RESERVE FOR LOSSES AND LOSS EXPENSES - Summary of Reserve for Losses and Loss Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Insurance Loss Reserves [Abstract]
Reserve for reported losses and loss expenses	$ 5,555,865	$ 5,539,971
Reserve for losses incurred but not reported	9,612,998	9,113,123
Reserve for losses and loss expenses	$ 15,168,863	$ 14,653,094	$ 13,926,766	$ 12,752,081