REINSURANCE (Premiums Written and Earned) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Premiums written [Abstract]
Direct									$ 605,485	$ 493,770	$ 377,156
Ceded									(285,986)	(268,516)	(201,998)
Net premiums written									319,499	225,254	175,158
Premiums earned [Abstract]
Direct									565,423	432,234	313,075
Ceded									(305,551)	(222,214)	(142,170)
Net premiums earned	$ 75,425	$ 69,405	$ 60,045	$ 54,997	$ 53,721	$ 62,286	$ 49,227	$ 44,786	$ 259,872	$ 210,020	$ 170,905