QUARTERLY FINANCIAL RESULTS (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues
Gross premiums written	$ 138,960	$ 181,588	$ 174,889	$ 197,214	$ 148,838	$ 128,205	$ 92,237	$ 166,792	$ 692,651	$ 536,072	$ 502,124
Gross premiums ceded	(42,707)	(7,931)	(2,523)	(3,426)	(2,267)	(2,119)	(3,522)	(2,107)	(56,587)	(10,015)	(9,001)
Net premiums written	96,253	173,657	172,366	193,788	146,571	126,086	88,715	164,685	636,064	526,057	493,123
Change in net unearned premium reserves	44,832	(964)	(12,042)	(41,886)	(9,939)	(13,294)	36,867	(26,573)	(10,060)	(12,939)	(84,736)
Net premiums earned	141,085	172,693	160,324	151,902	136,632	112,792	125,582	138,112	626,004	513,118	408,387
Net investment income (loss) [net of related party expenses of $19,863, $24,543 and $19,246]	(16,214)	63,976	(39,149)	11,618	52,857	32,945	(38,054)	28,435	20,231	76,183	(281,924)
Other income (expense), net	(336)	(520)	303	(7)	(754)	(192)	282	(271)	(560)	(935)	(3,413)
Total revenues	124,535	236,149	121,478	163,513	188,735	145,545	87,810	166,276	645,675	588,366	123,050
Expenses
Loss and loss adjustment expenses incurred, net	122,658	168,918	106,016	104,812	97,304	81,467	111,376	90,668	502,404	380,815	317,097
Acquisition costs, net	35,089	38,011	45,429	43,211	34,243	25,844	35,484	38,963	161,740	134,534	116,207
General and administrative expenses	5,064	8,202	6,347	6,743	6,878	6,937	4,994	6,999	26,356	25,808	23,434
Total expenses	162,811	215,131	157,792	154,766	138,425	114,248	151,854	136,630	690,500	541,157	456,738
Income (loss) before income tax	(38,276)	21,018	(36,314)	8,747	50,310	31,297	(64,044)	29,646	(44,825)	47,209	(333,688)
Income tax (expense) benefit	342	(65)	295	(121)	(258)	(305)	258	(204)	451	(509)	1,755
Net income (loss) including non-controlling interest	(37,934)	20,953	(36,019)	8,626	50,052	30,992	(63,786)	29,442	(44,374)	46,700	(331,933)
Loss (income) attributable to non-controlling interest in related party joint venture	202	(1,078)	550	(252)	(856)	(981)	791	(773)	(578)	(1,819)	5,508
Net income (loss)	$ (37,732)	$ 19,875	$ (35,469)	$ 8,374	$ 49,196	$ 30,011	$ (62,995)	$ 28,669	$ (44,952)	$ 44,881	$ (326,425)
Earnings (loss) per share
Basic	$ (1.02)	$ 0.53	$ (0.96)	$ 0.22	$ 1.32	$ 0.80	$ (1.69)	$ 0.77	$ (1.21)	$ 1.20	$ (8.90)
Diluted	$ (1.02)	$ 0.53	$ (0.96)	$ 0.22	$ 1.31	$ 0.80	$ (1.69)	$ 0.77	$ (1.21)	$ 1.20	$ (8.90)
Weighted average number of ordinary shares used in the determination of earnings and loss per share
Weighted average shares outstanding - basic	37,023,895	37,345,985	37,025,703	37,341,338	37,381,714	37,323,575	37,281,392	37,107,039	37,002,260	37,267,145	36,670,466
Weighted Average Number of Shares Outstanding, Diluted	37,023,895	37,375,273	37,042,506	37,376,649	37,414,570	37,385,481	37,281,392	37,422,921	37,002,260	37,340,018	36,670,466