RESERVE FOR LOSSES AND LOSS EXPENSES - Average Annual Percentage Payout of Incurred Claims by Age, Net of Reinsurance (Details)	Dec. 31, 2024
Insurance | Property
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	31.20%
Year 2	40.20%
Year 3	13.20%
Year 4	5.70%
Year 5	0.60%
Year 6	0.50%
Year 7	(0.60%)
Year 8	1.70%
Year 9	0.70%
Year 10	1.10%
Insurance | Accident and health
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	54.20%
Year 2	33.20%
Year 3	6.00%
Year 4	1.90%
Year 5	1.70%
Year 6	0.50%
Year 7	1.10%
Year 8	(0.20%)
Year 9	(1.30%)
Year 10	0.20%
Insurance | Marine and aviation
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	18.50%
Year 2	25.80%
Year 3	20.50%
Year 4	9.40%
Year 5	4.00%
Year 6	3.30%
Year 7	3.90%
Year 8	1.10%
Year 9	(0.60%)
Year 10	0.00%
Insurance | Cyber
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	10.60%
Year 2	24.00%
Year 3	17.10%
Year 4	17.20%
Year 5	7.70%
Year 6	5.50%
Year 7	8.10%
Year 8	7.20%
Year 9	1.90%
Year 10	(0.20%)
Insurance | Professional lines
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	3.50%
Year 2	11.00%
Year 3	15.50%
Year 4	12.50%
Year 5	12.50%
Year 6	12.00%
Year 7	7.80%
Year 8	4.80%
Year 9	8.10%
Year 10	2.00%
Insurance | Credit and political risk
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	9.60%
Year 2	56.70%
Year 3	5.80%
Year 4	3.80%
Year 5	3.30%
Year 6	1.50%
Year 7	(6.00%)
Year 8	(11.10%)
Year 9	0.00%
Year 10	0.00%
Insurance | Liability
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	3.40%
Year 2	10.70%
Year 3	14.80%
Year 4	20.20%
Year 5	13.60%
Year 6	10.70%
Year 7	7.90%
Year 8	4.90%
Year 9	2.40%
Year 10	2.10%
Reinsurance | Accident and health
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	38.70%
Year 2	46.40%
Year 3	13.10%
Year 4	0.40%
Year 5	0.40%
Year 6	0.70%
Year 7	0.50%
Year 8	(0.10%)
Year 9	(0.70%)
Year 10	0.00%
Reinsurance | Marine and aviation
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	8.20%
Year 2	26.40%
Year 3	19.10%
Year 4	15.80%
Year 5	10.10%
Year 6	4.40%
Year 7	1.60%
Year 8	1.60%
Year 9	1.10%
Year 10	2.20%
Reinsurance | Professional lines
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	1.70%
Year 2	5.60%
Year 3	11.30%
Year 4	12.60%
Year 5	12.60%
Year 6	12.20%
Year 7	10.10%
Year 8	9.10%
Year 9	6.40%
Year 10	6.30%
Reinsurance | Liability
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	4.70%
Year 2	9.80%
Year 3	11.50%
Year 4	12.60%
Year 5	11.20%
Year 6	10.40%
Year 7	8.10%
Year 8	7.10%
Year 9	6.50%
Year 10	5.60%
Reinsurance | Credit and surety
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	25.60%
Year 2	20.40%
Year 3	12.60%
Year 4	8.30%
Year 5	2.10%
Year 6	1.10%
Year 7	0.40%
Year 8	0.50%
Year 9	(1.10%)
Year 10	0.30%
Reinsurance | Motor
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	23.20%
Year 2	18.30%
Year 3	9.70%
Year 4	6.80%
Year 5	6.00%
Year 6	5.60%
Year 7	6.20%
Year 8	3.00%
Year 9	2.50%
Year 10	2.10%
Reinsurance | Agriculture
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	10.50%
Year 2	59.20%
Year 3	19.10%
Year 4	2.40%
Year 5	(0.50%)
Year 6	1.10%
Year 7	(0.10%)
Year 8	(0.60%)
Year 9	0.20%
Year 10	0.00%
Reinsurance | Run-off lines
Short-duration Insurance Contracts, Historical Claims Duration [Line Items]
Year 1	24.00%
Year 2	28.80%
Year 3	17.20%
Year 4	10.30%
Year 5	6.00%
Year 6	3.30%
Year 7	2.70%
Year 8	0.60%
Year 9	0.70%
Year 10	0.60%