LOSSES AND LOSS EXPENSES (Tables)

12 Months Ended

Dec. 31, 2011

Schedule of Unpaid losses and loss expenses [Text Block]

Year Ended December 31 (U.S. dollars in thousands)	2011		2010
Reserve for reported losses and loss expenses	$	8,153,585	$	8,510,605
Reserve for losses incurred but not reported		12,460,316		12,021,002
Unpaid losses and loss expenses	$	20,613,901	$	20,531,607

Schedule of Net losses and loss expenses incurred [Text Block]

Year Ended December 31 (U.S. dollars in thousands)	2011			2010			2009
Loss and loss expenses payments	$	4,911,737		$	4,309,523		$	5,138,951
Change in unpaid losses and loss expenses		260,631			(141,589	)		(1,148,495	)
Change in unpaid losses and loss expenses recoverable		(28,442	)		(117,120	)		441,397
Paid loss recoveries		(1,065,535	)		(839,014	)		(1,263,016	)
Net losses and loss expenses incurred	$	4,078,391		$	3,211,800		$	3,168,837

Analysis of paid and unpaid losses and loss expenses [Text Block]

(U.S. dollars in thousands)	2011			2010			2009
Unpaid losses and loss expenses at beginning of year	$	20,531,607		$	20,823,524		$	21,650,315
Unpaid losses and loss expenses recoverable		3,649,290			3,557,391			3,964,836
Net unpaid losses and loss expenses at beginning of year		16,882,317			17,266,133			17,685,479
Increase (decrease) in net losses and loss expenses incurred in respect of losses occurring in:
Current year		4,363,258			3,584,662			3,453,577
Prior years		(284,867	)		(372,862	)		(284,740	)
Total net incurred losses and loss expenses		4,078,391			3,211,800			3,168,837
Exchange rate effects		(130,533	)		(125,107	)		287,752
Less net losses and loss expenses paid in respect of losses occurring in:
Current year		589,870			442,262			439,638
Prior years		3,256,332			3,028,247			3,436,297
Total net paid losses		3,846,202			3,470,509			3,875,935
Net unpaid losses and loss expenses at end of year		16,983,973			16,882,317			17,266,133
Unpaid losses and loss expenses recoverable		3,629,928			3,649,290			3,557,391
Unpaid losses and loss expenses at end of year	$	20,613,901		$	20,531,607		$	20,823,524

Net (favorable) adverse prior years loss development of the loss and loss expense reserves [Text Block]

(U.S. dollars in millions)	2011			2010			2009
Insurance segment	$	(76.5	)	$	(127.4	)	$	(62.9	)
Reinsurance segment		(208.4	)		(245.5	)		(221.8	)
Total	$	(284.9	)	$	(372.9	)	$	(284.7	)

Schedule Of Net Favorable Adverse Prior Year Development Relating To Insurance Segment [Table Text Block]

(U.S. dollars in millions)	2011			2010			2009
Property	$	(8.9	)	$	(23.5	)	$	(50.7	)
Casualty and Professional		(47.1	)		(105.2	)		(41.0	)
Specialty and Other		(20.5	)		1.3			28.8
Total	$	(76.5	)	$	(127.4	)	$	(62.9	)

Schedule of Favorable Adverse Prior Year Development Relating To Reinsurance Segment [Table Text Block]

(U.S. dollars in millions)	2011			2010			2009
Property and other short-tail lines	$	(64.3	)	$	(145.8	)	$	(142.5	)
Casualty and other		(144.1	)		(99.7	)		(79.3	)
Total	$	(208.4	)	$	(245.5	)	$	(221.8	)

Reconciliation of unpaid losses and loss expenses related to asbestos and environmental exposure claims [Text Block]

Year Ended December 31,	2011			2010			2009
(U.S. dollars in thousands)
Net unpaid losses and loss expenses at beginning of year	$	84,075		$	100,922		$	111,860
Net incurred losses and loss expenses		(41	)		(130	)		(312	)
Less net paid losses and loss expenses		6,256			16,718			10,626
Net increase (decrease) in unpaid losses and loss expenses		(6,297	)		(16,848	)		(10,938	)
Net unpaid losses and loss expenses at end of year		77,778			84,075			100,922
Unpaid losses and loss expenses recoverable at end of year		134,323			142,037			151,963
Gross unpaid losses and loss expenses at end of year	$	212,101		$	226,112		$	252,885

Number of open claim files for potential asbestos and environmental claims [Text Block]

	Asbestos Claims			Environmental Claims
Total number of claims outstanding at December 31, 2008		1,546			548
New claims reported in 2009		221			38
Claims resolved in 2009		(330	)		(102	)
Total number of claims outstanding at December 31, 2009		1,437			484
New claims reported in 2010		125			31
Claims resolved in 2010		(362	)		(98	)
Total number of claims outstanding at December 31, 2010		1,200			417
New claims reported in 2011		106			36
Claims resolved in 2011		(268	)		(91	)
Total number of claims outstanding at December 31, 2011		1,038			362