RESERVE FOR LOSSES AND LOSS EXPENSES - Prior year development (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior years	$ 6,808	$ 2,655	$ 12,126	$ 8,767
Insurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior years	6,427	420	7,932	4,251
Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior years	$ 381	$ 2,235	$ 4,194	$ 4,516