SEGMENT REPORTING Geographic information (Details) - USD ($) $ 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
Revenue from External Customer [Line Items]
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 by geographical area as a percentage of total gross premiums									100.00%		100.00%		100.00%
U.S. and Caribbean
Revenue from External Customer [Line Items]
Gross premiums written									$ 606,510		$ 432,144		$ 383,236
Gross premiums by geographical area as a percentage of total gross premiums									87.60%		80.60%		76.30%
Worldwide (1)
Revenue from External Customer [Line Items]
Gross premiums written									$ 86,714	[1]	$ 97,810		$ 104,336
Gross premiums by geographical area as a percentage of total gross premiums									12.50%	[1]	18.20%	[1]	20.80%
Europe (2)
Revenue from External Customer [Line Items]
Gross premiums written									$ (612)		$ 6,250		$ 14,085
Gross premiums by geographical area as a percentage of total gross premiums									(0.10%)		1.20%		2.80%
Asia (2)
Revenue from External Customer [Line Items]
Gross premiums written									$ 39		$ (132)		$ 467
Gross premiums by geographical area as a percentage of total gross premiums									0.00%		0.00%		0.10%

[1] “Worldwide” is comprised of contracts that reinsure risks in more than one geographic area and do not specifically exclude the U.S.