SEGMENT REPORTING (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Number of operating segments			1
Gross premiums written	$ 181,588	$ 128,205	$ 553,691	$ 387,234
Premiums Written, Gross as a percentage of Total Gross Premiums Written	100.00%	100.00%	100.00%	100.00%
Total Property
Segment Reporting Information [Line Items]
Gross premiums written	$ 48,882	$ 19,956	$ 130,302	$ 61,791
Premiums Written, Gross as a percentage of Total Gross Premiums Written	26.90%	15.60%	23.50%	15.90%
Commercial
Segment Reporting Information [Line Items]
Gross premiums written	$ 5,336	$ 6,768	$ 14,068	$ 22,068
Premiums Written, Gross as a percentage of Total Gross Premiums Written	2.90%	5.30%	2.50%	5.70%
Motor
Segment Reporting Information [Line Items]
Gross premiums written	$ 19,772	$ 10,316	$ 50,211	$ 28,416
Premiums Written, Gross as a percentage of Total Gross Premiums Written	10.90%	8.10%	9.10%	7.30%
Personal
Segment Reporting Information [Line Items]
Gross premiums written	$ 23,774	$ 2,872	$ 66,023	$ 11,307
Premiums Written, Gross as a percentage of Total Gross Premiums Written	13.10%	2.20%	11.90%	2.90%
Total Casualty
Segment Reporting Information [Line Items]
Gross premiums written	$ 92,873	$ 81,357	$ 312,368	$ 231,413
Premiums Written, Gross as a percentage of Total Gross Premiums Written	51.20%	63.50%	56.40%	59.80%
General Liability
Segment Reporting Information [Line Items]
Gross premiums written	$ 8,003	$ 5,252	$ 25,955	$ 23,824
Premiums Written, Gross as a percentage of Total Gross Premiums Written	4.40%	4.10%	4.70%	6.20%
Motor
Segment Reporting Information [Line Items]
Gross premiums written	$ 59,981	$ 61,226	$ 215,780	$ 161,938
Premiums Written, Gross as a percentage of Total Gross Premiums Written	33.00%	47.80%	39.00%	41.80%
Professional
Segment Reporting Information [Line Items]
Gross premiums written	$ 10,072	$ 4,822	$ 37,407	$ 27,237
Premiums Written, Gross as a percentage of Total Gross Premiums Written	5.60%	3.80%	6.70%	7.00%
Workers' Compensation
Segment Reporting Information [Line Items]
Gross premiums written	$ 14,817	$ 10,057	$ 33,226	$ 18,414
Premiums Written, Gross as a percentage of Total Gross Premiums Written	8.20%	7.80%	6.00%	4.80%
Total Specialty
Segment Reporting Information [Line Items]
Gross premiums written	$ 39,833	$ 26,892	$ 111,021	$ 94,030
Premiums Written, Gross as a percentage of Total Gross Premiums Written	21.90%	20.90%	20.10%	24.30%
Accident & Health
Segment Reporting Information [Line Items]
Gross premiums written	$ 22,608	$ 11,322	$ 57,387	$ 44,891
Premiums Written, Gross as a percentage of Total Gross Premiums Written	12.40%	8.80%	10.40%	11.60%
Financial
Segment Reporting Information [Line Items]
Gross premiums written	$ 13,737	$ 11,387	$ 38,771	$ 31,184
Premiums Written, Gross as a percentage of Total Gross Premiums Written	7.60%	8.90%	7.00%	8.10%
Marine
Segment Reporting Information [Line Items]
Gross premiums written	$ 1,427	$ 2,109	$ 5,743	$ 7,925
Premiums Written, Gross as a percentage of Total Gross Premiums Written	0.80%	1.60%	1.00%	2.00%
Other
Segment Reporting Information [Line Items]
Gross premiums written	$ 2,061	$ 2,074	$ 9,120	$ 10,030
Premiums Written, Gross as a percentage of Total Gross Premiums Written	1.10%	1.60%	1.70%	2.60%