RESERVE FOR LOSSES AND LOSS EXPENSES (DETAILS) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Reconciliation of Beginning and Ending Gross Unpaid Losses and Loss Expenses
Gross reserve for losses and loss expenses, beginning of period			$ 9,646,285	$ 9,596,797
Less reinsurance recoverable on unpaid losses, beginning of period			(2,031,309)	(1,890,280)
Net reserve for unpaid losses and loss expenses, beginning of period			7,614,976	7,706,517
Net incurred losses and loss expenses related to:
Current year			1,279,369	1,213,160
Prior years	$ (77,719)	$ (64,613)	(148,113)	(120,679)
Net incurred losses and loss expenses			1,131,256	1,092,481
Net paid losses and loss expenses related to:
Current year			(112,730)	(86,827)
Prior years			(966,589)	(915,124)
Net paid losses and loss expenses			(1,079,319)	(1,001,951)
Foreign exchange and other			(106,629)	(125,666)
Net reserve for unpaid losses and loss expenses, end of period	7,560,284	7,671,381	7,560,284	7,671,381
Reinsurance recoverable on unpaid losses, end of period	2,222,020	2,022,059	2,222,020	2,022,059
Gross reserve for losses and loss expenses, end of period	$ 9,782,304	$ 9,693,440	$ 9,782,304	$ 9,693,440