371		$	-		$	-	$	144,834		$	(36,810	)
Movement in total gains (losses) above relating to instruments still held at the reporting date	$	1,912		$	-		$	-	$	8,707		$	2,449

Schedule Of Financial Instruments Not Carried at Fair Value [Text Block]

	March 31, 2012				December 31, 2011
	Carrying Value		Fair Value		Carrying Value		Fair Value
(U.S. dollars in thousands)
Fixed maturities, held to maturity	$	2,769,800	$	2,994,429	$	2,668,978	$	2,895,688
Other investments - structured transactions		316,889		291,151		323,705		297,124
Financial Assets	$	3,086,689	$	3,285,580	$	2,992,683	$	3,192,812
Deposit liabilities	$	1,590,188	$	1,817,915	$	1,608,108	$	1,809,812
Notes payable and debt		1,674,653		1,772,525		2,275,327		2,340,148
Financial Liabilities	$	3,264,841	$	3,590,440	$	3,883,435	$	4,149,960