LOSS AND LOSS ADJUSTMENT RESERVES (Activity in Liability for Loss and LAE Reserves) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Gross reserves, beginning-of-period	$ 540,367	$ 324,362
Less: reinsurance recoverable	(327,940)	(212,606)	$ (358,128)	$ (164,429)
Net reserves, beginning-of-period	182,239	159,933
Incurred loss, net of reinsurance, related to:
Current year	47,493	69,365
Prior year loss development (redundancy)	624	(117)
Ceded losses subject to offsetting experience account adjustments	(96)	(295)
Prior years	528	(412)
Amortization of acquisition fair value adjustment	(5)	(23)
Total incurred loss and LAE, net of reinsurance	48,016	68,930
Paid loss, net of reinsurance, related to:
Current year	24,669	13,371
Prior years	46,813	52,423
Total paid loss and LAE, net of reinsurance	71,482	65,794
Net reserves, end-of-period	158,773	163,069
Plus: reinsurance recoverable	327,940	212,606	$ 358,128	$ 164,429
Gross reserves, end-of-period	$ 486,713	$ 375,675