RESERVE FOR LOSSES AND LOSS EXPENSES (DETAILS) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Insurance Loss Reserves [Abstract]
Reserve for reported losses and loss expenses	$ 3,358,514	$ 3,253,080
Reserve for losses incurred but not reported	6,339,313	6,393,205
Reserve for losses and loss expenses	$ 9,697,827	$ 9,646,285	$ 9,596,797	$ 9,582,140