SEGMENT INFORMATION (DETAILS 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenue from External Customer [Line Items]
Net premiums earned	$ 941,911	$ 945,242	$ 945,873	$ 874,039	$ 856,049	$ 862,447	$ 850,603	$ 846,362	$ 3,707,065	$ 3,415,463	$ 3,314,961
Insurance [Member]
Revenue from External Customer [Line Items]
Net premiums earned									1,722,762	1,558,058	1,429,687
Insurance [Member] | Property [Member]
Revenue from External Customer [Line Items]
Net premiums earned									462,364	408,943	385,291
Insurance [Member] | Marine [Member]
Revenue from External Customer [Line Items]
Net premiums earned									179,057	171,165	152,123
Insurance [Member] | Terrorism [Member]
Revenue from External Customer [Line Items]
Net premiums earned									39,298	38,605	35,213
Insurance [Member] | Aviation [Member]
Revenue from External Customer [Line Items]
Net premiums earned									48,489	60,363	70,681
Insurance [Member] | Credit and political risk [Member]
Revenue from External Customer [Line Items]
Net premiums earned									68,192	87,103	97,680
Insurance [Member] | Professional lines [Member]
Revenue from External Customer [Line Items]
Net premiums earned									586,200	563,500	536,238
Insurance [Member] | Liability [Member]
Revenue from External Customer [Line Items]
Net premiums earned									110,623	86,873	89,555
Insurance [Member] | Accident and health [Member]
Revenue from External Customer [Line Items]
Net premiums earned									228,539	141,506	62,906
Reinsurance [Member]
Revenue from External Customer [Line Items]
Net premiums earned									1,984,303	1,857,405	1,885,274
Reinsurance [Member] | Catastrophe [Member]
Revenue from External Customer [Line Items]
Net premiums earned									380,199	375,088	456,858
Reinsurance [Member] | Property [Member]
Revenue from External Customer [Line Items]
Net premiums earned									350,970	351,470	356,022
Reinsurance [Member] | Professional lines [Member]
Revenue from External Customer [Line Items]
Net premiums earned									304,754	297,726	281,025
Reinsurance [Member] | Credit and surety [Member]
Revenue from External Customer [Line Items]
Net premiums earned									279,943	277,185	263,912
Reinsurance [Member] | Motor [Member]
Revenue from External Customer [Line Items]
Net premiums earned									221,844	237,006	202,830
Reinsurance [Member] | Liability [Member]
Revenue from External Customer [Line Items]
Net premiums earned									234,736	220,874	230,872
Reinsurance [Member] | Agriculture [Member]
Revenue from External Customer [Line Items]
Net premiums earned									126,490	17,116	15,031
Reinsurance [Member] | Engineering [Member]
Revenue from External Customer [Line Items]
Net premiums earned									66,243	68,402	65,727
Reinsurance [Member] | Other [Member]
Revenue from External Customer [Line Items]
Net premiums earned									$ 19,124	$ 12,538	$ 12,997