RESERVE FOR LOSSES AND LOSS EXPENSES (DETAILS 3) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Additional Information Related to Net Incurred Losses [Line Items]
Net favorable (adverse) prior year reserve development	$ 45,125	$ 64,538	$ 165,804	$ 193,385
Short Tail Lines Insurance And Reinsurance Business [Member]
Additional Information Related to Net Incurred Losses [Line Items]
Net favorable (adverse) prior year reserve development	38,000	61,000	112,000	162,000
Professional Lines Reinsurance Business [Member]
Additional Information Related to Net Incurred Losses [Line Items]
Net favorable (adverse) prior year reserve development	1,000	10,000	25,000	22,000
Professional Lines Insurance Business [Member]
Additional Information Related to Net Incurred Losses [Line Items]
Net favorable (adverse) prior year reserve development	(15,000)		(16,000)
Credit and Surety Business [Member]
Additional Information Related to Net Incurred Losses [Line Items]
Net favorable (adverse) prior year reserve development	7,000		19,000
Credit And Political Risk Insurance Business [Member]
Additional Information Related to Net Incurred Losses [Line Items]
Net favorable (adverse) prior year reserve development			(15,000)
Liability and Motor Reinsurance Business [Member]
Additional Information Related to Net Incurred Losses [Line Items]
Net favorable (adverse) prior year reserve development	20,000	8,000	64,000	19,000
Liability Insurance Business [Member]
Additional Information Related to Net Incurred Losses [Line Items]
Net favorable (adverse) prior year reserve development	$ (6,000)	$ (14,000)	$ (23,000)	$ (14,000)