RESERVE FOR LOSSES AND LOSS EXPENSES (DETAILS 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Additional Information Related to Net Incurred Losses [Line Items]
Current year net loss and loss expenses			$ 1,098,168	$ 1,686,013
Net favorable prior year reserve development	74,612	51,550	119,840	101,254
Short Tail Lines Insurance And Reinsurance Business [Member]
Additional Information Related to Net Incurred Losses [Line Items]
Net favorable prior year reserve development	68,000	29,000	87,000	66,000
Professional Lines Insurance And Reinsurance Business [Member]
Additional Information Related to Net Incurred Losses [Line Items]
Net favorable prior year reserve development	4,000	22,000	27,000	38,000
Catastrophe [Member]
Additional Information Related to Net Incurred Losses [Line Items]
Current year net loss and loss expenses				$ 627,000