LOSS AND LOSS ADJUSTMENT RESERVES - (Schedule of Activity in Liability for Loss and LAE Reserves) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Liability for Future Policy Benefits [Abstract]
Gross reserves, beginning-of-period	$ 230,515	$ 158,110	$ 97,706
Less: reinsurance recoverable	98,345	40,412	7,496
Net reserves, beginning-of-period	132,170	117,698	90,210
Incurred loss, net of reinsurance, related to:
Current year	231,133	245,545	201,704
Prior year loss development	2,166	13,926	13,156
Ceded losses under retrospectively rated quota-share	(4,883)	(11,914)	(17,050)
Prior years	(2,717)	2,012	(3,894)
Total incurred loss and LAE, net of reinsurance	228,416	247,557	197,810
Paid loss, net of reinsurance, related to:
Current year	155,462	160,945	123,364
Prior years	75,290	72,140	46,958
Total paid loss and LAE, net of reinsurance	230,752	233,085	170,322
Net reserves, end-of-period	129,834	132,170	117,698
Plus: reinsurance recoverable	166,396	98,345	40,412
Gross reserves, end-of-period	$ 296,230	$ 230,515	$ 158,110