REINSURANCE (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Premiums written
Net premiums written	$ 180,534	$ 176,243	$ 480,554	$ 469,458
Premiums earned
Net premiums earned	155,190	152,181	449,514	441,364
Losses and settlement expenses incurred
Net losses and settlement expenses incurred	119,576	108,173	323,089	296,102
Affiliated Entity [Member]
Premiums written
Assumed	153,900	146,289	415,426	393,418
Ceded	(124,567)	(121,884)	(323,096)	(322,427)
Premiums earned
Assumed	128,325	122,058	375,601	359,985
Ceded	(98,449)	(98,765)	(298,108)	(295,166)
Losses and settlement expenses incurred
Assumed	81,324	85,476	259,111	233,505
Ceded	(75,248)	(63,294)	(227,404)	(172,481)
Non Affiliated Entity [Member]
Premiums written
Direct	122,665	119,849	312,809	311,542
Assumed	40,288	40,813	111,598	114,808
Ceded	(11,752)	(8,824)	(36,183)	(27,883)
Premiums earned
Direct	96,547	96,730	287,821	284,281
Assumed	39,688	40,564	113,933	115,122
Ceded	(10,921)	(8,406)	(29,733)	(22,858)
Losses and settlement expenses incurred
Direct	62,745	59,831	198,317	167,827
Assumed	58,229	27,999	107,091	74,085
Ceded	$ (7,474)	$ (1,839)	$ (14,026)	$ (6,834)
Property and casualty insurance [Member]
Reinsurance Transactions For Insurance Companies, by Product Segment [Line Items]
Percentage of pool participation (in hundredths)	30.00%	30.00%	30.00%	30.00%
Premiums written
Net premiums written	$ 144,011	$ 138,904	$ 385,209	$ 370,704
Premiums earned
Net premiums earned	120,472	116,372	350,307	338,589
Losses and settlement expenses incurred
Net losses and settlement expenses incurred	74,039	81,643	231,067	225,207
Property and casualty insurance [Member] | Affiliated Entity [Member]
Premiums written
Assumed	153,900	146,289	415,426	393,418
Ceded	(123,355)	(120,614)	(319,459)	(318,617)
Premiums earned
Assumed	128,325	122,058	375,601	359,985
Ceded	(97,237)	(97,495)	(294,471)	(291,356)
Losses and settlement expenses incurred
Assumed	81,047	85,196	258,169	232,472
Ceded	(66,279)	(63,282)	(218,425)	(172,892)
Property and casualty insurance [Member] | Non Affiliated Entity [Member]
Premiums written
Direct	122,665	119,849	312,809	311,542
Assumed	1,333	1,221	3,542	3,430
Ceded	(10,532)	(7,841)	(27,109)	(19,069)
Premiums earned
Direct	96,547	96,730	287,821	284,281
Assumed	1,225	1,170	3,370	3,332
Ceded	(8,388)	(6,091)	(22,014)	(17,653)
Losses and settlement expenses incurred
Direct	62,745	59,831	198,317	167,827
Assumed	961	793	2,406	2,298
Ceded	(4,435)	(895)	(9,400)	(4,498)
Reinsurance [Member]
Premiums written
Net premiums written	36,523	37,339	95,345	98,754
Premiums earned
Net premiums earned	34,718	35,809	99,207	102,775
Losses and settlement expenses incurred
Net losses and settlement expenses incurred	45,537	26,530	92,022	70,895
Reinsurance [Member] | Affiliated Entity [Member]
Premiums written
Assumed	0	0	0	0
Ceded	(1,212)	(1,270)	(3,637)	(3,810)
Premiums earned
Assumed	0	0	0	0
Ceded	(1,212)	(1,270)	(3,637)	(3,810)
Losses and settlement expenses incurred
Assumed	277	280	942	1,033
Ceded	(8,969)	(12)	(8,979)	411
Reinsurance [Member] | Non Affiliated Entity [Member]
Premiums written
Direct	0	0	0	0
Assumed	38,955	39,592	108,056	111,378
Ceded	(1,220)	(983)	(9,074)	(8,814)
Premiums earned
Direct	0	0	0	0
Assumed	38,463	39,394	110,563	111,790
Ceded	(2,533)	(2,315)	(7,719)	(5,205)
Losses and settlement expenses incurred
Direct	0	0	0	0
Assumed	57,268	27,206	104,685	71,787
Ceded	$ (3,039)	$ (944)	$ (4,626)	$ (2,336)