Debt and financing Arrangements (Details 1) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Components of financial expenses
Finance expenses	$ 16,361	$ 13,218	$ 30,362	$ 28,369
2006 Junior Subordinated Deferrable Debentures [Member]
Components of financial expenses
Finance expenses	3,228	3,589	6,816	7,177
2007 Junior Subordinated Deferrable Debentures [Member]
Components of financial expenses
Finance expenses	3,028	3,028	6,057	6,057
2010 Senior Notes Due 2040 [Member]
Components of financial expenses
Finance expenses	5,597	5,597	11,194	9,575
Credit Facilities [Member]
Components of financial expenses
Finance expenses	1,589	1,109	3,313	2,420
AlphaCat Re 2011 fees [Member]
Components of financial expenses
Finance expenses	2,919	0	2,919	0
Talbot Fal Facility [Member]
Components of financial expenses
Finance expenses	0	(89)	63	333
Talbot other interest [Member]
Components of financial expenses
Finance expenses	0	(16)	0	59
Talbot third party FAL facility [Member]
Components of financial expenses
Finance expenses	$ 0	$ 0	$ 0	$ 2,748