SCHEDULE IV -- REINSURANCE (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
SCHEDULE IV -- REINSURANCE [Abstract]
Direct premiums									$ 470,158	$ 394,679	$ 370,499
Ceded to other companies									145,201	130,012	128,697
Assumed from other companies									3,188	11,344	21,533
Net	$ 97,075	$ 89,100	$ 67,996	$ 73,974	$ 69,141	$ 71,235	$ 68,726	$ 66,909	$ 328,145	$ 276,011	$ 263,335
% of amount assumed to net									1.00%	4.10%	8.00%
Retrocessions associated with premiums assumed from other companies									$ 0	$ 86	$ 562