Reinsurance (Tables)

12 Months Ended

Dec. 31, 2012

Reinsurance Disclosures [Abstract]

Effect of reinsurance

	Premiums Written						Premiums Earned
	Year Ended December 31,						Year Ended December 31,
(U.S. dollars in thousands)	2012		2011		2010		2012		2011		2010
Direct	$	4,733,518	$	4,714,588	$	4,398,753	$	4,604,327	$	4,624,557	$	4,535,626
Assumed		2,441,612		2,183,696		1,862,578		2,393,490		2,179,555		1,837,528
Ceded		(1,218,109)		(1,464,896)		(1,261,743)		(1,231,835)		(1,477,000)		(1,342,017)
Net	$	5,957,021	$	5,433,388	$	4,999,588	$	5,765,982	$	5,327,112	$	5,031,137

Analysis of losses, loss expenses and future policy benefit reserves recoverables

(U.S. dollars in thousands)	2012		2011
P&C operations	$	3,361,702	$	3,629,928
Life Operations		20,399		25,020
Total unpaid losses and loss expenses recoverable	$	3,382,101	$	3,654,948

Ceded credit risk by reinsurer

Name of Reinsurer	Reinsurer Financial Strength Rating		% of Total
Munich Reinsurance Company		AA-/Stable		25.4%
Swiss Reinsurance Company		AA-/Stable		11.0%
Lloyd's Syndicate		A+/Stable		8.0%
Swiss Re Europe S.A.		AA-/Stable		5.5%
Transatlantic Reinsurance Company		A+/Stable		4.0%

Ratings profile of reinsurers

Reinsurer Financial Strength Rating	% of Total
AAA		1.2%
AA		53.1%
A		37.1%
BBB		0.3%
BB and below		0.0%
Captives		6.1%
Not Rated		0.2%
Other		2.0%
Total		100.0%