SEGMENT INFORMATION (DETAILS 3) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenue from External Customer [Line Items]
Net premiums earned	$ 921,879	$ 934,415	$ 946,990	$ 902,340	$ 921,812	$ 919,341	$ 941,211	$ 904,053	$ 3,705,625	$ 3,686,417	$ 3,870,999
Insurance [Member]
Revenue from External Customer [Line Items]
Net premiums earned									1,777,321	1,798,191	1,830,544
Insurance [Member] | Property [Member]
Revenue from External Customer [Line Items]
Net premiums earned									426,918	432,587	444,197
Insurance [Member] | Marine [Member]
Revenue from External Customer [Line Items]
Net premiums earned									150,046	183,696	178,229
Insurance [Member] | Terrorism [Member]
Revenue from External Customer [Line Items]
Net premiums earned									33,279	36,818	35,876
Insurance [Member] | Aviation [Member]
Revenue from External Customer [Line Items]
Net premiums earned									44,980	45,659	41,192
Insurance [Member] | Credit and political risk [Member]
Revenue from External Customer [Line Items]
Net premiums earned									57,964	63,583	63,095
Insurance [Member] | Professional Lines [Member]
Revenue from External Customer [Line Items]
Net premiums earned									510,806	596,430	629,365
Insurance [Member] | Liability [Member]
Revenue from External Customer [Line Items]
Net premiums earned									169,182	161,614	146,819
Insurance [Member] | Accident and health [Member]
Revenue from External Customer [Line Items]
Net premiums earned									384,146	277,804	291,771
Reinsurance [Member]
Revenue from External Customer [Line Items]
Net premiums earned									1,928,304	1,888,226	2,040,455
Reinsurance [Member] | Catastrophe [Member]
Revenue from External Customer [Line Items]
Net premiums earned									199,825	216,020	325,307
Reinsurance [Member] | Property [Member]
Revenue from External Customer [Line Items]
Net premiums earned									272,403	306,083	312,443
Reinsurance [Member] | Professional Lines [Member]
Revenue from External Customer [Line Items]
Net premiums earned									289,868	310,915	336,058
Reinsurance [Member] | Credit and surety [Member]
Revenue from External Customer [Line Items]
Net premiums earned									252,210	250,208	263,013
Reinsurance [Member] | Motor [Member]
Revenue from External Customer [Line Items]
Net premiums earned									318,863	299,883	268,678
Reinsurance [Member] | Liability [Member]
Revenue from External Customer [Line Items]
Net premiums earned									332,479	297,000	289,223
Reinsurance [Member] | Agriculture [Member]
Revenue from External Customer [Line Items]
Net premiums earned									142,501	129,346	164,628
Reinsurance [Member] | Engineering [Member]
Revenue from External Customer [Line Items]
Net premiums earned									62,833	61,043	61,143
Reinsurance [Member] | Marine and Other [Member]
Revenue from External Customer [Line Items]
Net premiums earned									$ 57,322	$ 17,728	$ 19,962