RESERVE FOR LOSSES AND LOSS EXPENSES - Prior year development (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior year favorable (unfavorable) adjustments	$ 32,410	$ 15,909	$ 78,900
Insurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior year favorable (unfavorable) adjustments	18,360	8,937	53,302
Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior year favorable (unfavorable) adjustments	$ 14,049	$ 6,972	$ 25,598