RESERVE FOR LOSSES AND LOSS EXPENSES - Reserve for Losses and Loss Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Insurance Loss Reserves [Abstract]
Reserve for reported losses and loss expenses	$ 5,433,903	$ 5,559,261
Reserve for losses incurred but not reported	11,785,026	10,874,757
Reserve for losses and loss expenses	$ 17,218,929	$ 16,434,018	$ 15,168,863	$ 14,653,094