LOSS AND LOSS ADJUSTMENT RESERVES (Narrative) (Details) - USD ($) $ in Thousands	1 Months Ended	9 Months Ended
	Jul. 31, 2016	Sep. 30, 2018	Sep. 30, 2017
Liability for Future Policy Benefit, by Product Segment [Line Items]
Claim and claim adjustment expenses incurred related to current year		$ 159,998	$ 191,747
Claim and claim adjustment expenses incurred related to prior year		(3,900)	(3,064)
Reinsurance Programs | Florida
Liability for Future Policy Benefit, by Product Segment [Line Items]
Claim and claim adjustment expenses incurred related to current year		$ 300	$ 8,300
Quota Share Treaties | Florida | Property Insurance Product Line
Liability for Future Policy Benefit, by Product Segment [Line Items]
Percentage of property quota share reinsurance treaty	30.00%	10.00%