INVESTMENTS IN AFFILIATES (Tables)

12 Months Ended

Dec. 31, 2011

Schedule of Investments in and Advances to Affiliates, Schedule of Investments [Table Text Block]

Year ended December 31, (U.S. dollars in thousands)	2011		2010
Investment fund affiliates	$	768,851	$	829,059
Operating affiliates		283,878		298,122
Total investment affiliates	$	1,052,729	$	1,127,181

Equity Investement In Investment Fund Affiliates And Equity In Net Income Loss From Such Affiliates [Table Text Block]

Year ended December 31, 2011: (U.S. dollars in thousands, except percentages)	XL Group Investment									Combined Funds
		Carrying Value		Equity in Net Income (Loss) for the Year			Weighted Average XL Percentage Ownership			Total Net Assets (Estimated) (2)
Alternative Funds (1):
Arbitrage		$	123,969	$	1,291			3.4	%	$	3,678,904
Directional			217,779		9,154			6.0	%		3,619,272
Event Driven			229,956		(60	)		3.1	%		7,472,680
Multi-Style			425		(9	)		17.6	%		2,410
Total alternative funds			572,129		10,376			3.9	%		14,773,266
Private equity funds (1)			196,722		15,877			5.1	%		3,820,497
		$	768,851	$	26,253			4.1	%	$	18,593,763

Year ended December 31, 2010: (U.S. dollars in thousands, except percentages)	XL Group Investment							Combined Funds
	Carrying Value		Equity in Net Income (Loss) for the Year		Weighted Average XL Percentage Ownership			Total Net Assets (Estimated) (2)
Alternative Funds (1):
Arbitrage	$	156,511	$	9,477		4.1	%	$	3,797,962
Directional		166,644		5,972		5.9	%		2,819,306
Event Driven		261,252		7,605		2.5	%		10,267,525
Multi-Style		787		30		8.1	%		9,688
Total alternative funds		585,194		23,084		3.5	%		16,894,481
Private equity funds (1)		243,865		28,018		5.5	%		4,408,189
	$	829,059	$	51,102		3.9	%	$	21,302,670

Schedule Of Equity Investment In Operating Fund Affiliates And Equity In Net Income Loss From Such Affiliates Disclosure [Text Block]

Year ended December 31, 2011: (U.S. dollars in thousands)	XL Investment					Combined Investee Summarized Financial Data (Estimated) (1)
	Carrying Value		Equity in Net Income (Loss) for the Year			Total Assets		Total Liabilities		Total Revenue (Loss)		Net Income (Loss)
(U.S. dollars in thousands)
Operating affiliates:
Financial operating affiliates	$	732	$	(1,018	)	$	11,957,534	$	11,931,662	$	12,564	$	1,115
Other strategic operating affiliates		153,955		20,891			1,295,921		967,264		348,831		48,641
Investment manager affiliates (2)		129,191		56,913			601,511		38,349		319,984		222,260
Total	$	283,878	$	76,786		$	13,854,966	$	12,937,275	$	681,379	$	272,016

Year ended December 31, 2010: (U.S. dollars in thousands)	XL Investment				Combined Investee Summarized Financial Data (Estimated) (1)
	Carrying Value		Equity in Net Income (Loss) for the Year		Total Assets		Total Liabilities		Total Revenue (Loss)			Net Income (Loss)
(U.S. dollars in thousands)
Operating affiliates:
Financial operating affiliates	$	1,750	$	53,031	$	6,212,583	$	6,179,978	$	(688	)	$	(15,641	)
Other strategic operating affiliates		122,266		28,161		1,075,578		772,572		274,786			48,792
Investment manager affiliates		174,106		40,180		654,229		70,816		375,384			348,615
Total	$	298,122	$	121,372	$	7,942,390	$	7,023,366	$	649,482		$	381,766