LOSS AND LOSS ADJUSTMENT RESERVES - (Schedule of Activity in Liability for Loss and LAE Reserves) (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 reserves, beginning-of-period	$ 324,362	$ 296,230	$ 230,515
Less: reinsurance recoverable	(164,429)	(166,396)	(98,345)
Net reserves, beginning-of-period	159,933	129,834	132,170
Net reserves from the Maison Companies acquisition	0	11,825	0
Incurred loss, net of reinsurance, related to:
Current year	358,952	262,118	231,133
Prior year loss development	18,367	13,460	2,166
Ceded losses under retrospectively rated quota-share	(816)	(2,489)	(4,883)
Prior years	17,551	10,971	(2,717)
Amortization of acquisition fair value adjustment	(54)	(9)	0
Total incurred loss and LAE, net of reinsurance	376,449	273,080	228,416
Paid loss, net of reinsurance, related to:
Current year	253,344	173,313	155,462
Prior years	100,799	81,493	75,290
Total paid loss and LAE, net of reinsurance	354,143	254,806	230,752
Net reserves, end-of-period	182,239	159,933	129,834
Plus: reinsurance recoverable	358,128	164,429	166,396
Gross reserves, end-of-period	$ 540,367	$ 324,362	$ 296,230