RESERVES FOR LOSSES AND LOSS SETTLEMENT EXPENSES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Gross liability for losses and loss settlement expenses at beginning of year	$ 1,421,754	$ 1,312,483	$ 1,224,183
Ceded losses and loss settlement expenses	(68,536)	(57,094)	(59,871)
Net liability for losses and loss settlement expenses at beginning of year	1,353,218	1,255,389	1,164,312
Losses and loss settlement expenses incurred for claims occurring during
Current year	887,119	835,507	785,778
Prior years	(17,652)	(5,335)	(54,167)
Total incurred	869,467	830,172	731,611
Losses and loss settlement expense payments for claims occurring during
Current year	354,635	333,975	306,032
Prior years	421,762	398,368	334,502
Total paid	776,397	732,343	640,534
Net liability for losses and loss settlement expenses at end of year	1,446,288	1,353,218	1,255,389
Ceded loss and loss settlement expenses	131,843	68,536	57,094
Gross liability for losses and loss settlement expenses at end of year	$ 1,578,131	$ 1,421,754	$ 1,312,483